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Full text of "Contributions from the Botanical Laboratory and the Morris Arboretum"

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Vol. V 1919 No. 



CONTRIBUTIONS 



FROM THE 



Botanical Laboratory 



OF THE 



University of Pennsylvania 



University of Pennsyi,vania 

PHIIvADELPHIA 

1919 




CONTENTS OF VOLUME V, NO. 1. 



Page 

1. The Macroscopic and Microscopic Structure of some Hybrid 

Sarracenias Compared with that of their Parents. By 

Alice Mary Russell, B.S., M.S. (With plates i, ii, iii, iv, v.) 3 

2. A Comparative Study of the Structure and Saphrophytism 

of the Pyrolaceae and Monotropaceae with Reference 
to their Derivation from the Ericaceae, By Margaret 
W. Henderson, B.S., M.A 42 



Vol. V 1919 No. 



CONTRIBUTIONS 



FROM THE 



Botanical Laboratory 



OF THE 



University of Pennsylvania 



University of Pennsylvania 

Philadelphia 

19x9 



The Macroscopic and Microscopic Structure of 

some Hybrid Sarracenias Compared with 

that of their Parents 



By Alice Mary Russell, B.S., M.S. 

[Thesis presented to the Faculty of the Graduate School in partial fulfillment of the 
Requirements for the Degree of Doctor of Philosophy.] 



CONTENTS 

Historical Review 4 

Natural Distribution of Species and Hybrids Selected for 

Study 8 

Comparison of Parents and Hybrids 

5. purpurea, S. flava, S. Cateshaei 9 

5. flava, S. Drummondii, S. Moorei i8 

5. Sledgei, S. Drummondii, S. areolata 24 

Comparison of Flowers 27 

Description of Structure of Glands 32 

Ovarian Gland Structure 33 

Conclusions 35 

Bibliography 39 

Description of Plates 40 

3 



Russell — Comparison of the Structure of Hybrid 



Historical Review 

Before Tournefort had named the genus Sarracena (i) and 
Linnaeus (2) had accepted the name, the group of the Sarra- 
cenias was already known to the early settlers in North America. 
They collected the plants and sent them to Europe as inter- 
esting exotics, where they were carefully described in botanical 
publications. As early as 1570, Lobel described specimens of 
the group which had come to his attention. Clusius (1601) (3) 
figures S. purpurea and Parkinson (4) copies his figure and 
adds a note which seems to indicate that he knew 5. flava as 
well. Concerning this plant, which he calls "The Hollow 
Leaved Strange Plant of Clusius," he writes: "This strange 
plant hath such strange leaves, as the like are seldome scene 
in any other that we know growing, for they are nine or ten 
or more, rising from the head of a small long roote, each by 
itselfe, being small below, and growing greater upward, with 
a belly as it were bunching forth, and a bowing backe, hollow 
at the upper end, with a peece thereon like a flappe, and like 
unto the flower of Aristolochia, or Birthwort, and round at 
the mouth like a halfe circle, full of great darke purplish veins 
on the inside; the whole leaf is of thicke substance almost like 
unto leather; among these leaves sprang a stalke but was broken 
short off, so that what flower or seed it bore could not be ob- 
served. This was sent to Clusius from Paris by one that re- 
ceived it from Lishbone in the same manner. But of late 
Master John Tradescant the younger found this very plant 
in Virginia, having his toppe thereon, which he brought home 
and groweth with him, which I here show you with Clusius 
his figure. The leaves are longer, narrower and not bellying 
out, and the flower is borne at the top of the roundish seed 
vessell." The specimen sent by Tradescant was probably 6'. 
flava. 

Plukenet (6) (7) was familiar with both S. flava and S. pur- 
purea, since he gives very accurate figures of both species. 

John Ray (8) gave a Latin translation of Parkinson's descrip- 
tion already quoted. The actual specimen described by him, 
however, was a natural hybrid between 5. flava and S. pur- 
purea, and was the first natural hybrid collected. (See below.) 



Sarracenias with that of Their Parents 5 

Tournefort named the genus Sarracena, in honor of Dr. 
Sarrasin of Quebec (i), and described one species, S. canadensis. 
Linnaeus accepted the genus name and described the two spe- 
cies long recognized, 5. flava and 5. purpurea. 

Walter, in 1788 (9), described and named two new species, 
S. minor and S. rubra. S. psittacina was added to the genus 
by Michaux in 1803 (11). Croom (12) described 5. Drum- 
mondii in 1835. 

Since the above time, only one new species has been added, 
5. Sledgei in 1906, by Macfarlane (17). 

A few of the botanical publications of this time review the 
genus as varying in composition: 

"Flore des Serres" (13) gives seven species : S. flava (L.), S. 
purpurea (L.), S. variolaris (= minor Walt. = adunca Smith), 
S. undulata (Den.), S. Drummondii (Cro.), S. rubra (Walt.), 
S. psittacina (Michx.) (= calceolata = pulchella (Croom)). Chap- 
man (14) gives all of the above except S. undulata, which he 
considers synonymous with 5. Drummondii. Hooker (15) men- 
tions eight species but does not enumerate them. Boulger 
(16), in reviewing the genus, has the six species: 5. purpurea, 
S. flava, S. rubra, S. Drummondii, S. psittacina, S. variolaris. 

During the latter half of the i8th century, Sarracenias were 
widely cultivated in European gardens. New varieties were 
eagerly sought for exhibition, many new forms were introduced 
from America and several artificial hybrids were produced. 
Since each exhibitor appended a name to his own product, a 
great confusion of names had arisen and a survey of the forms 
under cultivation became most necessary. Dr. Masters, there- 
fore, undertook the review in three numbers of the Gardeners' 
Chronicle for the year 1881 (18). Here he gives a key to the 
forms raised in English gardens and gives for each a short de- 
scription from living specimens furnished to him. The forms 
and species described by him are as follows: 

1. S. psittacina (Michx.) A. D. C. Prod. XVII, p. 4. 

2. S. purpurea (L.) A. D. C. Prod. XVII, p. 4. 

3. S. Chehoni X (Hort. Veitch, G. C. vol. 9, p. 11 {rubra X purpurea). 

4. 5. variolaris (Michx.) Croom. A. D. C. Prod. XVII, p. 6. 

5. S. Drummondii (Croom) A. D. C. Prod. XVII, p. 5 (var. alba G. C. 

vol. 10, p. 281). 

6. 5. undulata (Den.) = S. Drummondii (Croom) Rev. Hort. i, p. 126. 

Flore des Serres 7, A. D. C. Prod. XVII, p. 5. Index Amer. Bot. 
p. 40. 



6 Russell— Comparison of the Structure of Hybrid 

7. 5. rubra (Walt.) Flora Car. p. 152. (Croom) A. D. C. Prod. XVII, p. 4. 

var. acuminata (A. D. C. loc. sit.) var. Sweetii (A. D. C.) Wat. 
Index p. 40 = 5. minor (Sweet) = S. rubra (Planchon). 

8. 5. yZam (L.) Sp. PI. Ed. i, p. 510. A. D. C. Prod. XVII, p. 5. var. 

Catesbaei (Ell.) Bot. S. Car. = S.flava var. picta Hort. Bull. = S. 
Fildesii Hort. Williams. 

Var. ornata (Hort. Bull.). 

Var. Rugelii (Shuttleworth) = erythropus Hort. Bull., A. D. 
C. Prod. XVI, p. 6. 

Var. limbata (Hort Bull.). 

Var. maxima (Hort. Angl.). 

Var. cristata (Hort. Bull.). 

Var. atrosanguinea (Hort. Bull.). 

Var. minima (Hort. Angl.). 

9. 5. Moorei X (G. C. 1874, p. 702 = 5. Drummondii X S.flava). 

10. S. Stevensii X (G. C. 1874, p. 738) = S.flava X 5. purpurea). 

11. S. Williamsii X (Hort. Williams above 10). 

12. S. Popei X {S.flava X S. rubra). 

13. 5. melanorhoda X (Hort. Veitch. 5. purpurea X 5. Stevensii). 

14. S. formosa X (Hort. Veitch. S. psittacina X 5. variolaris). 

The above review constitutes the basis for the article on 
Sarracenias in Nicholson's Dictionary of Gardening (20). 

The history of the hybrids grown during this period is inter- 
esting. In 1874 the first artificial hybrid was produced and 
exhibited by Dr. Moore at the International Botanical Congress 
in Florence. An abstract of Dr. Moore's paper upon the pre- 
sentation of the hybrid is given in the Gardeners' Chronicle 
1874, p. 738. Of the plant, which had 5. flava as the female 
and S. Drummondii as the male parent, he writes: "The plant 
is as nearly as possible intermediate between those two noble 
species of the genus, and no hybrid which has hitherto come 
under my notice proves more decidedly than it does the marked 
influence of the pollen of one plant applied to the stigma of 
another. . . . During the months of April and May most of 
the species flower and produce young leaves, after perfecting 
which the plants rest six weeks or more, when some of the kinds 
produce a second crop of leaves which remain fresh during 
the winter and are more beautiful than those of the first crop. 
This is especially the case with 5. Drummondii. ... 5. flava 
does not make a second growth of leaves in so marked a manner, 
but rather inclines to rest during the winter months." "Now 
it is in the mixture of the leaves that the intermediate state 
of the hybrid is so strikingly exemplified. It makes a second 



Sarracenias with that of Their Parents 7 

growth of winter pitchers similar to 5. Drummondii, and these 
are nearly as highly colored, but they decay much sooner than 
those of the parent species and thus resemble more those of 
the female parent, S. flava. Further, the large stature of the 
plant, nearly two feet high, the purple color of the flowers, 
and, indeed, everything connected with it, shows that it holds 
an exactly intermediate rank between the parents." Shortly 
afterwards Messrs. Veitch and Sons were awarded a prize for a 
hybrid between S. flava (female) and S. purpurea (male), and 
named in honor of the gardener whose product it was, S. Stevensii. 
A hybrid of the same parentage, but of natural origin, was 
exhibited under the name 5. Williamsii, in honor of the man 
who discovered it among a mass of S. flava shipped to him from 
the Southern States (22). Other artificial hybrids were shortly 
afterwards exhibited and are noted above by Masters. 

The most recent review of the genus is that of Macfarlane 
in "Pflanzenreich" (23). All of the species and hybrids noted 
above are given, but a new species is here added, 5. Sledgei (17). 
Macfarlane reviewed and fully described the supposed species 
5. Cateshaei (24) in order to eliminate the confusion which had 
arisen through ascribing to it forms such as S. rubra, S. flava, 
etc., because of Elliot's meager description, and the misplacing 
of his type specimen. The plants used as type specimens by 
Macfarlane were first obtained through Dr. Sledge, of Mobile, 
who sent them north, where they were grown in the Sarracenia 
House at the University of Pennsylvania Botanical Garden. 
The pitchers and flowers were typical, Macfarlane found, of 
plants cultivated abroad under the names S. flava, var. cristata, 
S. flava, var. picta, or S. flava, var. Catesbaei. A visit to the 
region established the fact that these plants grew in pure stands 
and were indigenous to the locality, so they were used as type 
forms on which the description of the supposed species 5. Cates- 
baei was based. Later the type of Elliot for the above species 
was found in the Charleston Museum, and proved to be a 
specimen of the natural hybrid between 5. flava and S. purpurea. 
A new name was therefore applied to the genus described by 
Macfarlane, 5. Sledgei. In regard to the new species he writes: 
"So far as accurate records show, 5. Sledgei seems to be con- 
fined to the Gulf region between the Alabama River and Eastern 
Texas, over which area it may at times be extremely abundant. 



8 Russell—Comparison of the Structure of Hybrid 

It is here only associated with 5. psittacina and S. purpurea, 
both of which flower from one to two weeks later. In spite 
of this there is every likelihood that hybrids will in time be 
reported, for the flowers of all species last for 14 to 21 days" (17). 

Since the time this was written, the author himself has found 
S. Drummondii growing with 5. Sledgei, and with them quan- 
tities of the cross which he has named S. areolata. Macfarlane 
(26) gives the following note concerning this plant: 

"It is a frequent hybrid wherever both parents are present 
near each other. It is especially abundant near Mobile, Ala., 
and westward for thirty miles." 

Natural Distribution of Species and Hybrids Selected 

FOR Study 

Of the forms to be studied, 5. purpurea is the best known 
and most widely distributed (23). It is found from Labrador 
through Newfoundland, Quebec, Manitoba, Michigan, Wiscon- 
sin, and from thence southward to Indiana. Along the coast 
it extends from New England to Florida in the swampy regions 
back as far as the Alleghany Mountains. In the south it is 
plentiful about the Gulf region from Florida to Louisiana. 

5. flava has a more restricted distribution (23). It is more 
or less abundant from southern Virginia, through North and 
South Carolina, Georgia, Florida, and eastern Alabama. 

Therefore, the hybrid between these species might be found 
in the region from North Carolina to eastern Alabama. It is 
reported from Wilmington, N. C, and Ponce de Leon, Florida. 
Possibly additional localities may be reported from Georgia (23) 
and South Carolina. 

5. Drummondii is found only between south central Georgia 
and western Alabama (23). Since S. flava is never found west 
of the Alabama River, the hybrid would not be expected out- 
side of southern Georgia, Florida, and eastern Alabama. Speci- 
mens have been gathered in Georgia (Americus), in Florida 
(Milligan and Crestview), and from Alabama (Bay Minette 
and Deer Park). 

S. Sledgei, most recently described species, is limited to the 
region about the Gulf, west of the Alabama River (23). There 
are specimens preserved from Alabama, Louisiana, and east- 



Sarracenias with that of Their Parents g 

ern Texas. Additional localities may yet be reported. The 
hybrid, S. areolata, with S. Drummondii, is therefore to be 
sought only between Alabama River and western Alabama. 
It is especially plentiful at two points, Theodore, Alabama, 
where it was first found, and Deer Park. 

The above are the species and hybrids selected for study. 
The material used was from natural sources indicated above, 
transplanted to the University of Pennsylvania Botanical 
Garden. 

It might be well to note here the other natural hybrids re- 
ported by various collectors. Besides the above three, there 
are given (23; 17) : 

S.fiava X S. minor. 

S. minor X S. psittacina (grown in University of Pennsylvania). 

5. rubra X S. Drummondii. 

S. psittacina X 5. purpurea. 

S. rubra X 5. purpurea (grown in University of Pennsylvania). 

5. Drummondii X 5. purpurea (grown in University of Pennsylvania). 

5. Sledgei X 5. purpurea (grown in University of Pennsylvania). 

The study was limited to three groups, with one parent com- 
mon to two hybrids in order the better to ascertain the action 
of a given parental characteristic. 

Comparison of Parents and Hybrids 

Set I. S. purpurea, S. flava, and S. Cateshaei (S. Stevensii) 
A. Naked Eye Characters 

The general habit of 5. purpurea is shown well in PI. I, fig. i, 
with its inflated pitchers, and the decumbent leaves. S. flava 
presents a striking contrast to 5. purpurea (PI. I, fig. 2). The 
pitchers are erect, slender, and gradually expanded upwards. 
In the hybrid (PI. I, fig. 3) the pitchers lean at an angle of 45°, 
and are slightly inflated in their middle portion. 

In height the three forms present a wide range. 6". purpurea, 
the lowest, averages 12-15 cm., though specimens can be 
found 35 cm. in length. S. flava may be from 20-100 cm. high, 
but average pitchers measure 60-70 cm. from base to the tip 
of the lid. The hybrid averages 24-36 cm. in length. 

The "wing," or fused laminar faces in front of the pitcher 
proper, is wide in 5. purpurea (PI. I, fig. i) and tends to have 
an undulating margin. In 5. flava the wing is very narrow 



lo Russell — Comparison of the Structure of Hybrid 

(PI. I, fig. 2) and extends the whole pitcher length. In S. Cates- 
haei the wing is wider below, half as wide as in S. purpurea, 
and of much the same shape (PI. I, fig. 3). 

In S. purpurea the inflated pitcher is constricted below the 
rim around the mouth (PI. I, fig. i). In 5. flava the pitcher 
has no suggestion of a constriction, but rather expands widely 
at the rim. In 5. Catesbaei the pitcher is slightly constricted 
below the rim (PI. I, fig. i), although not so strongly as in S. 
purpurea. 

The color of the pitchers of 5. purpurea is: base green with 
a reddish network of veins over the outer pitcher surface, par- 
ticularly above. The lid is especially strongly marked with 
crimson-purple reticulations. (Variations: all green; with 
graded transitions to crimson-purple suffused over the surface 
almost uniformly.) 5. flava, in the most common type, has 
a greenish yellow pitcher and lid, the latter with a deep crim- 
son patch at its base. The marking is usually band shaped, 
about 1-2.5 cm. wide. (Variations: purplish veining on upper 
pitcher and lid; bright green pitcher; or entire pitcher and lid 
rich purple.) 5. Catesbaei shows a variety in coloration, accord- 
ing to the variations noted above in the parents. An average 
type represented in fig. 3 has a green pitcher with red-purple 
veinings, less heavily developed than in S. purpurea. The red 
banding in the throat of the S. flava parent is reproduced, but 
more dilute in color. (Variations: uniformly green, more pro- 
nounced purple markings, or entirely purplish.) 

The lid shape in the three forms exhibits a nearly balanced 
relation. In 6'. purpurea the lid is reniform, with an undulate 
margin (PI. I, fig. i). The lower lateral portions of the lid 
are prolonged into blunt lobes, which are bent forward about 
the mouth of the pitcher, so that it is open only from the front. 
Instead of overhanging the pitcher opening, the lid in this spe- 
cies is somewhat curved outwards. In S. flava, the lid is ovate- 
cordate, but prolonged in its median portion into a tip process. 
The sides of the lid are not lobed as deeply as in S. purpurea, 
but the slight auricles are here bent sharply backwards, expos- 
ing the throat of the pitcher. The lid slightly incurves above 
the orifice. S. Catesbaei (fig. 3) is very nearly intermediate 
in parental characteristics. The lid is more rounded in out- 
line than S. flava, but possesses a slight tip process, not as pro- 



Sarracenias with that of Their Parents II 

nounced as in 5". flava. The lobes are intermediate in size, 
in position also, since they stand straight out from the side of 
the pitcher. The margin of the lid is wavy, with looser undu- 
lations than in S. purpurea. The lid does not overhang the 
pitcher mouth, but is erect. 

B. Microscopic Study of the Pitchers 
I. Methods. 

Three methods were used in preparing the epidermal sur- 
faces described below. 

(a) Scrapings of fresh material were made, for comparison 
with treated material to gauge possible shrinkage, or seeming 
abnormalities. 

{h) Scrapings of material macerated in KOH. 

(c) Strips of pitcher parts were boiled in 25%-50% HNO3, 
to which a pinch of KCIO3 was added. When the material 
appeared white, or bleached, it was quickly placed in water. 
The mesophyl and subepidermal cells could be easily brushed 
off and both upper and lower epidermis could be mounted 
in acetic acid side by side for comparison; sealed with asphaltum. 
The nitric acid was not used in such strength that cell walls 
were affected. The delicate hair striations appear clearly in 
the photographs (PI. IV, figs. 15 and 16) made from such slides 
with the aid of the Edinger apparatus. 

Ordinary paraffin material, fixed in chrom-osmo-acetic or 
weak chrom-acetic, was used for sections mentioned. 

In counts given for a "field," it will be understood, unless 
distinctly stated otherwise, that the standard "field" is that 
of a No. 3 Bausch and Lomb eyepiece, and a No. 4 mm. Bausch 
and Lomb objective. 

Averages are based on 100 or more counts, and measurements 
on 200 or more. Corresponding portions of corresponding 
surfaces were carefully selected for comparison. 

Outer Epidermis of the Lid 

In all three forms, the outer epidermis of the lid shows cells 
that are roughly quadrangular, with wavy walls. Normal 
stomata are present, and simple unicellular hairs. In general 
these hairs point upwards toward the edge of the lid. Glands, 
similar to those of the interior pitcher area, are scattered over 
this outer surface somewhat irregularly. 



12 Russell — Comparison of the Structure of Hybrid 

In 5. fiava the epidermal cells are longer than broad (PI. Ill, 
fig. 9) with an angular wavy wall. Stomata are fairly numer- 
ous, seven to a field, and of the same size as within the pitcher 
(.035 X. 030 mm.). Glands are less numerous than within on 
the specially modified surfaces, one only to a field averagely. 
The unicellular hairs mentioned above are in 5. flava blunt, 
with a decided bending or hooking in some, while in others 
the axis is straight or merely slightly curved. They vary 
greatly in size, from mere knobs .01 mm. long to .1, .2, .3 mm. 
in length. PI. Ill, fig. 9 will show the range of size and shape 
in these hairs. It will be noted that in all the surface of the 
hair is raised in wart-like thickenings, which at times lie in 
lines parallel to the axis of the hair, and suggest the rough be- 
ginnings of the beautifully regular striae found on the hairs 
of the inner pitcher surfaces. There are three hairs to a field. 

The epidermal cells of S. purpurea (PI. Ill, fig. 8) are more 
rounded wavy in outline than in 5. fiava. The stomata are 
more numerous, 16-17 appearing in a field. The glands are 
but slightly more frequent than above, 1.5 to a field. The 
hairs are straight, and vary in size even more than in S. flava 
.1, .2, .3, .4, etc., to .5-.6 mm. They are not quite so numerous 
as the hairs of S. flava, only two to an average field. 

5. Catesbaei (PI. Ill, fig. 10) shows epidermal cells more 
closely resembling S. purpurea. The stomata are fairly inter- 
mediate in number — 11 per field. There is one gland per field 
about as in the parents. The hairs, of course, inherit the 
tendency to variability. Some hairs have the marked S. fiava 
tendency to bending, though not so strong. On the whole, 
the range of size is much as in S. flava from .1 to .3 mm. There 
is one hair per field, less than in either parent. 

Inner Lid Region 

The epidermal cells of the inner portion of the lid are in all 
cases irregular in shape. In S. purpurea they are about as long 
as broad (.065 x. 05 mm.) with very wavy wall. 

In 5. flava the hairs are numerous, and compress the epi- 
dermal cells without hairs into oblong cells (.05X.03 mm.) 
with walls but slightly wavy. S. Catesbaei shows cells resem- 
bling S. purpurea in size and shape (.06 x. 047 mm). 



Sarracenias with that of Their Parents 13 

Stomata are frequent on this surface. In these three forms 
they are of the same size, .035 x. 030 mm. In number they 
are noteworthy, 5. flava having seven to a field, 5. purpurea 
three, and the hybrid shows an intermediate number — five. 

Glands are numerous over this, the alluring, surface. In 
5. flava there are 3-4 glands per field, in S. purpurea 2-3. The 
hybrid averages less than three. 

This region is beset with more or less numerous long, stiff 
hairs, directed downward. These prevent the insects from 
pursuing any path other than that to the treacherously smooth 
conducting surface. The hairs are thickened in parallel ridges, 
varying in number according to the species. 

In S. flava (PI. IV, fig. 16) the hairs seem to be remarkably 
uniform in length. Measurements show that over 50% are 
.22 mm, long, while the remainder are .11 or .3 mm. in length. 
They are very numerous — lo-ii to an average field. 

5. purpurea (PI. IV, fig. 15) has hairs many times longer 
than in S. flava. Besides these, there are shorter hairs, but none 
as short as the longest hairs of S. flava. They vary — about 
50% are 1.3 mm. long, 20% are .6-.9 mm. in length, and the 
remainder are 1.8 mm. long or measure .9-1.0 mm. They are 
quite scattered, one hair base appearing in two fields. 

S. Cateshaei (PI. IV, fig. 17) has a variety of hairs, as has 5. 
purpurea. Some are short, resembling those of 5. flava, .2 m. 
long, while others approach the S. purpurea type — i mm. long. 
Over 50% are less than .4 mm. in length; 20% are .5-.6 mm. 
long; the rest measure fom .7 to i mm. Hairs of the length of 
both parents are represented, since the shorter hairs of S. pur- 
purea are .9-1 mm. in length, but by far the larger number of 
hairs are closer to the S. flava type. There are but two hairs per 
field. 

The lower part of the tube, representing the conducting 
surfaces in 5. flxiva and S. Catesbaei, and the glandular surface 
of S. purpurea, has an exterior epidermis of cells of the same 
character as those of the exterior of the lid. Hairs of the same 
character are present, but more infrequent than on the lid. 
These hairs point upwards, generally, toward the pitcher mouth, 
and become more numerous on the upper portion of the tube. 

Stomata are very numerous over this surface. In S. flava 
and S. purpurea there are 14-15 stomata to a field; in the hybrid 



14 Russell—Comparison of the Structure of Hybrid 

fewer — lo-ii. The glands present have a tendency to be 
distributed along the strong ridges above the veins, especially 
in 5. flava. Averages of counts from the surface between the 
veins run about .5 gland per field, while on the veins 2-3 glands 
appear in a field. In 5. purpurea, where the veins are not so 
emphasized, the glands are equally distributed over the outer 
surface, and there are two to a field. In 5. Catesbaei there 
are fewer glands than in S. flava — one to a field, though here 
there is a slight tendency for the glands to be more numerous 
over the veins. 

The ridges spoken of above are formed by the reinforcement 
of the larger bundles on their inner and outer faces with a deep 
sclerenchymatous development. Above such bundles the sub- 
epidermal and epidermal layers become thickened enormously, 
so that the whole thickened area stands out above the sur- 
rounding epidermis. The ridges are very marked in S. flava, 
are not shown in 5. purpurea, and are fairly conspicuous in 
S. Catesbaei. 

The epidermis above the bundles undergoes a peculiar trans- 
formation. In S. purpurea, the wavy walled epidermal cells 
become elongated above the bundles. In 5. flava, the epi- 
dermal cells are elongated, straight walled cells, much thick- 
ened. 5. Catesbaei has these cells elongated slightly, heavily 
thickened — in fact about intermediate in character. Along 
these lines of cells there are no stoma ta, nor hairs; therefore 
they form the easiest paths which the insects can pursue up- 
ward toward the rim of the pitcher. 

Conducting Surface 

Below the lid surface in all forms, the epidermal cells become 
gradually polygonal in shape, and the hair processes become 
shorter and sharper. Every cell becomes prolonged into a 
pointed projection directed downward. The cells thus form 
a scale-like slippery covering for the inner pitcher surface to 
a varying depth. In S. purpurea it forms a narrow band, 1-2 
cm. wide; while in 5. flava and 5. Catesbaei it extends over at 
least one-half of the pitcher depth. 

The conducting cells of these three forms are interesting 
in length relation. In 5. purpurea the tip process is but little 
more than a knob (PI. V, fig. 22) and the cell measures .05 mm. 



Sarracenias with that of Their Parents 15 

to the end of the projection. S.flava has a long, fine tip (PI. V, 
fig. 23) and the cell measures .07 mm. in length. The upper 
portion of the conducting surface of S. Cateshaei shows an ex- 
actly intermediate size .06 mm. (PI. V, fig. 24). These cells 
are all beautifully thickened with striae, as are the lid hairs. 

L. S. Pitcher Rim 

A longitudinal section through the rim of the pitcher men- 
tioned above shows an interesting relation. In S. purpurea 
the rim is rolled outward and under, in two turns. In 5. flava 
the rim is rolled over once, rather loosely. 5. Catesbaei is 
rolled over, and slightly curved around again, or is rolled once 
and half. 

The tip region in S. purpurea has three layers of thickened 
cells, while in 5. flava the whole tip region is thickened. 5. 
Cateshaei shows about an intermediate amount of thickening. 

The conducting cells, with their fine processes, do not begin 
to show in S. flava at the tip, but considerably below the tip 
on the outwardly rolling portion. 

Below the conducting cells in S. purpurea there are two layers 
of thickened cells, closely united to each other and to the epi- 
dermis. In S.flava there is but one such layer. In 5. Catesbaei 
there is one regular continuous layer adjoining the epidermis, 
and a second discontinuous layer below it. The mesophyl in 
S. purpurea is loose, with large thin-walled cells. 5". flava has 
a more compact and more shallow tissue than in S. purpurea. 
The mesophyl in S. Catesbaei is not so loose as that of S. pur- 
purea, nor so compact as that of 5. flava. 

The outer epidermis in all three forms is composed of thin- 
walled cells. The stomata have their guard cells raised above 
the level of the epidermis in all three. 

Below the outer epidermis is a region of regular large, thin- 
walled cells closely applied to each other. These cells form 
a false palisade tissue in the pitchers. In 6". flava there are 
3-4 layers of these cells; in S. purpurea 2-3 layers; in S. Cates- 
haei there are 2 layers. These cells contain numerous chloro- 
plasts, and form a continuous layer, except where interrupted 
by stomatal chambers. 

In S. purpurea, below the narrow conducting surface there 
is a wide expanse of glandular surface, reaching down to the 



1 6 Russell— Comparison of the Structure of Hybrid 

detentive. This region, absent in S. flava, is characterized 
by large regular wavy- walled cells with numerous glands — 
6.6 per field. These cells are smooth, without a suggestion 
of any hair process. The lower conducting area in the hybrid 
represents a crossing of the lower conducting area of S. flava 
with the glandular area of 5. purpurea. There is no marked 
difference between the upper and lower portions of the con- 
ducting surfaces in the hybrid, excepting for a tendency toward 
lengthening of the cell process, and for the presence of numerous 
glands. 

On the upper conducting regions of 5. flava there are 3 glands 
per field; in S. purpurea there are 4 per field; in S. Catesbaei 
2.9 per field in this region. The lower conducting surface in 
S. flava is devoid of glands; the glandular surface of 5. purpurea, 
as has been mentioned, has 6 glands per field; in the hybrid 
there are 3, about half as many as are on the glandular area in 
S. purpurea. 

The lengthening of the cell process noted above for the hybrid 
in this region may be due to the influence of the S. flava type 
of conducting cells, or merely be the exhibition of the tendency 
shown in all forms for the conducting cell process to become 
prolonged deep in the pitcher. 

In the extreme lower conducting and upper detentive sur- 
face, the hybrid presents an interesting condition. This region, 
which represents a crossing of glandular-detentive area of S. 
purpurea with conducting-detentive of S. flava, exhibits a most 
confused zone about 1-1.5 cm. wide. There are several types 
of cells shown in this region: 

First, normal conducting cells which become gradually elong- 
ated and give place to detentive surface cells. 

Second, cells intermediate in size and shape between the 
glandular surface cells of 5. purpurea, and the detentive sur- 
face cells of 5. flava. These are long narrow cells with wavy 
walls. They appear at first isolated as islands of two or more 
cells, in the lower conducting surface; becoming more numerous 
below, and gradually giving place to normal detentive-surface 
cells. These cells represent a blending of the glandular sur- 
face cells of S. purpurea, with the unmodified epidermal cells 
of the detentive surface of S. flava. 

Third, normal detentive surface cells, polygonal in shape, 
some bearing long hair processes. These appear isolated in 



Sarracenias with that of Their Parents 17 

the region where the blended detentive-glandular cells are most 
numerous. 

Fourth, normal glandular cells of S. purpurea. These cells 
are reproduced in patches, isolated, in the region of the detentive- 
glandular cells. 

Fifth, normal detentive epidermal cells with or without hair 
processes, intermediate between the types of 5. flava and S. 
purpurea. 

Sixth, normal glands; two per field. These occur down to the 
purely detentive zone, where they cease. 

A similar case, such as above, is presented in a hybrid be- 
tween S. minor, without a glandular area, and S. purpurea, 
and has been discussed shortly by Macfarlane (28). He con- 
siders that this region represents a modification of the upper 
detentive surface. In both hybrids it seems to be shown that 
the conducting-surface cells of one parent are incapable of 
blending with glandular surface cells of S. purpurea, since no 
wavy-walled cell with a prolongation characteristic of the con- 
ducting surface type ever appears. In other words, this rep- 
resents a clear case of the so-called bi-sexual hybrid (29), or 
of particulate inheritance (38). 

The detentive surface presents no such confused condition, 
rather a perfect blending, cell for cell. In this region, in these 
forms, there are no stomata nor glands present. In all, the 
epidermal cells are polygonal and contain a fair amount of 
tannin (30). The hair cells are remarkable in relation. In 
S. purpurea they are long — 1.5 mm. — and rather infrequent — 
.7 to a field. Those of S. flava are quite short — .37 mm. — 
but very numerous — 5.5 per field. In S. Catesbaei the hairs 
are intermediate in size and number, for they are .88 mm. long, 
with 2.8 per field. 

Lower Pitcher Region 

T. S. of pitcher at lowest part of tube shows in all a hollow 
cylindrical portion, representing the T. S. of the pitcher proper. 
From the front extends the more or less wide wing, representing 
the fused laminae (23). In the cylinder the bundles are dis- 
posed at intervals, larger and smaller alternating, with the 
xylem on the inner side, toward the pitcher cavity. In the 
wing, two rows of bundles face each other, xylem opposed to 



1 8 Russell—Comparison of the Structure of Hybrid 

xylem. The things especially to be noted in comparing parents 
and hybrids are: the number of the subepidermal layers of 
cells, the depth and character of the mesophyl tissue, the rela- 
tive amount of sclerenchymatous tissue developed on the 
inner and outer side of the bundles, the number of subdetentive 
layers. 

In all three forms, the outer epidermal cells are regular with 
heavily cutinized walls. The stomata have their guard cells 
slightly raised above the epidermal level. 

Below this are the subepidermal layers of cells rich in chloro- 
plasts, forming on the morphologically lower surface a false 
palisade. In 5. purpurea there are 3-4 layers of cells, large 
and thin-walled. In S. flava there are 4-5 layers of these cells. 
They are smaller and more compactly arranged. S. Catesbaei 
resembles more 6". purpurea in that there are three subepidermal 
layers, which have larger cells less compactly arranged than in 
S. flava. 

The mesophyl is in 5. purpurea deep and loose. The cells 
are large, and intercellular spaces are frequent. S. flava has 
a very narrow mesophyl zone. The cells are regularly arranged 
with few intercellular spaces. In 5. Catesbaei the mesophyl 
is deep and spongy as in S. purpurea. In the mesophyl the 
bundles are distributed. In 5. purpurea they ar'e not strongly 
reinforced with sclerenchyma tissue. In S. flava the rein- 
forcement is pronounced, and involves the subepidermal and 
epidermal layers as well in the larger bundles. In S. Catesbaei 
the development is about intermediate between the parents. 

There are two or more layers of cells below the detentive 
surface which are thickened together with the epidermis. It 
is this which forms the so-called "absorption zone" mentioned 
by Fenner (31) and others. The contents of these cells are 
either gathered into large masses, or broken up into finely 
granular substance. These layers give a strong positive reac- 
tion for tannin. In 5. purpurea there are 1-2 layers of sub- 
detentive cells. In 5. flava there are two layers. In 5. Cates- 
baei there are three layers. 

Set 2. S. flava, S. Drummondii and S. Moorei 

The second hybrid of the series, between 5. flava and S. 
Drummondii, was the first artificial hybrid between species 
of Sarracenias to be exhibited. Though it was named in honor 



Sarracenias with that of Their Parents 1 9 

of its exhibitor, Dr. David Moore (21), it was also widely known 
as S. Mandaiana, which name was applied to the natural hy- 
brid. 

Both parents are strong and beautiful types, and as one 
might expect, as already noted in Dr. Moore's paper, quoted 
above, the hybrid is also a striking form. It is intermediate 
in appearance between the parents where the parental char- 
acteristics are capable of blending; but exhibits an apparent 
marked divergence toward one parent where a single char- 
acteristic can be inherited. This is particularly noteworthy 
in the pale areas on the lid and tube of 5. Drummondii. 

S. Drummondii (PI. I, fig. 4) is, like 5. flava (PI. I, fig. 2), 
tall, strong, erect, with pitchers ranging from 30-90 cm. high. 
Average specimens usually measure 60-70 cm. 5. flava, it will 
be recalled, is about of the same height, S. Moorei (PI. II, 
fig. 5) is about 65-70 cm. high. 

In both parents and hybrid the pitchers are slender below, 
increasing gradually in width to the flaring rim. The pitchers 
of S. flava seem on the whole to be more robust than those of 
5. Drummondii, and the hybrid seems to resemble 5. flava, 
or to be even stronger. 

The wing is narrow in these three forms. In 5. flava it con- 
tinues undiminished up to the rim, while in 5. Drummondii 
it narrows down to a mere ridge some distance below the rim. 
S. Moorei has the wing narrowing down to a mere ridge, but 
closer to the rim than in S. Drummondii. 

The lids in these types form an interesting series. That of 
S. flava is ovate-cordate, with a strong median process, and a 
straight margin. S. Drummondii has an orbicular lid with a 
blunt apex, and a wavy margin. In S. Moorei the lid is nearly 
intermediate between ovate and orbicular, with a slightly wavy 
margin, and a tip process not so pronounced as in 5. flava. 

In color relation the hybrid is remarkably intermediate. 
The typical S. flava is pale green, excepting for the red throat 
marking. (Variations: purplish-veined lid, or with an entirely 
purple pitcher.) The pitchers in S. Drummondii are green 
below with white areolations over the lid and upper tube; the 
areas between the areolations are marked with red veinings. 
Ruddy forms of this occur. Not uncommonly there is a pale 
form with green pitcher below, while, above, the areolations 



20 Russell— Comparison of the Structure of Hybrid 

are so enlarged that they become confluent, and the whole 
upper portion appears dazzling white. To this variety has 
been given the name alba. The typical hybrid shows a green 
pitcher with white areolations over the lid and upper tube; 
together with the red throat of 5. flava, which is here lessened 
in intensity. There is also a hybrid (ii) noted with the white 
variety of 5. Drummondii named above. In it the hybrid is 
pale, with pronounced areolations, as in S. Drummondii. Where 
the ruddy varieties are crossed the hybrid is very beautifully 
colored. The throat and rim are velvety red, with white areo- 
lations and crimson veining over the lid and pitcher. 

Outer Surface of the Lid 

The outer epidermal cells of S. Drummondii (PI. Ill, fig. ii) 
are slightly angular-rounded in shape. The cell walls project 
upward into a slight rounded papilla. This has been noted 
by Macfarlane (28). The stomata are grouped in special tracts 
above the veins between the areolations on the lid. The glands 
are more numerous over this special region also, but are sparsely 
scattered over the entire surface. The hairs are short and 
blunt above the veins. Around the window areas the hairs 
are longer. 

In S. flava the cells are longer than broad, with wavy walls. 
The surface of the epidermis is flat, the hairs, stomata, and 
glands are quite evenly distributed over the entire surface of 
the lid. There is no suggestion of grouping of the stomata in 
any special region. 

The epidermal cells in the hybrid (PI. Ill, fig. 12) are squar- 
ish, with slightly wavy walls. There is very little or no swelling 
of the upper cell surface. The stomata are distributed in tracts, 
but these areas are wider, and the stomata are less closely 
grouped. There are spaces devoid of stomata as in 5. Drum- 
mondi, where the glands are sparsely distributed. The hairs 
are long and strong over these areolations. 

Inner Lid Surface 

On the inner surface of the lid of 5. Drummondii (PI. IV, 
fig. 18) the cells are wavy walled, measuring .06 x .05 mm. to 
.05 X .04 mm. See PI. IV, fig. 16 for the appearance of the 
lid cells of S. flava, already described above in detail. The cells 
of the lid of the hybrid are intermediate in shape (PI. IV, fig. 19). 



Sarracenias with that of Their Parents 21 

The stomata, as in the case of the previous hybrid, form 
an interesting series. S.flava has 7.25 per field, while S. Drum- 
mondii has very few — only .59 per field. The hybrid is inter- 
mediate, with 3.4 per field. The size of the stomata varies 
in these forms. In 5. flava they are .035 by .03 mm., in S. 
Drummondii they are large, .045 X .04 mm. In the hybrid 
the size is intermediate — .04 X .035 mm. 

The glands present the same curious phenomenon as before; 
that is, there are fewer in the hybrid than in either parent. 
S. flava has 3.4 per field, 5. Drummondii 4.2, while S. Moorei 
has but 2.4. 

The hairs of S.flava vary from .1 mm. to .3 mm., with .2 mm. 
as the average length. S. Drummondii has remarkably long, 
fine hairs. There are present besides small fine hairs. The 
length varies from 1.98 mm. in length to .44 mm. The average 
length is about 1.07 mm. with i per field. As in the former 
hybrid considered, S. Catesbaei, the S. flava parent exerts strong 
influence on the size of the hairs. The hairs of S. Moorei vary 
greatly in length; very few are over i mm. long, however. The 
average length is about .5 mm.; which is close to intermediate 
between the species. They are more frequent than in S. Drum- 
mondii, 2.3 per field, which is many times less than the hairs 
of S. flava. It seems that there is an inability in the hybrid to 
reproduce to any extent the numerous hairs of the 5. flava type. 

Conducting Surface 

The conducting surface in these types reaches to the detentive 
surface without interruption. In 5. flava (PI. V, fig. 23) the 
cells were .07 mm. long, with a tip process .03 mm. in length. 
In 5. Drummondii (PI. V, fig. 25) the tip is longer, .05 mm. in 
length, while the whole cell measures .15 mm. In the hybrid 
(PI. V, fig. 26) the cell is .11 mm. long, with a tip intermediate 
in size, ,04 mm. The glands are grouped more abundantly 
over the upper conducting region, about the rim, and imme- 
diately below. Below this nectariferous area, the glands be- 
come less frequent and cease entirely over the lower half of 
the conducting surface. In 5. Drummondii there are 3-4 per 
field in this upper area; in S. Moorei, 4 or more. In 5. fluva, 
where the glands are not so limited in distribution, there are 
3 per field. 



22 Russell — Comparison of the Structure of Hybrid 

Longitudinal Section of the Rim 

A longitudinal section through the rim region of S. Drum- 
mondii shows that the rim is rolled over once as in 5. flava, 
but with no trace of the peculiar flattening on the under part 
of the turn. The tip is in S. Drummondii pointed and elong- 
ated, with thickened cells through the whole tip. The con- 
ducting cells do not appear until well around the outer curve 
of the rim ; while in S. flava they occur at the outermost edge 
of the rim. In S. Moorei they appear further around the rim 
than in 5. Drummondii. The tip region of S. Moorei is not 
so pointed as in 5'. Drummondii, nor as blunt as in S. flava; it 
is between the two. 

There are in S. Drummondii two rows of thickened cells 
subjacent to the conducting epidermis. S. flava has only one 
row of such cells, while in the hybrid there is a complete row, 
and a second incomplete row. 

The mesophyl of all three types is compact, excepting for 
the regions of the areolations in S. Drummondii and S. Moorei. 
Here the tissue is loose, with many air spaces. In S. Drum- 
mondii the cells of these areas are devoid of contents, but the 
tissue of this region is as deep as that of the non-etiolated por- 
tions. In 5. Moorei, in young leaves, these areas are not en- 
tirely devoid of chlorophyl, so that they appear light green 
rather than pure white as in S. Drummondii. 

Below the mesophyl there is in 5. Drummondii a reversed 
palisade of 3-4 layers of cells; in S. flava there are 3-4 layers; 
in 5. Moorei, 3 complete and regular layers. 

The outer epidermis of 5. Drummondii is swollen into peculiar 
pointed papillae. These become especially pronounced over 
the areolations. S. flava has a smooth epidermis, but in S. 
Moorei a trace of such swellings as are present in 5. Drummofidii 
occur. They are here more rounded than in 5. Drummondii. 

Detentive Surface 

On the outer part of the conducting and upper detentive 
areas of S. Drummondii there are stomata present. They are 
very sparsely scattered and rather difficult to find. About 
them is a group of special cells. In counting a hundred fields 
for detentive hairs, four such stomata were found. In S. Moorei, 



Sarracenias ivith that of Their Parents 23 

two stomata were found in a hundred fields. The number here 
is perhaps not to be taken as an average; but one may con- 
fidently assert that there are fewer stomata present in the hybrid 
than in S. Drummondii, although they may or may not be 
intermediate in number. 

The hairs of the detentive surface are about as numerous 
in S. Drummondii as in 5. flava, 5-6 per field. In 5. Moorei 
the hairs are more numerous — 7-8 per field. In length, as 
before, the hybrid is intermediate: 5. flava .37 mm. long, S. 
Drummondii .54 mm., 5. Moorei .45 mm. The epidermal 
cells from which they spring are straight walled cells, char- 
acteristic of detentive surfaces. 

Outer Epidermis of the Pitchers 

The epidermal cells of the outer surface of the pitcher tube 
are swollen as on the upper lid portion; excepting over the 
region of the veins, where straight walled, much thickened cells 
take their place. Stomata are very numerous, 10 or more to a 
field; glands are infrequent, one to a field; and hairs are absent. 
In S. Moorei the epidermal cells are slightly swollen; the stomata 
are more numerous than in S. Drummondii, 12 per field; glands 
are 1-2 per field; no hairs are present, as in 5. Drummondii. 

T. S. Tube at Base of Pitcher 

The cells of the outer epidermis of S. Drummondii are so 
swollen that the stomata appear sunken, instead of raised 
above the epidermal level as in 5. flava. There are here but 
three layers of false palisade. The mesophyl is deeper and 
looser than in 5. flava with peculiar bands of cells rich in con- 
tents forming a complete ring about the pitcher tube. There 
are two layers of sub-detentive cells, with tannin present. 

The tube sections of S. Moorei resemble those of S. Drum- 
mondii closely because of the presence here also of the peculiar 
bands of parenchyma cells in the mesophyl region. There are 
two layers of reversed palisade, and two rows of subdetentive 
cells with peculiar aggregated contents, noted above in S. flava. 

The "ridges" above the veins are more pronounced in 5. 
Drummondii than in 5. flava. S. Moorei shows an intermediate 
amount of thickening in this region. 



24 Russell — Comparison of the Structure of Hybrid 

Set J. S. Sledgei, S. Drummondii, and S. areolata 

S. Sledgei (PI. II, fig. 6) has an upright, slender pitcher, 
slightly inflated in its upper half, slightly constricted at the 
rim. Average pitchers are 55-65 cm. high. The pitcher of 
S. Drummondii (PI. I, fig. 4), it will be remembered, increased 
gradually in width, up to the rim. S. areolata (PI. II, fig. 7) 
is about as high as S. Sledgei — 55-65 cm. The rim is not con- 
stricted as in 5. Sledgei, nor is it so expanded as in 5. Drum- 
mondii. The fused lamina extends but little in these three 
forms. It is about 4 mm. wide in S. Sledgei, while in S. Drum- 
mondii it is very narrow — only 2 mm. wide. S. areolata shows 
it about as in S. Drummondii, or slightly wider. 

The lid in S. Sledgei is ovate- cord ate, with a straight margin. 
In its median portion it is prolonged into a tip. S. areolata 
shows a lid intermediate in shape between the ovate lid of 
5. Sledgei, and the orbicular frilled lid of S. Drummondii. There 
is a slight tip process. 

The pitchers of S. Sledgei are green, veined with crimson 
over the upper portion and the lid region. There is also a 
ruddy variety with deep crimson lid and upper tube. 5. Drum- 
mondii, of the type described as one of the parents of S. Moorei, 
has a green pitcher marked on the lid and upper tube with 
white areolations and reddish veinings. S. areolata has more 
pronounced reddish purple vein markings than 6". Drummondii. 
The white areolations are reproduced over the upper lid and 
pitcher areas, but are fainter than in 5. Drummondii. Where 
the 5. Drummondii parent is of the atropurpurea type, the 
hybrid is very richly colored with purple lid and white mark- 
ings. 

Outer Lid Surface 

In S. Sledgei (PI. Ill, fig. 13) the epidermal cells are longer 
than broad, with angular walls. There are numerous stoma ta 
distributed equally over the epidermal surface, averaging six 
to a field. Glands are sparse — one to a field on this outer sur- 
face. There are but few hairs, and these are extremely short. 
In S. Drummondii (PI. Ill, fig. 11) the cells are rounded, swollen; 
glands and stomata are distributed in limited areas between 
the areolations. In the hybrid (PI. Ill, fig. 14) the epidermal 
cells are inclined to have rounded walls, slightly swollen into 



Sarracenias with that of Their Parents 25 

papillae. The stomata and glands are grouped in special tracts 
as in 5. Drummondii, but they are wider and less well defined. 
There are strong hairs scattered abundantly over the lid sur- 
face, especially around the margins of the window areas. They 
are much stronger than in either parent. 

Inner Lid Surface 

The epidermal cells of the inner lid surface of S. Sledgei (PI. IV, 
fig. 20) are longer than broad, and wavy-walled. In S. Drum- 
mondii (PI. IV, fig. 18) they are about as long as broad, with 
walls slightly wavy. 5. areolata (PI. IV, fig. 21) has cells re- 
markably intermediate in size and shape. 

Stomata are sparsely distributed over the inner lid region 
of S. Drummondii, where the average per field is .59. In 5. 
Sledgei they are quite abundant — 3-4 per field. In the hybrid 
they are quite intermediate in number — 2-3 per field. 

The hairs of the lid in 5. Drummondii are variable in length. 
They exceed in their greatest length the hairs of S. purpurea, 
reaching almost 2 mm. in length, while the shorter ones are 
only .3 mm. long. 

In S. Sledgei on the other hand the hairs are of a uniform 
length. They are stout and short, \'arying slightly from .55 
to .88 mm. long. None are as short as the shorter of those of 
S. Drummondii, .3 mm. In 6". areolata the hairs vary greatly 
in length after the fashion of the 5. Drummondii parent. There 
are hairs present as short as the shortest of S. Drummondii, 
but the longest hairs are a little over half as long as the longest 
hairs of S. Drummondii — i mm. Hairs .y-.Q mm. in length 
are the most numerous. That is the influence of the S. Drum- 
mondii parent is shown in the tendency to wide variation in 
length, and in the lengthening of all of the hairs. The glands 
in the three forms are fairly numerous — 4 in S. Drummondii, 
4 in S. Sledgei, and 4 in 5. areolata. 

Conducting Surface 
Conducting surface cells here do not show the exact relation 
shown in the other hybrid. In S. Drummondii (PI, V, fig. 25) 
the cells were large and measured .15 mm. in length. In S. 
Sledgei (PI. V, fig. 27) the cells are about .09 mm. long, and are 
narrow and oval in shape. In S. areolata (PI. V, fig. 28) the 
cells are of the same length as in S. Sledgei, but are wider and 
in shape are halfway between the parent forms. 



26 Russell — Comparison of the Structure of Hybrid 

The glands in these three forms are most numerous about 
the pitcher rim, and quickly lessen in number one inch or so 
below the rim. They are scattered sparsely for a short space 
below, but cease entirely beyond the upper one-third of the 
conducting surface. In S. Sledgei the glands are remarkably 
numerous, 7-8 per field over the upper region, near the rim. 
In 6". Drummondii they are more infrequent and average 3-4 
per field. In the hybrid there are almost as many as in S. 
Sledgei — 6-7 per field. In the extreme lower portion of the 
conducting surface in all three forms are stomata scattered 
very sparsely, set in a group of special cells. 

Longitudinal Sections of the Rims 
The rim of S. Sledgei is rolled over once in a rather loose 
turn. The tip is blunt with several thickened cells. The 
conducting cells appear about halfway round the outward turn. 
Beneath the conducting cells is a single layer of subepidermal 
cells. The mesophyl is deep and loose. There are two layers 
of cells forming a false palisade below the epidermis. 

In 5. Drummondii there are two sub-conducting and 3-4 sub- 
epidermal layers. The mesophyl is loose, especially below the 
areolations. 

In S. areolata the rim is intermediate. Beneath the con- 
ducting cells are two layers of subepidermal cells. The meso- 
phyl is deep and loose especially below the window areas. Be- 
neath the outer epidermis are three subepidermal palisade 
layers. 

Detentive Surface 

The detentive surface of S. Drummondii is, as has been de- 
scribed above, composed of normal straight-walled polygonal 
epidermal cells. A few normal stomata are scattered over this 
surface, but no glands are present. Hairs are present, of the 
normal variety, .8-.9 mm. long, 3-4 to a field. 

In 5. Sledgei this surface departs from the normal detentive 
in that some of its cells are wavy walled, with very different 
contents from those of the detentive epidermal cells. These 
cells appear only on the upper detentive area in large groups 
isolated in the midst of characteristic detentive cells. Other 
cells show all transitions between straight walled detentive 
surface cells, and isodiametric wavy walled cells resembling 



Sarracenias ivith that of Their Parents 27 

closely the glandular surface cells of 5. purpurea. In fact the 
whole area has much the same character as the corresponding 
area in the hybrid 6". Catesbaei, excepting that none of these 
cells appear as intrusions among the conducting surface cells, 
and that they extend deep into the detentive surface. The 
writer infers the probability that this region represents a primi- 
tive glandular surface. 

On the normal detentive surface the hairs are short, .3-.4 
mm. in length, but numerous, 7-8 per field. The hybrid pos- 
sesses a normal detentive surface with polygonal cells and no 
glands. Stomata are present. The hairs are intermediate in 
size and number. They are .6-. 7 mm. long, with 5-6 per field. 

Transverse Sections of Tube 

5. Drummondii, as has been previously noted, shows in trans- 
verse sections of the tube-base epidermal cells swollen into 
papillae; below these, two subepidermal layers, a loose mesophyl, 
and 1-2 subdetentive layers occur. 

In S. Sledgei the epidermal cells are oval. Below them are 
three layers of subepidermal cells. The mesophyl is loose with 
many air spaces. The mesophyl cells contain the same peculiar 
contents noted in the section of S. Drummondii. In this form 
however the cells so supplied are arranged in a continuous 
layer in the mesophyl tissue, below the false palisade tissue. 
There are 1-2 layers of sub-detentive cells. 

In S. areolata there are two layers of subepidermal cells; 
and two layers of sub-detentive cells. The mesophyll is loose 
as in both parents. There is a suggestion of the peculiar bands 
of special storage cells, as in the case of S. Sledgei, though the 
layers are not continuous. 

Flowers 
S. flava, S. purpurea, S. Catesbaei 

The flower of 5. flava is pendulous and measures 7 cm. in 
length, 13 cm. across. Those of S. piirpurea are smaller, 4-5 
cm. long and 9 cm. wide. In specimens at hand of 5. Catesbaei 
the flowers are intermediate in size, 5-6 cm. long and 10-12 
cm. wide. Other specimens seem to point to a greater robust- 
ness in it than in either parent. 

The bracts in all three are small, covered with honey glands 
and a few stomata. The glands are distributed over the central 



28 



Russell—Comparison of the Structure of Hybrid 



part. In color, in 5. fiava they are yellowish membranous, 
with green veinings. Those of S. purpurea are reddish, or 
green with a reddish margin. In S. Cateshaei the bracts are 
reddish with a green tip. 

The sepals of S. jiava are 4 cm. long by 3 cm. broad. They 
are ovate and greenish yellow. Stomata are frequent, and the 
numerous glands are massed towards the edges and tip of the 
sepals on the outer side. On the inner, or morphologically 
upper, surface the glands and stomata are less frequent than 
on the outer side, but distributed in the same manner. 

In S. purpurea the sepals are 3 cm. long, ovate as in S. fiava 
and red in color. Glands are not so numerous as in S. fiava, 
but distributed along the margins as above. The sepals of 
5. Cateshaei are 4 cm. long, ovate, green tinged with rosy pink, 
or with red veinings. Glands and stomata are more numerous 
than in S. purpurea, distributed as before. 

The petals in S. fiava are 7-8 cm. long, with the proximal 
portion not wider than the distal expanded part. The expanded 
portion at its lower third forms a cuneate tip characteristic of 
S. fiava. In color the whole petal is a flavous yellow, the pig- 
ment being due to yellow chromoplasts. The constricted por- 




Fig. 29. Outline drawings of petals of Sarracenia flowers X }4. See text 

for description. 

tion of the petal (fig. 29, b) is rolled over rather deeply. Glands 
and infrequent stomata are distributed alightly behind the 
tip of the petal, and along several of the median veins. At 
the region of the constriction they become very numerous. 
In this area too, the epidermal cells become swollen into rounded 



Sarracenias with that of Their Parents 29 

papillae. Above the constricted area there are no stomata, 
nor glands, nor papillate swellings. On the inner surface, the 
distribution of stomata and glands is practically as above, 
excepting for the presence of several rather long, fine hairs 
along the median veins of the constricted area. S. purpurea 
has petals 4-5 cm. long. The proximal portion of the petal is 
not wider than the distal section. The constriction between 
them is very shallow (fig. 29, a), and the sides of the petals 
scarcely rolled back. The distal portion of the petal is ovate. 
In color, the petal is crimson without, much lighter within. 
The base of the petal is pale greenish or whitish. Glands are 
numerous over the central part of the petal, back as far as the 
constriction. In 5. Catesbaei the petals are intermediate in 
length, 5-6 cm. long. The upper portion is slightly more 
rounded than in 5. purpurea; the constriction is more pro- 
nounced than in the latter (fig. 29, c). The color is inter- 
mediate. Above, the petal is white. The lower portion of 
the petal is rose-pink. That is, the purple-pink dissolved 
pigment in S. purpurea is diluted and weakened by the chromo- 
plasts from 5. flava. Glands are present at the tip, and along 
the median veins only to the constricted areas. 

The stamens in all are variable in number — from 50-60. 
They are formed by the breaking up of each of the 10 staminal 
primordia into 5-8 lesser primordia. 

Pistil. The umbrelloid style is provided with numerous long 
hairs, pointing generally toward the 5 stigmatic knobs. The 
stigmatic hairs are short and stout, usually bent with the tip 
often swollen. 

In 5. flava, the stigmatic hairs are short and but slightly 
curved, with swollen tip. 

In S. purpurea, the hairs are longer, and more decidedly 
curved. The hairs of S. Catesbaei are longer than those of 
5. flava, yet not so long as those of 5. purpurea. The stylar 
hairs are abundant and long in 5. flava. In S. purpiirea the 
hairs are of about the same length, sparse within, absent with- 
out. In S. Catesbaei, however, the hairs are very short. 

S. flava, S. Drummondii, S. Moorei 

In 5. Drummondii, the flowers are pendulous, as in 5. flAiva, 
are of about the same size, 6-7 cm. long, and 14 cm. across their 
greatest width. The bracts are red. 5. Moorei has usually. 



30 Russell — Comparison of the Structure of Hybrid 

at least in all the greenhouse specimens, a larger flower than 
those of the parents. They are 7 cm. long and 13-15 cm. across. 
The bracts are reddish green. 

The sepals are deep crimson in 5. Drummondii, ovate in 
shape, measuring 4-5 cm. in length. Those of S. Moorei are 
of like size, but show an intermediate coloring and shape. They 
are reddish pink above, and yellow beneath, and are rather 
narrower than the sepals of S. flava (35). Stomata and glands 
appear as before at the tip and along the sides of the sepals. 

The petals are interesting in relation in this series. They 
are 6-7 cm. long in S. Drummondii (fig. 29, d) and have a basal 
segment which is rhomboidal in shape, and much wider than 
the "banner" below. The margin of the petal is rolled back 
strongly at the constriction ; the banner portion is oval in shape 
and the whole petal is colored a rich deep crimson, due to a 
dissolved crimson pigment, except at the extreme base, where 
the petal is green. The epidermis of the petal, like the outer 
epidermis of the pitcher, is swollen into papillae, which become 
especially prominent in the constricted area. There are few 
glands scattered at the lower part of the petal, and up the me- 
dian veins. There are none in the constricted area of the petal, 
where they are so numerous in S. flava. 

In S. Moorei (fig. 29, e) the petals are intermediate in color 
and shape. The basal portion is wider than in 5. flava and nar- 
rower than in 5". Drummondii. The lower portion of the petal 
is pointed, somewhat suggesting the cuneate tip of 5. flava, but 
rounds out above more like S. Drummoyidii. In color the 
petals are light at the base — a yellowish green, becoming a 
peculiar maroon color below the base on the outer side of the 
petal and yellow within, due to combined crimson dissolved 
pigment and yellow chromoplasts of S. Drummondii with the 
yellow chromoplasts of S. flava. The glands are less numerous 
than in S. flava, but are distributed in the same way, toward the 
tip, up the median veins and over the constricted area. 

In S. Drummondii, the style is flushed with crimson over 
its outer surface; while in 5. flava it is yellow. In 5. Moorei 
the style is yellowish, with faint red markings. 

The hairs of the umbrelloid style of 5. Moorei are longer and 
stronger than those of the parents. 



Sarracenias ivith that of Their Parents 31 

5. Drummondii, S. Sledgei, and S. areolata 

The flowers of 5. Sledgei are nodding, but the petals are 
spreading in this form, instead of drooping and hanging out as 
banners, as in the other types so far considered. They are 
rather large and showy, 5-7 cm. long, 11-14 cm. wide. Those 
of 5. areolata exhibit somewhat the same spreading habit as in 
S. Sledgei. The flowers are 5.5-6 cm. long, 13 cm. across. 

The bracts in S. Sledgei are pink with a greenish tip; those 
of 5. areolata more red, due to the 5. Drummondii parent. 

The sepals of 5. Sledgei are greenish, fading to yellow. They 
are ovate with blunt tips and measure 3-4 cm. long. Those 
of the hybrid are longer, 4-5 cm., and are cordate in shape. 
They are greenish with a red margin. Glands are present on 
the tip and along the margins of the sepals. 

The petals of 5. Sledgei (fig. 29, f) are about 6 cm. long, with 
a wide basal segment, a deep constriction, and a much rounded 
"banner." They are pale lemon-yellow in color, fading to 
white. Glands are very sparsely distributed, one or two at 
the tip and several up the central vein. They do not appear 
above the constriction. As before, the cells of this portion of 
the petal, on the outer surface, are swollen into slight rounded 
papillae. 

In S. areolata (fig. 29, g) the petals resemble S. Sledgei in 
that the shape of the banner is decidedly rounded. The basal 
portion is wider than in S. Sledgei, approaching to rhomboidal 
as in S. Drummondii. In color they are intermediate between 
the crimson of 6*. Drummondii and the yellow of S. Sledgei. 
The color is rather more rose-pink than red on the outer surface, 
while within the petals are pale yellow. There are no glands 
present on the petals, at the constriction. The epidermal cells 
are prominently papillate, though not so strongly as in 5. Drum- 
mondii. 

The umbrelloid style is pale yellow in S. Sledgei, while in .S". 
areolata it is more greenish in color, with red veining. 

The hairs of the inner side of the style are short, while in 
S. areolata they are remarkably long and strong, exceeding even 
those of S. Drummondii. The hairs of the stigma of S. Sledgei 
are short and curved, while those of the hybrid are longer and 
much less curved. 



32 Russell — Comparison of the Structure of Hybrid 

Glands 

The structure of the glands on the pitcher surfaces, spoken 
of in this paper, is in general identical. Brief descriptions 
have been given, and several figures by Goebel (32), Fenner 
(31), and others. There are above, appearing on the epidermal 
surface, two central cells, heavily thickened, surrounded by 
from 4 to 6 companion cells. The cap cells, or the central 
cells, are wedge-shaped, and run down between the surrounding 
cells into the second or third tier of cells constituting the gland. 
The whole structure is then flask-shaped, and is composed of 
16 or more cells, extending down into the mesophyl, but sep- 
arated from that tissue by a cuticular lamella, with reticulate 
thickenings. The cap cells mentioned above stain differently 
from the surrounding cells, taking gentian-violet stain deeply, 
while the surrounding cells absorb safranin. Further, the 
surrounding cells give a marked positive reaction for tannin, 
with ferric iron chloride. In view of the above, it seems very 
probable that the cap cells are the secretory cells, and that the 
tannin present is the source for the sugar in the secreted liquid. 

Though the structure of these glands has been considered 
briefly, there has been but one paper tracing their develop- 
ment — that of Fenner (31). He describes their origin from 
an epidermal initial cell which divides longitudinally and trans- 
versely to form a two-tiered group of cells. But next he con- 
siders that a split occurs between the upper cells, and that this 
split deepens until it involves the lower layer also. Into this 
"pit," he says, the secreted honey is poured. The writer finds 
no evidence of any such splitting. In fact the pit he mentions 
occupies the position of the cap cells. What occurs is this: 
The gland initial divides longitudinally and transversely as 
indicated, forming a two-tiered structure of four cells, two 
above, two below. From the two upper cells are cut off two 
smaller cells after the fashion of guard cells. These two cells 
are the cap cells. The two upper cells redivide to form the 
4-6 surrounding cells. The second tier below divides trans- 
versely and longitudinally into 8-16 cells to form the second 
and third tiers. While this growth is going on, the two cap 
cells are pushed to a central position, and are flattened against 
each other until they assume the characteristic wedge shape (32). 



Sarracenias with that of Their Parents 33 

Ovarian Gland Structure 

The above description applies to the glands present on all 
the vegetative parts, as well as on the bract, sepals, the petals 
and umbrelloid style. But over the tubercles on the surface of 
the ovary are still more complex glands. Macfarlane (28) 
gives the following description of the nectar secretion: "The 
epidermal cells of the ovarian surface have undergone repeated 
divisions, and have swollen out into minute glassy beads or 
tubercles from which a quantity of rich nectar exudes before, 
during, and for some time after, blossoming. This, as we will 
show, is evidently of great use in the pollination of the flower." 
"When a flower has nearly opened the stamens begin to dehisce 
and as the blossom has a pendulous position the pollen from the 
stamens is showered down into the umbrelloid style-cavity below. 
But about this time the warted bead-like ovarian surface exudes 
large drops of sweet juice, which increases in quantity as the 
stamens continue to dehisce, till it oozes down among the fila- 
ments and anthers, washing with it the pollen-grains. It then 
accumulates in the umbrelloid cavity, and forms there a nectar- 
bath of pollen." 

When serial sections of the ovarian wall of an opened flower 
are studied, the source of the abundant honey is seen to be in 
the large nectar glands situated at the bases, and along the 
sides, of the tubercles mentioned above by Macfarlane. The 
glands are more numerous over the tubercles of the lower half 
of the ovary. The tubercles over the upper surface of the ovary 
are devoid of glands. Following is an account of the mode of 
origin of the tubercles and glands: 

In a very young flower, where the anthers show the pollen 
mother cell stage, the ovary is as yet very small, and its epi- 
dermis smooth. The ovarian tissue is, however, growing rapidly 
at this period, and division figures are frequent. They indicate 
a longitudinal division for the epidermal cells invariably, while 
in the subjacent tissue both longitudinal and transverse 
divisions are common. At this time both petals and sepals 
possess fully formed glands and stomata. The ovarian wall as 
yet shows no trace of either. The epidermis continues to 
divide more frequently than the tissue below. This excessive 
division is somewhat localized along the ovarian wall, so that 
there results here and there a slight swelling. The layer im- 



34 '^ Russell — Comparison of the Structure of Hybrid 

mediately below the epidermis becomes differentiated also from 
the ovarian tissue. The cells become enlarged and filled with a 
peculiar content present in the epidermis also. This layer 
shows rapid division and pushes up into the swelling. It is 
impossible at this time to trace the gland initial cell. At this 
time, the pollen mother cells are in the anaphase of the first 
or heterotypic division. 

As the epidermal cells divide, the swellings become more 
pronounced. Two subepidermal layers become involved. The 
outer cells of the tubercles become enlarged and oblong while 
the cells between the swellings become compressed and small. 
The first gland initials are found at this stage. They are usually 
situated at the base of the swellings and consist of one or two 
cells with a large nucleus and richly granular protoplasm. At 
this time the pollen grains are in the tetrad stage, and the mega- 
spore mother cell is distinguishable. 

The swellings become deepened as the flower matures and 
press together tightly so that they assume a squarish or oblong 
shape (fig. 30). At this time the glands are fully developed. 




Fig. 30. Longitudinal section through mature ovarian wall, X lOO. G = 
gland in section; E= epidermis with waxy layer on outer surface. 

They have the same fundamental structure as the simpler 
glands on the leaves, etc.; that is, they possess a set of 2 or 
frequently 3-4 central cells running down into a mass of small 
cells below. 

The gland is irregularly spherical in shape, and is composed 
of many more cells than the glands on the pitchers. There 
may be 60-80 cells concerned in the formation of the ovarian 



Sarracenias with that of Their Parents 35 

glands. They lie embedded in the tissue of the papillae, for 
the most part at their base. The honey secretions are poured 
out into the tiny crevasses between the papillae, and are drawn 
upwards by capillarity to the lower part of the ovary, there 
to collect about the base of the filaments as has been noted by 
Macfarlane above. 

The papillae, mentioned as being nectariferous (28) in them- 
selves, are oblong masses of fundamental tissue. The outer- 
most or epidermal layer and a subepidermal layer become en- 
larged, and regular, forming a noticeable bounding layer. These 
two outer layers contain a peculiar substance from the earliest 
stages of their differentiation. They have on their outer sur- 
face a coating of wax which gives with alkanna and Soudan III 
a characteristic reaction. The tissue of the papillae is richly 
supplied with oil globules. The contents of the cells of the 
bounding layers stain deep brown with iodine and potassium 
iodide, indicating perhaps that an alkaloid is present. Its 
position and abundance may indicate the presence of such a 
protective substance. An alkaloid has been mentioned as being 
present in the family by Porcher (34). Sarracenin was the 
name temporarily applied to it, and it was thought to have 
medicinal value for stomach troubles and smallpox. Such an 
alkaloid, however, is not mentioned in such a treatise as that of 
Winterstein and Grier. Several diagnostic tests for alkaloids 
were applied besides iodine in potassium iodide. Nitric acid 
on sections dampened with potassium hydroxide in alcohol 
gave a rather deep orange color, with here and there a decided 
pink tint in the bounding layers. No reaction occurred with 
platinic chloride. On adding ammonia, a decided bright green 
color was obtained. 

In view of the fact that these papillae have their outer walls 
heavily thickened and covered with a protective waxy coating; 
and are supplied with abundant nectariferous glands over the 
lower portion, it is evident that the nectar is secreted by the 
glands and not by the papillae as a whole. 

Conclusions 

It will be seen from the above description that the hybrid 
forms, in comparison with their parents, are intermediate in 
relation in almost all details. 



36 Rttssell — Comparison of the Structure of Hybrid 

In size it has been shown that the hybrids are generally inter- 
mediate, though S. Moorei and 5. areolata frequently incline 
to show a characteristic increase in vigor over the parent types. 

In shape the intermediateness is particularly well shown in 
the first hybrid, 5. Catesbaei (fig. 3), where the diverse shapes 
and habits of the two parents are so neatly blended. The 
parents of the other forms do not present so diverse an appear- 
ance; but in small details, such as the shape of the mouth open- 
ing, or the width of the fused laminae, the hybrid shows an 
intermediate character. 

In all the blending of the parental lid shapes is shown. Where 
a form with a frilled margin — as in 5". Drummondii or 5. pur- 
purea — is crossed with a form with a straight margin, the result- 
ing hybrid has a lid with a frilled margin, but more loosely 
wavy than in the parent. When a form like S. flava, which 
has a median tip process on the lid, is crossed with a blunt 
tipped form like 5. purpurea, the resulting hybrid has a tip, 
but much weaker than that present in S. flava. 

In the matter of coloring, the blending is beautifully shown. 
If a form with red markings be combined with a green form 
showing no such markings, the hybrid will have the markings 
reproduced at half the intensity of the parent. 

The flowers, in the matter of their size and shape, show a 
marked blending, though here too the hybrid is inclined to 
be larger and more showy than either parent. 

A remarkable series is shown in the comparative petal shape 
and size. The figures given show how intermediate the hybrid 
is in relation. 

In odor also the hybrid blends the parental characters — 
for instance, S. flava has a very decided and unpleasant odor, 
while S. Drummondii has a rather delicate sweet scent. Their 
hybrid has a stronger odor than 5. Drummondii, but not at all 
unpleasant. 

The intermediate relation in the matter of flow^er coloring 
in the three sets has been noted. Quite noticeable is the pecu- 
liar maroon color obtained in the hybrids with 5. Drummondii 
as a parent. 

All of these examples of blending parental characters seen 
in the hybrids are such as any one can note with the naked eye. 
The intermediate relation is, however, much more intimate and 



Sarracenias with that of Their Parents 37 

exact. It extends to microscopic details in structure to be 
noted below. 

The epidermal cells of the outer surface of the pitcher and 
of the inner lid surface show a blended appearance in the 
hybrid. Take for example S. Moorei (fig. 12), whose cells are 
intermediate between the rounded epidermal cells of 6'. Driim- 
mondii (fig. 11) with their pronounced papulation ; and the 
wavy walled cells, without papillae, of S. flava (fig. 9). 

The epidermal cells of the conducting surface of the hybrids 
are remarkably intermediate between the parents. Here there 
are measurable differences in length of cell and tip of process, 
and it has been shown that the hybrid lies exactly between the 
parents in length relation, breadth, and tip length. 

On the outer and inner surfaces where stomata are present, 
the hybrid shows the number present in a given field to be an 
exact arithmetical mean between the numbers present in the 
parents. In regard to their distribution it has been noted that 
in other species the stomata are equally distributed over the 
surface, while in S. Drummondii they are limited to special 
tracts between the window areas. The hybrids with 5. Drum- 
mondii show the stomata distributed in wide tracts (figs. 12, 14). 

The unicellular hairs distributed over the various surfaces 
show several interesting relations. 

On the detentive surface, the hybrid presents an arithmetical 
mean between the parent types in number and length of hair in 
each set. Over the outer surface of the pitcher, where the 
hairs are irregularly scattered, the relation is somewhat ob- 
scured. But in S. flava (fig. 9), S. Catesbaei (fig. 10), 5. ptir- 
purea (fig. 8) one may see how the hybrid shows a variety of 
hair lengths inherited, and an intermediate degree of blending 
in the hairs. 

On the inner lid surface, the hairs of all except two species 
show great variability in length. The hybrids with either of 
these two forms S. flava and S. Sledgei as a parent, having fairly 
uniform hairs, with any of the other forms, having variable 
lengths, show hairs of all lengths reproduced, but fewer in 
number and with the longest hairs much reduced. 

This behavior of hair-length inheritance has been noted be- 
fore in other plants (29) so that this seems to be a rule of inheri- 
tance for hair length and number. 



38 Russell — Comparison of the Structure of Hybrid 

In relation to the actual structure of the pitcher, longitudinal 
sections of the rim have been compared. It has been noted 
that, in the rolling, in the shape of the tip, in the amount of 
thickening at the tip, the hybrid is intermediate in character. 

In all transverse and longitudinal sections of the pitcher, 
the number of layers of false palisade, of subepidermal cells, 
and the depth and character of the mesophyll, have all indi- 
cated an intermediate relation in the hybrid. 

In the amount of thickening, either in sclerenchymatous 
tissue about bundles, or in the number of striations on the 
hairs of the inner lid surface, the hybrid is invariably inter- 
mediate. 

Bisexual Hybridity 

Some apparent variations from the exact blending should be 
noted here. On pages i6 and 17 there is an account of the 
inability of the glandular surface of S. purpurea to blend with 
the conducting surface of S. flava. The resulting mosaic effect 
is described. This obtains also in the hybrid of S. purpurea 
with 5. Drummondii, and has been noted in the hybrid with 
6". minor. The inability is probably due to the fact that 5". 
purpurea has evolved far in advance of all other forms, except 
possibly S. Sledgei. It would be interesting to know if of all 
the forms this could perfectly blend with S. purpurea when 
crossed. Unfortunately such a hybrid has not been found. 

In the hybrid of S. Sledgei with S. Drummondii, the develop- 
ing glandular area is completely lacking; the impulse is too 
weak for transmission. 

Other peculiarities of relation in parent and hybrid types 
might be illustrated by the relation shown in comparisons of 
counts obtained for glands. In every case practically the 
hybrid shows fewer glands than either parent. It is almost 
impossible to obtain a hundred or more counts from a given 
surface, and compare it with a hundred similar counts from 
exactly corresponding surfaces. The glands are grouped in 
S. flava for instance around the rim, and down the median 
back portion of the pitcher. They extend halfway down the 
length. In 5. Drummondii they are massed about the rim 
too, but are very sparse just below. If the total number of 
glands could be counted and compared, they would undoubt- 



Sarracenias with that of Their Parents 39 

ediy show a perfectly exact relation. This is upheld by the 
fact that where a surface without glands (in 5. flava) is crossed 
with a surface where the gland number is uniform (glandular 
of S. purpurea) the hybrid shows an exactly intermediate num- 
ber. In the case too where they are massed in the same regions 
in parents and hybrids, as in S. Sledgei, S. Drummondii, and 
5. areolata, the hybrid shows a blended relation. 

The comparison of these three hybrid plants with their parents 
in all details of structure gives an overwhelming mass of evi- 
dence for exact blending, which extends to the most minute 
details. It surely points to some exact relation in molecular 
structure of the hybrid plant, extending even to the amount 
of thickening laid down in a cell wall, the size of the starch 
grains, or the size of a chloroplast. 

The writer wishes to acknowledge the kindness and coopera- 
tion of Dr. J. M. Macfarlane in the preparation of this paper. 
Thanks also are due to Mr. W. R. Taylor, who made many 
of the microphotographs; and, through the kindness of Mr. 
Frank M. Jones, the writer was able to examine fresh flowers, 
which he sent from Alabama, Mississippi, and Florida. 



BIBLIOGRAPHY 

1. Tournefort, J. T. Institutione Rei Herbariae, 3rd Ed. (1719). 

2. Linnaeus, C. Species Plantarum, ist Ed. (1753). 

3. Clusius, C. Rariorum Plantarum Historia (1601). 

4. Parkinson, John. Theatrum Botanicum (1640). 

5. Josselyn, New England Rarities Discovered (1672). 

6. Plukenet, L. Phytographia, Part III, Tab. 152 (1692). 

7. Plukenet, L. Amaltheum, Tab. 376 (1705). 

8. Ray, John. Historia Plantarum, Vol. II (1688). 

9. Walter, Thos. Flora Caroliniana (1788). 

10. Bartram, Wm. Travels (1791). 

11. Michaux, Andre Flora Boreali America (1803). 

12. Croom, H. B. Catalogue of Plants (1737). 

13. Anonymous. Flore des Serres (185 1). 

14. Chapman, A. W. Flora of the Southern United States (i860). 

15. Hooker, W. J. Gardeners' Chronicle, Vol. IX, p. 260 (1874). 

16. Boulger, Prof. Gardeners' Chronicle, Vol. XV, p. 627 (1881). 

17. Macfarlane, J. M. Roy. Hort. Soc. Conf. Genetics, p. 155 (1906). 

18. Masters, M. T. Gardeners' Chronicle, Vol. XV, p. 816. Vol. XVI, 

p. II, 40 (1881). 

19. de Candolle, A. Prodromus, Vol. XVII (1870). 



40 



Russell — Comparison of the Structure of Hybrid 



20. Nicholson, George. 

21. Moore, David. 

22. Veitch & Son. 

23. Macfarlane, J. M. 

24. Macfarlane, J. M. 

25. Bailey, L. H. 

26. Elliot, Stephen. 

27. Eaton, Amos. 

28. Macfarlane, J. M. 

29. Macfarlane, J. M. 

30. Solereder, Hans. 

31. Fenner, C. A. 

32. Goebel, K. 

33. Harper, R. M. 

34. Harper, R. M. 

35. Mohr, C. 

36. Shreve, F. 

37. Porcher, F. P. 

38. Walter, Herbert E. 



Dictionary of Gardening, V^ol. HI. 

Gardeners' Chronicle, Vol. XXH, p. 702 (N. S.) 

(1874). 
Gardeners' Chronicle, Vol. XXHI, p. 738 (1874). 
Pflanzenreich IV, no (1906). 
Contrib. Bot. Lab., Vol. II, p. 426 (1904). 
Encyclop. Horticulture, Vol. VI (1917). 
Botany of South Carolina and Georgia (1821). 
Manual of Botany (1833). 
Annals of Botany, Vol. VII, p. 445 (1893). 
Trans. Roy. Hort. Soc, Vol. 37 (1892). 
Anatomy of the Dicotyledons, Vol. I, p. 51 (1908). 
Flora, Vol. 93, p. 351 (1904). 
Pflanzenbiologischen Schilderungen, Vol. 2, p. 89 

(1893). 
Jour. Elisha Mitchell Scientific Soc, Vol 39, No. 3 

(1918). 
Bull. Torrey Bot. Club, Vol. 34, p. 351 (1907). 
Bull. Torrey Bot. Club, Vol. 24, p. 23 (1897). 
Bot. Gazette, Vol. 42, p. 107 (1906). 
Resources of the Southern Fields and Forests 

(1869). 
Genetics, An Introduction to the Study of Heredity, 

p. 12 (1913)- 



EXPLANATION OF PLATES 



Plate I. 




Fig. 1. 


S. purpurea. 


Fig. 2. 


S. fiava. 


Fig. 3- 


S. Catesbaei. 


Fig. 4. 


S. Drummondii. 


Plate II 




Fig. 5- 


S. Moorei. 


Fig. 6. 


S. Sledgei. 


Fig. 7- 


S. areolata. 



(The above photographs were made by W. R. Taylor from specimens in the 
Sarracenia House at the Univ. of Penna. Bot. Gardens.) 



Plate HI. Micro-photographs of outer epidermis of lids of pitchers X 70. 
Fig. 8. 5. purpjirea. 
Fig. 9. 5. flava. 
Fig. 10. 5. Catesbaei. 
Fig. II. 5. Drummondii, 



Sarracenias with that of Their Parents 41 

Fig. 12. 5. Moorei. 
Fig 13. S. Sledgei. 
Fig. 14. 5. areolata. 

Plate IV. Micro-photographs of the inner epidermis of lids of pitchers X 50. 

Fig. 15. 5. purpurea. 

Fig. 16. S. flava. 

Fig. 17. 5. Cateshaei. 

Fig. 18. 5. Drummondii. 

Fig. 19. S. Moorei. 

Fig. 20. S. Sledgei. 

Fig. 21. 5. areolata. 

(Photographs by W. R. Taylor.) 

Pl.\te V. Micro-photographs of epidermal cells of the conducting surface 
X 500. 

Fig. 22. 5. ptirpurea. 

Fig. 23. 5. flava. 

Fig. 24. 5. Catesbaei. 

Fig. 25. S. Drummondii. 

Fig. 26. 5. Moorei. 

Fig. 27. 5. Sledgei. 

Fig. 28. 5. areolata. 

(Photographs by W. R. Taylor.) 



A Comparative Study of the Structure and 

Saprophytism of the Pyrolaceae and 

Monotropaceae with Reference 

to their Derivation from 

the Ericaceae 



Margaret W. Henderson, B.S., M.A. 

[Thesis presented to the Faculty of the Graduate School in partial fulfillment of the 
Requirements for the Degree of Doctor of Philosophy.] 



CONTENTS 



PAGE 

Introduction 43 

Historical 48 

Methods and Materials Used 50 

The Underground Root and Stem Systems 51 

The Root 53 

The Rhizome 64 

The Ascending Axis 64 

The Leaf 75 

The Leaf — Microscopic Structure 78 

The Inflorescence 87 

The Sepals 90 

The Petals 92 

The Stamens 94 

The Pistil 97 

The Fruit and Seed 10 1 

Summary 103 

Conclusions 105 

Bibliography 106 

42 



Introduction 

In the families of flowering plants which show saprophytism 
and parasitism there occur usually green purely autophytic 
plants with typical green leaves and numerous flowers; plants 
that are purely saprophytic or parasitic, with colorless scales 
and a reduced number of flowers; and all gradations between. 
In a comparative study of such typical families showing sapro- 
phytism, i.e., the Burmanniaceae, Orchidaceae, Gentianaceae, 
and Ericaceae, and those showing parasitism, the Loranthaceae, 
Santalaceae, Balanophoraceae, Rafflesiaceae, Lauraceae, Con- 
volvulaceae, and Scrophulariaceae, one notices a common ten- 
dency in the saprophytic or parasitic members toward condensa- 
tion and simplification as the saprophytism or parasitism be- 
comes more pronounced. To illustrate from the parasitic group, 
in the Loranthaceae the genera Nuytsia and Gaiadendron are 
upright independent trees; the genus Loranthus consists of 
upright shrubs with large leaves and numerous flowers as L. 
Baroni Baker and L. pulcher D.C., to those with small leaves 
and solitary flowers as L. microcuspis Baker and L. stocksii 
Hook.; Viscum consists mainly of species of condensed habit, 
small leaves often reduced to scales, and small green unattractive 
flowers and more or less simplified embryos; finally Arceutho- 
hium consists of reduced almost leafless parasites becoming 
slightly yellowish in color with small solitary flowers. In this 
family, however, the plants still contain chlorophyll. In the 
Convolvulaceae the parasitism has become so great in the 
genus Cuscuta that it has completely lost all traces of chloro- 
phyll, except in the stems of C. reflexa, Roxb. (Hooker in Bot. 
Mag. t. 6566). From this species we have gradations to others 
with thick yellow stems like C. exaltata, Engelm.; others with 
slender yellowish or red stems as C. epiliniim Weihe and C. 
epithymum Murr, pale yellow in C. arvensis Beyrich, and whitish 
or pale yellow in C. cephalanthi Engelm., and finally to white in 
C. epithymum var. alba. The leaves are in all cases reduced 
to microscopic scales; the flowers are small but clustered to- 
gether; the first or central flowers are five-parted, the lateral 
ones often four-parted (15), and the embryo is so reduced that 
it shows no trace of cotyledons. 

43 



44 Henderson — Comparative Study oj Pyrolaceae and 

The writer, however, is concerned with saprophytism alone. 
In the Burmanniaceae, for example, the genus Biirmannia shows 
transitions from green leafy plants with several racemose flowers 
as B. longijolia Becc. to gradually condensing forms, as B. 
azurea Griff, with a rosette of tiny herbaceous membranous 
leaves and one to four flowers, then to more simplified forms, 
as B. tuherosa and B. Candida, and finally, most simplified of all, 
to the genera Thismia and Gymno siphon. The stems become 
feeble, less green, then reddish or brownish. The green leaves 
become reduced to herbaceous membranous leaves, then to 
scales; the flowers become reduced in number and size; the ovary 
becomes reduced from a three-celled condition with central 
placenta to a more primitive one-celled state with parietal 
placentas (Gymnosiphon) ; there is an increase in the number of 
ovules, but a reduction in their size; the seeds are reduced in 
size and structure; the reserve albumen is reduced in size and 
number of cells, and the embryo from a typical monocoty- 
ledonous one to a formless mass. 

The writer would claim that essentially the same set of changes 
can be traced in genera of the Orchidaceae and Gentianaceae. 
Green autophytes, passing by gradual changes to colorless 
saprophytes, occur in both of these. Now, among systematists 
of the past, there has been no thought of putting the sapro- 
phytic plants of the above three groups in separate families. 
Why then, it may be asked, should the Pyrolaceae and Mono- 
tropaceae be separated from the Ericaceae? It will be the 
writer's aim in the present paper to prove, alike on morpho- 
logical and physiological, as well as taxonomic grounds, that 
these three families all show so close a relationship that to view 
them as separate families is unnatural and artificial. 

Jussieu (37) considers all ericaceous plants under the two 
orders — Rhododendra and Ericae — the latter including Pyrola. 
Lindley (46) places them in three orders — Ericeae, Vaccinieae, 
and Pyrolaceae (including Monotropaceae). De Candolle (10) 
makes four orders — Vaccinieae, Ericaceae, Pyrolaceae, and 
Monotropeae. Gray (25) considers the Vaccinieae, Ericineae, 
Pyroleae, and Monotropeae as suborders of the Ericaceae. 
Baillon (3) considers the Pyroleae, Monotropeae, and Ptero- 
sporeae as three of the eighteen tribes under the Ericaceae. 
Bentham and Hooker (4) make three orders, the Vacciniaceae, 



Monotropaceae with Reference to Ericaceae 45 

Ericaceae (including as a tribe the Pyroleae), and the Mono- 
tropeae. Drude (12) gives two families — the Ericaceae and 
the Pyrolaceae (including the Monotropaceae). Britton and 
Brown (6) consider as separate families the Pyrolaceae, Mono- 
tropaceae, Ericaceae, and Vacciniaceae. Small (72) considers 
the Pyrolaceae, Monotropaceae, and Ericaceae as distinct 
families. So we see that the Pyrolaceae and Monotropaceae 
are united by the majority of systematists, yet the gulf between 
the two is really more difficult to bridge than that between 
the Ericaceae and Pyrolaceae. 

Drude in "Die Natiirlichen Pflanzenfamilien" (12) gives as 
his reasons for not including the Pyrolaceae and the Mono- 
tropaceae in the Ericaceae: (i) the remarkable placentation, 

(2) the regular form of the seed and embryo in the Ericaceae, 

(3) the lacking disc, (4) the dehiscence of the anthers, (5) the 
simple pollen of the Monotropeae. 

(i) In typical Ericaceae the ovary is five- or four-celled 
with a central placenta. Two lobes bearing the ovules extend 
into each cell of the ovary. It is generally considered to be 
five-celled in the Pyrolaceae also, but the division is not com- 
plete. The parietal placentae borne in on the dividing walls 
fuse at the center for about half the length of the ovary. This 
basal half is exactly similar to that of the Ericaceae, two pla- 
cental lobes bearing ovules extending into each cell. Above 
this the placentae fail to meet at the center and the upper half 
becomes one-celled with bilobed parietal placentae. This con- 
dition is true of C. umbellata, C. maculata, P. rotundifolia (P. 
americana Sweet), P. elliptica, P. secunda* P. minor, P. chlor- 
antha, P. aphylla, Moneses uniflora* of the Pyrolaceae; also of 
Allotropa virgata, Pterospora andromedea, Sar codes san guinea, 
Schweinitzia odorata, Mojiotropa hypopitys, M. uniflora, of the 
Monotropaceae. The division Pleuricosporeae of the Mono- 
tropaceae is considered one-celled in the ovary. Neivberrya 
is described by Torrey in the Ann. Lye. N. Y. VII 55 (1864): 
"Placentae four with broad divergent lamellae which meet 
adjacent edges, ovuliferous both sides giving the appearance of 



* P. secunda and Moneses uniflora are almost completely five-celled. 
Owing to the sunken style the distance through which the ovary is one- 
celled is very short. 



46 Henderson — Comparative Study of Pyrolaceae and 

four exterior cells surrounding a central large one." The writer 
examined material of Newherrya spicata A. Gray and N. con- 
gesta (A. Gray) Torr, and found an exactly similar condition 
to that in the rest of the family — i.e., that the ovary at the base 
is five-celled owing to the fusion of the placentae and that 
owing to a lack of fusion further up the ovary became one-celled 
with parietal placentae. Pleimcospora fimbriolata A. Gray 
shows the most simplified condition in regard to the ovary. 
It is four-celled only at the very base for about one-sixth the 
distance, then one-celled with four parietal placentae. 

(2) In typical Ericaceae the seed is very small, never larger 
than 1-2 mm. The seed covering is double, there is a richly 
developed endosperm in which is embedded a straight embryo 
which is one-third to two-thirds the length of the seed. The 
embryo always shows a root, an axis, and two cotyledons. The 
seeds in the Rhododendroldeae-Ledeae, the tribe nearest in 
character to the Pyrolaceae, are winged, very small, and con- 
tain a very small embryo. These seeds are very similar to 
those of the Pyrolaceae, except that in the latter the embryo 
itself is very much smaller, simplified to a few cells, and with 
no dififerentiation into root or cotyledons. The amount of 
albumen in which the embryo is embedded is also reduced. 

(3) There is in practically all typical Ericaceae, at the base 
of the ovary, a nectar-secreting disc which may be present 
as a circular ring or a crenulately lobed swelling. Miiller has 
illustrated those of Arctostaphylos, Calluna, Erica, Azalea, Rho- 
dodendron, and Warming those of Andromeda, Cassiope, Phyllo- 
doce, in Knuth's "Handbook of Flower Pollination" (42). Drude 
(12) seems to indicate that it is lacking in the Pyrolaceae and 
Monotropaceae and gives this as a reason for separating them 
from the Ericaceae. In C. timhellata and C. macidata it is 
present as a nectar-secreting ring at the base of the ovary. In 
the genus Pyrola the disc varies. According to Drude (12) it 
is present as a ten-rayed nectar-secreting organ in P. (Moneses) 
uniflora, but Miiller (42) states that there is no nectar secreted 
by M. uniflora and figures no nectaries. The writer sees no 
trace of nectaries in the material examined. Drude states 
that the disc is present as ten small nectaries at the base of the 
ovary in P. seciinda and is absent or rudimentary in all of the 
other species. The writer found very small swellings that 



Monotropaceae ivith Reference to Ericaceae 47 

appeared glandular at the base of the ovary in P. secunda, P. 
chlorantha, P. aphylla, but none in P. rotundifolia, P. elliptica, 
and P. minor. 

In the Monotropaceae Drude says "Disc present, or replaced 
by nectaries, rarely lacking." In Allotropa, according to Torrey 
and Gray (77), it is minutely ten-lobed. The writer finds ten 
slightly downward directed lobes; in Monotropa there are 8-10 
downward directed nectaries; in Sarcodes* there are ten swell- 
ings at the base of the ovary; in Pterospora Drude reports that 
it is absent. 

In Schweinitzia there are ten lobes between the stamens. 
Drude states that in the Pleuricosporeae the disc is entirely 
lacking in Newberrya, Pleuricospora, and Cheilotheca. This 
appears to be true of Pleuricospora but in Newberrya the writer 
finds that ten nectaries are present at the base of the ovary, 
very similar to those of Monotropa. No material of Cheilo- 
theca could be obtained for examination. 

(4) In the Pyrolaceae and Monotropaceae the dehiscence of 
the anthers follows one of these types. 

1 . Apical porous — with more or less developed tubes in Chima- 
phila, Pyrola, Moneses, Sarcodes, Schweinitzia. 

2. Longitudinal — Allotropa, Pterospora, Pleuricospora, New- 
berrya, Cheilotheca. 

3. Transverse — Monotropa. 

In the Ericaceae apical porous and longitudinal dehiscence 
seem to be about equally distributed throughout the family 
and even in the same group, i.e., in the Rhododendroideae-Ledeae 
Bejaria and Ledum have apical porous, Elliottia and Clado- 
thamnus longitudinal dehiscence of the anthers. Transverse 
dehiscence of the anthers also occurs in the Ericaceae. The 
group Arbutoideae-Andromedeae, according to Drude (12), has 
pores or slits at the apex or transverse slits. 

(5) The Pyrolaceae and Ericaceae have tetrad pollen grains, 
the Monotropaceae simple pollen grains. However Pyrola 
secunda, a typical member of the genus, has simple pollen grains 
so that even this distinction does not entirely hold true. 



* Drude reports no disc in Sarcodes; Oliver (58) that the disc is present. 
The writer's material confirms the latter. 



48 Henderson — Comparative Study of Pyrolaceae and 

We see, therefore, how artificial, untrustworthy, and inter- 
blending these distinctions are. There are also other great 
resemblances between the Ericaceae and the Pyrolaceae and 
Monotropaceae. All of the Ericaceae are shrubby rarely arbor- 
escent, often sub-shrubby. The Pyrolaceae as a whole are sub- 
shrubby, Chimaphila umhellata often becoming very thick, 
woody; most of the genus Pyrola is sub-shrubby also, with the 
exception of Pyrola or Moneses uniflora. The Monotropaceae 
are essentially saprophytic herbs, but they perennate from 
underground woody parts. 



Historical 

Owing to the complete historical references on the subject 
of mycorhiza in general given by Gallaud (22) and Rayner (64), 
the writer has confined herself to those dealing with mycorhiza 
in the Ericaceae alone. 

As early as 1842, Rylands (67) investigated the "byssoid" 
substance on the roots of Monotropa hypopitys and came to the 
conclusion that it was a fungus living on the roots. In 1856- 
1865, Chatin (6) described M. hypopitys as a parasitic plant. 
In 1873, Drude (11) investigated the roots of M. hypopitys, 
coming to the conclusion that the plant is saprophytic. In 
1 88 1, Kamienski (38, 39) also described and figured the con- 
dition in M. hypopitys, and formulated the hypothesis that 
there existed a symbiosis between the plant and the fungus. 
During the last thirty-five years, it has been shown that sapro- 
phytism is widespread throughout the Ericaceae proper. Frank 
(19), in 1887, described the appearance of ericaceous roots 
infected by fungi. He mentions particularly the much en- 
larged epidermal cells, filled with knots of hyphae, the absence 
of root hairs, and the reduction of the root cap. Those men- 
tioned as possessing endotrophic mycorhiza are Andromeda 
polifolia, Vaccinium oxycoccus, V . uliginosum, V. macrocarpum, 
V. myrtillus, V. vitis-idaea. Ledum palustre, Calluna vulgaris, 
Rhododendron ponticum. Azalea indica, Empetrum (included by 
him under Ericaceae). He says, however, that they have not 
been found in Pyrola and that in Monotropa the mycorhiza is 
ectotrophic. 



Monotropaceae with Reference to Ericaceae 49 

In 1907, Charlotte Ternetz (77), in a paper "Ueber die As- 
similation des Atmospharisches Stickstoffes durch Pilze," used 
as the basis for her experiments endotrophic fungi in the roots 
of Andromeda polifolia, Oxycoccus palustris, Calluna vulgaris, 
Erica carnea, E. tetralix, Vaccinium myrtillus, V. vitis-idaea, 
V. nliginosum. She states that, although hyphae are present 
in the seed coats, no trace of the fungus can be found in any 
other living part of the plant, except the roots. Rayner (63) 
in an article on "Obligate Symbiosis in Calluna vulgaris'' traces 
the fungus from the roots through the whole plant to the seed. 
She proves that the symbiosis in Calluna is obligate, for, unless 
the seedlings become infected, they die. She also states that 
ovarial infection is present in Ledum palustre, Rhododendron 
ponticum (garden var.), Rhododendron indicum {Azalea indica, 
garden var.), Leiophyllum buxifolium, Kalmia angustifolia, Pieris 
floribunda, P. japonica, Gaultheria acutifolia, Arctostaphylos 
uva-ursi, Arbutus unedo, Vaccinium vitis-idaea, Pentaptergyium 
serpens, Calluna vulgaris, Erica carnea. Jean Dufrenoy (14) 
in "The Endotrophic Mycorhiza of Ericaceae" has reported 
the presence of a fungal mycelium throughout the entire plant 
of Arbutus unedo. 

All these cited are, however, still green, and have abundant 
leafy branches with well-formed clusters of typically ericaceous 
flowers. It seems that the more simplified greens and the 
yellow and white saprophytic forms have been separated from 
the Ericaceae to form the Pyrolaceae and Monotropaceae, and 
that these three families in the order named form a continuous 
series from autophytic to completely saprophytic plants. 

An aim of this paper will be to ascertain how far saprophytism 
has caused gradual and traceable degradation changes similar 
to those of the Burmanniaceae, Orchidaceae, and Gentianaceae. 
Practically all typical ericaceous plants are shrubs, rarely trees; 
some like Cassiope are sub-shrubby; in the Pyrolaceae Chima- 
phila and the larger species of Pyrola are sub-shrubby; but 
Moneses uniflora would hardly be regarded as other than a 
herb; in the Monotropaceae all of the genera are herbaceous. 
Another aim will be to find characters which unite the most 
degraded saprophytes with the autotrophic Ericaceae, thereby 
proving that the separation of the Pyrolaceae and Monotro- 
paceae from the Ericaceae is artificial. 



50 Henderson — Comparative Study of Pyrolaceae and 

Methods and Materials Used 

In making comparisons, care was taken to section the material 
at exactly the corresponding point in each of the plants. 

Sections of freshly gathered or of alcoholic material of rhi- 
zomes, stems, and leaves were examined unstained in acetic 
acid, or stained in safranin and methyl green and examined in 
balsam. 

Fresh root tips were examined in a solution of iodine in potas- 
sium iodide to differentiate the fungus. Otherwise, all roots 
and flowers were fixed in weak chrom-acetic acid and embedded 
in paraffin. These were stained in safranin and gentian violet. 

Pieces of the ascending axis of Monotropa tmiflora and M. 
hypopitys were bleached and macerated in a mixture of 50% 
nitric acid and potassium nitrate in order to examine the epi- 
dermis. 

Herbarium material of the flowers was prepared for exam- 
ination by the method used by R. C. McLean (52). 

The following is a list of the plants used, and localities from 
which they were collected, for use in this comparison: 

Fresh Material 

Chimaphila timhellata — Hosensack, Pa., Analomink, Monroe 
Co., Pa., Somers Point, N. J., Glendora, N. J., Woods Hole, 
Mass., Greenwood Lake, N. Y. 

Chimaphila maculata — Hosensack, Pa., Crum Creek, Dela- 
ware Co., Pa., Almonessen, N. J., Blackwood, N. J., Somers 
Point, N. J., Woods Hole, Mass. 

Pyrola rotundifolia — Hosensack, Pa., Crum Creek, Delaware 
Co., Pa., Analomink, Monroe Co., Pa., Woods Hole, Mass. 

Pyrola elliptica — Hosensack, Pa., Crum Creek, Delaware Co., 
Pa., Analomink and Paradise Valley, Monroe Co., Pa., Woods 
Hole, Mass. 

Moyieses uniflora — Plants collected by Miss Mary Garley near 
Claremont, N. H. 

Monotropa hypopitys — Analomink, Pa., Somers Point, N. J., 
Woods Hole, Mass. 

Monotropa uniflora — Analomink, Pa., Blackwood, N. J., 
Woods Hole, Mass. 

Kalmia latifolia, Kalmia angustifolia, Dendrium buxifolum, 
Cassandra calyculata — Clementon, N. J. 

Ledum groenlandicum — Peakes Island, Maine, collected by 
Miss A. M. Russell. 



Monotropaceae with Reference to Ericaceae 51 

Alcoholic Material 
Sarcodes sanguinea — Collected by Miss Edith M. Farr in 
California. 

Herbarium Material 

Descriptions of the plants and microscopic studies of the 
flowers of Pyrola secunda, P. minor, P. chlorantha, P. aphylla, 
Pterospora andromedea, Schiveinitzia odorata, Pleiiricospora fim- 
briolata, have been made from the Herbarium of the University 
of Pennsylvania. Those of Allotropa virgata, Newberrya spicata, 
N. congesta, were examined from the Herbarium of the Phila- 
delphia Academy of Natural Sciences. 

As it was impossible for the writer to get fresh material of 
the roots of Moneses nniflora, the Herbarium of the Bronx 
Botanical Garden, through the kindness of Dr. F. W. Pennell, 
sent several herbarium sheets for examination. 

Through the kindness of Mr. W. R. Taylor, the writer was 
given the opportunity of examining sections of the leaves and 
stems of ericaceous plants, collected on Mount Washington by 
him, including Cassiope hypnoides, Chiogenes hispidula, Ledum 
groenlandicnm, Loiseleuria procumbens, Rhododendron lapponi- 
cum, Vaccinium idiginosum, V. vitis-idaea. 

The writer wishes to state here her deep appreciation of the 
assistance given and the constant interest shown by Dr. J. M. 
Macfarlane in the preparation of this paper. 

The Underground Root and Stem Systems 

The mature underground system in C. iimbellata consists of 
horizontal, thick, white runners or rhizomes bearing scales, in 
the axil of which occur two buds, the first developing into an- 
other branch or runner, the second into an adventitious root. 
The end of the runner finally pushes above the surface of the 
ground and produces a whorl of leaves. The roots are very 
small, wiry, and do not branch profusely. This method of 
underground stem branching is characteristic of a number of 
typical Ericaceae. Warming (84) describes and figures it for 
Andromeda polifolia L., Vaccinium myrtillus L., V. uliginosum L., 
V. vitis-idaea L., V. oxycoccus L. (figs. 19, 27, 29, 32, 35). 

The underground systems of C. mactdata, Pyrola rotiindifolia, 
P. ellipiica, P. secunda, P. minor, P. chlorantha are similar to 
that of C. umbellata (Warming (84) figs. 38, 39). 

In P. aphylla, it consists, according to Holm (30) of runners 
as in the other Pyrolas, one of which rising to the surface may 



52 Henderson — Comparative Study of Pyrolaceae and 

produce green leaves, another an inflorescence with only scale 
leaves. Holm and Drude (12) report the presence of adven- 
titious buds arising from the roots and forming flowering or 
vegetative shoots, Irmisch (30) reports this same reproduc- 
tion by root shoots in P. secunda and P. chlorantha. Holm 
states that this also occurs in P. picta, C. nmhellata, and C. 
maculata, though none of the writer's material of the latter 
genus shows this. 

This reproduction by adventitious buds from the roots in 
P. aphylla forms a connecting link with the condition in Moneses 
uniflora. Warming (85) and Irmisch (32) state that in this spe- 
cies there is a horizontal root from which arises a leaf-bearing 
shoot terminating in an inflorescence. Warming states that 
a root arises from the horizontal one at the base of each shoot. 
In other words, there is no rhizome present; the horizontal 
root here takes over the function of the rhizome in producing 
leaf- and flower-bearing shoots. The occasional production of 
adventitious buds on the roots of P. aphylla has become habitual 
in Moneses uniflora — this being the only method of vegetative 
reproduction in the latter. The main root of M. uniflora re- 
sembles the rhizomes in the Pyrolas excepting for the absence 
of scales on it; normal secondary roots are produced from the 
root at the base of the vegetative shoot and at irregular inter- 
vals along its course. 

MacDougal (48) states that '' Pterospora andromedea is fur- 
nished with an ovoid mass of dark brown club-shaped roots 
which ramify densely through a space of not more than 150-200 
cc. in which the roots occupy a much greater proportion of the 
volume than the included humus." There are several primary 
roots which branch and rebranch, all intertwining to form a 
"compact globoid mass." He states that inflorescence buds 
arise from the horizontal root. 

Oliver (58) has described the appearance of the root system 
of Sar codes sanguinea. He states: "The roots are attached 
in great quantities to the bases of the flowering shoots and 
form large and intricately woven masses of 'coralline' appear- 
ance." The main axis bears numerous secondary roots which 
in turn produce tertiary ones. The surface is of a "deep brown 
color," showing a "certain roughness of texture" due to their 
being invested with a fungal sheath. He states that the plant 
is vegetatively reproduced by buds from the roots. 



Monotropaceae with Reference to Ericaceae 53 

In Monotropa there is a similar mass of roots. The main 
root is thick, horizontal, giving rise to inflorescence buds and 
to secondary roots, which are short, fleshy, and intertwine 
closely to form a compact mass. Drude (11), Kamienski (39), 
Queva (62) call this horizontal structure a root. Peklo (59) 
calls it a "Rhizomaste." The structure is so simplified that 
it is difficult to determine whether it is a root or a rhizome. 

There is therefore in the underground root and stem system 
a gradual condensation and simplification from genera like 
Chimaphila and Pyrola, which have, as in certain typical Erica- 
ceae, extensively branching rhizomes from which are produced 
the vegetative axes as branches in the axils of scales , to Moneses, 
where the rhizome is completely lacking and the vegetative 
axes arise endogenously from an old horizontal root which 
closely resembles a rhizome in appearance; to Pterospora, Sar- 
codes, and Monotropa, where the horizontal root has become 
very much condensed, thickened, and fleshy, also producing 
vegetative buds endogenously. The roots, from being thin, 
wiry, and sparsely branching in Chimaphila and Pyrola, have 
the primary root enlarged and thickened in Moneses, Pterospora, 
Sarcodes, and Monotropa. The secondary roots begin to show 
a slight swelling at the tip in P. rotundifolia and P. elliptica. 
This swelling becomes greater, secondary roots become short- 
ened, thickened, and more fleshy and much more numerous, 
so that there is a close compact mass of roots in Pterospora, 
Sarcodes, and Monotropa. 

The Root 

In Chimaphila umhellata, sections of the root tip (fig. i, i) 
show a short root cap of 4-5 layers at the very tip. This to- 
gether with the epidermis arises from a common tissue, there 
being only three regions of growth, the calyptro-dermatogen, 
the periblem, and the plerome. The epidermal cells at the tip 
are small, indistinguishable in size from the others, but soon 
show gradual increase in size, particularly in a radial direction — 
the radial width becoming three to four times the length. This 
gradual increase occurs under the root cap, this region never 
being infested by fungi. Above the root cap, the cells suddenly 
become larger and square in section. These cells are infested 



54 Henderson — Comparative Study of Pyrolaceae and 

by septate hyphae which appear as balled-together masses in 
the epidermal cells. All cells and all roots are not equally 
infested — some roots show no trace of hyphae; others show a 
few epidermal cells with two or three hyphal threads; others 
show some epidermal cells packed full of masses of hyphae 
and a hypertrophied nucleus, and cells in the same root with 
normal nucleus and cytoplasm. Rommel (65) states that there 
are no hyphae present in the roots of C. umhellata and that root 
hairs are present. The writer has examined material from 
many localities, and has found some roots of each plant infested 
with hyphae and has never found any traces of root hairs. 
Beneath the epidermis are one to two layers of elongated cor- 
tical cells crowded with typical aggregate starch grains com- 
posed of two to six simple grains, each with a distinct hilum. 
These appear in safranin-stained sections as hyaline grains with 
red staining hila. In the same or neighboring cells these grains 
appear slightly yellowish, but still with a distinct hilum, then 
yellowish brown with no hilum apparent; and finally the indi- 
vidual grains merge together to form a sac of brownish material. 
The secondary roots are produced endogenously. 

The root tip of C. maculata has much the same appearance 
as that of C. umbellata, except that the epidermal cells of the 
former beneath the root cap are longer compared with their 
radial width; these above the root cap are larger in comparison 
with the other cells than are those in C. umbellata, are more 
often, and, to a greater extent, infested with hyphae (Fig. 2, i); 
and also in those cells not filled with hyphae there appear one 
to three large bladders, the walls of which are light yellowish 
in color. These may be the remains of the nuclear membrane 
after the nucleus has been completely destroyed by the fungus, 
or enlargements formed by the hyphae similar to those described 
by Groom (28) in the mediocortex of the absorbing organ of 
Thismia asero'e and by Gallaud (22) in the roots of Colchicum 
autumnale. The writer however did not find any hyphae 
attached to these bladders. 

In Pyrola rotundijolia (Fig. i, 2) the root cap is strongly 
reduced, there being only one to two layers of cells. The aspect 
of the cells at the tip, under the root cap region, is much the 
same as in the two species just described; but above the root 
cap the epidermal cells swell out enormously, much more than 



Monotropaceae with Reference to Ericaceae 



55 




Fig. 1. Longitudinal sections (X250) of root-tips of 

1. Chimaphila umhellata 

2. Pyrola rotundifolia 

3. Monotropa hypopitys 

4. Monotropa uniflora 

C = root cap, E = epidermis, F = free hyphal filaments, S = hyphal 
sheath. 



56 Henderson — Comparative Study of Pyrolaceae and 

in C. iimhellata, or C. maculata, and practically every cell be- 
comes filled with balled-together masses of hyphae. There 
also occurs on the outside of the epidermis a network of inter- 
twining hyphae (Fig. 2, 2), forming a sheath 5 from which 
extend separate filaments F which apparently take the place 
of root hairs in supplying the root with water. There is a 
connection between these outer hyphae and those in the epi- 
dermal cells. These hyphae grow between and around the 
epidermal cells, until they surround them on all sides, except 
the interior; so that a tangential section shows epidermal cells 



^'?®^^^ifc-7 





Fig. 2. Longitudinal sections (X300) of epidermal cells of root tip. 

1. C. maculata 

2. P. rotiindifolia 

F = free hyphal filaments, S = sheath. 

separated by a pseudoparenchyma, much like that seen in 
Monotropa. There is apparently no invasion of any layer 
beneath the epidermis. Kramar (44) has described all stages 
of the growth of the mycorhiza. The walls of the epidermal 
cells first become infested with hyphae forming a pseudoparen- 
chyma between the cells. Later, when the epidermal cells 
become full size the hyphae penetrate the cell wall, make direct 
for the nucleus and begin to form a ball around it. The nucleus 
finally becomes hypertrophied and lifeless. When this occurs 
and the cell is packed full of hyphae they penetrate the cell 
wall again and spread out over the surface. Before this occurs 



Monotropaceae with Reference to Ericaceae 57 

Kramar says that the fungus is only a parasite drawing its 
nourishment from the plant. After the outer covering is formed, 
however, the fungus can then take the place of root hairs and 
absorb water for the plant. It may also give a part of its own 
assimilated food to the plant. Frank observes that as the 
fungus dies each year the plant could then absorb its protein 
content. Kramar also describes the contents of the subepi- 
dermal cells, that they are coarsely granular and that these 
cells represent a storage place where the nutritive material, 
taken in by the mycelium, lies until ready to be transferred to 
where it is to be used. He probably saw the starch grains 
similar in appearance to those of Chimaphila when they had 
become disintegrated to the extent of not showing a hilum. 

Pyrola elliptica has practically the same appearance as P. 
rotundifolin. P. seciinda is reported to have fungal hyphae 
by Irmisch (32), Rommel (65), Andres (2), Petersen (60); 
P. minor by Kramar (44) and Petersen (60). 

P. aphylla is described by Holm (30) as having the root free 
from hyphae. This seems rather improbable in view of the 
fact that all the other members of the genus have been reported 
to have hyphae in the roots. The writer has not been able to 
get fresh material of this for examination. 

Moneses tiniflora is reported by Irmisch (32) to have fungal 
hyphae in the roots. 

In Monotropa hypopitys (Fig. i , 3) Kamienski (39) and Drude 
(11) describe the root tip as having one to two layers of root 
cap, Drude claiming that in one variety — hirsuta — there are 
two layers, and in glabra only one. Kamienski, however, says 
that the number of layers may vary in the same individual. 
The material examined shows one to two layers of root cap, the 
outer layer crushed and flattened. All the cells at the tip are 
very much alike, differentiation into plerome and periblem 
occurring some distance back from the tip. Kamienski (39) 
and Peklo (59) have given complete descriptions and accurate 
figures of the root tip of M. hypopitys. In the Chimaphila and 
Pyrola species described the fungus does not seem to invade the 
root cap region either in the root cap itself, over its surface, 
or in the epidermal cells beneath. In M. hypopitys, though the 
epidermal cells under the root cap and the root cap cells are 
not infested, the mycelium extends over the surface of the root 



58 Henderson — Comparative Study of Pyrolaceae and 

cap — though thinner here than over the rest of the root. As 
in P. rotundifolia there is a development of pseudoparenchyma 
between the epidermal cells and a continuation of this on the 
exterior forming a sheath much greater in thickness than in 
P. rotimdifolia. This outer sheath consists of two regions, the 
inner composed of closely intertwined hyphae, the outer of 
more loosely arranged threads that stray out into the soil. 
Kamienski claims that the hyphae never penetrate the epi- 
dermal cells, but that sometimes in older parts a hypha may 
penetrate an epidermal cell, which it fills with a brown content. 
He also says that over the apex the sheath thins out so that 
there are only several isolated filaments. MacDougal and 
Lloyd (50) state that the hyphae do penetrate the epidermal 
cells, forming swollen vesicles, and that the root tip is completely 
invested by a thin fungal sheath. Peklo figures the penetra- 
tion of haustoria into the epidermal cells. He states that 
haustoria are present in all infested roots of this species. The 
hyphae do not completely fill the cell as in P. rotundifolia be- 
cause there is present a vacuole of yellowish brown substance. 
Drude calls this a pigment ; Kamienski notes its presence in dead 
cells only, and states that it is tannin; Bokorny (5) that it is 
tannin in the living cells. The latter, noting that there seems 
to be no difference in the quantity of this material from the 
youngest to the oldest epidermal cells, concludes that it cannot 
have anything to do with the nutrition of the fungus but that 
it serves, on account of its strongly concentrated tannin con- 
tent, as a protection against the hyphae. Peklo also notes 
that beside this the resistant cuticle of the layer beneath keeps 
the fungus from penetrating further into the root. He claims 
that there are two ecological varieties of M. hypopitys, one 
living in humus, with the roots near the surface; the other in 
loamy soil, the roots deep underground. In the former, he 
says that hyphae are always present and indispensable to the 
life of the plant; in the latter, there are no mycorhiza in a great 
majority of the roots. The writer's material, however, was 
collected in a loamy soil with a surface covering of humus, the 
roots about 5 dm. below the surface, and all were strongly 
infested with hyphae. One difference between the epidermal 
cells of this species and those of P. rotundifolia is that they are 
not enormously enlarged in comparison with the rest of the 



Monotropaceae with Reference to Ericaceae 59 

cells — in fact the epidermal cells in M. hypopitys are smaller 
than those of the layer beneath. MacDougal and Lloyd (50) 
report the presence of starch in the cortex of the roots of Mono- 
tropa near the tip, though the material examined by the writer 
failed to show this. According to Kamienski, secondary roots 
arise endogenously as in the Pyrolaceae. 

The root tip of M. uniflora (Fig. 1,4) is quite similar to that 
of M. hypopitys, except that at the apex the regions of growth 
are even less distinguishable; the pseudoparenchyma between 
the walls appears to be better developed; and the outer layer 
of the sheath formed by the intertwining hyphae does not thin 
out over the apex as in M. hypopitys, but continues as a layer 
of the same thickness completely around the root tip. This 
has been described and figured by MacDougal and Lloyd (50) 
(p. 10, PI. 11). The root cap consists of one to three 
(MacDougal and Lloyd 1-4) layers of flattened cells filled with 
deeply staining material. The cells appeared crushed in all of 
the root tips examined. The area which the root cap covers is 
exceedingly limited. MacDougal and Lloyd have figured all 
stages of the penetration and development of the fungus in the 
epidermal cells. The nucleus becomes deformed; the hyphae 
form grape-like clusters, which they consider to be atrophied 
reproductive branches. They also state that starch grains 
occur in the outermost layer of the cortex and that secondary 
roots arise from the third layer of the cortex. 

Oliver (58) has described and figured the root tip of Sarcodes 
sanguinea Torr. The appearance is very like that of Monotropa 
uniflora. In Sarcodes the root cap is better developed. Oliver 
figures five layers. The fungus surrounds each epidermal cell, 
and forms a sheath of hyphae on the surface. He states that 
the hyphae never penetrate the epidermal cells, but he also 
mentions that the nuclei of the epidermal cells are modified into 
rod-like structures. MacDougal and Lloyd mention the pres- 
ence of the mantle of mycelium that extends completely around 
the root tip; that this is composed of two regions as in Mono- 
tropa and that the hyphae penetrate the epidermal cells. In 
the layer beneath the epidermis Oliver figures a few starch 
grains. He reports that secondary roots arise exogenously. 

MacDougal (48) in "Symbiotic Saprophytism" and Mac- 
Dougal and Lloyd (50) have described the root tip of Ptero- 



6o Henderson — Comparative Study of Pyrolaceae and 

spora. It is coated with a dense brownish septate mycelium 
which pushes in between the epidermal cells, penetrates them, 
forming irregular vesicles and distorted nuclei, and even enters 
the sub-epidermal layers. A root cap is present, and MacDougal 
states that this resembles that of Sarcodes, in having more than 
two layers. The mycelium covers the root cap and penetrates 
the older cells in free tips, but penetrates beneath the root cap 
in those roots that are in the center of the clump. He states 
that starch is present in the outer cortical layers and that sec- 
ondary roots arise exogenously. 

Thus in the root tip region we have a gradually ascending 
series in the amount of fungus present from C. umhellata, with 
the epidermal cells of some roots with no hyphae — other roots 
with hyphae, but not in every cell; to C. macidata with a still 
greater number of the epidermal cells filled with hyphae; to 
P. rotundifolia and P. elliptica with all of the cells infested and 
with a beginning of a sheath of intertwined hyphae around the 
root tip; then in M. hypopitys an increase in the width and 
extent of this sheath and a division of it into two zones — the 
outer a more loosely interwoven mass of hyphae, the inner 
more compact; finally in M. uniflora a still greater width of 
the fungal sheath. The descriptions of the presence of hyphae 
in Sarcodes and Pterospora show a great resemblance to Mono- 
tropa, but not having material to examine the writer cannot 
say which has the larger amount of mycelial investment. In 
Chimaphila the hyphae are probably not of much use to the 
plant as the threads are only in the epidermal cells and do not 
extend out over the surface. The development of an outer 
sheath of hyphae in Pyrola and its great increase in amount in 
Monotropa, Sarcodes, and Pterospora would allow the fungus 
to be of more use to the plant and that this is true is indicated 
by the lack of green coloring matter in the last three men- 
tioned. 

Sections both longitudinal and transverse of the oldest por- 
tion of the root were examined in all of the preceding. In 
C. umhellata, as the root becomes older, the hyphae penetrate 
more between and into the epidermal cells, completely filling 
them all. The nuclei become disintegrated, the walls thicker, 
the cells die and finally fall off. The outermost layer of the 
cortex may have some of its cells penetrated by the fungus, 



Monotropaceae with Reference to Ericaceae 6i 

but this is rare. The walls of the outer cells of the cortex also 
become thickened and these also fall off. Meantime the 4-5 
arch bundle system has undergone secondary thickening. New 
xylem cells have developed so that there is formed a solid central 
cylinder of wood enclosed by a few layers of thin-walled phloem 
cells. These roots are perennial and annual rings of wood 
are laid down. The oldest one examined was found to have 
four years of growth. The largest part of the wood seems 
to be composed of pitted vessels with a few spiral ones. 

C. maculata, P. rotundifolia, and P. elliptica showed prac- 
tically the same appearance except that none of the mater- 
ial examined was old enough to have formed annual rings 
or to have had the epidermis entirely dead and sloughed off. 




Fig. 3. Transverse section root of Moneses uniflora showing central xylem 
tissue X 300. 

In Moneses uniflora the epidermal cells become filled with 
hyphae and fall off. Hyphae may penetrate into the outer 
layers of the cortex. The wood is at first diarch — a few remain- 
ing cells seem to indicate that this is a reduction from a tetrarch 
condition (Fig. 3). Secondary wood is formed. 

MacDougal and Lloyd (50) have described the structure of 
the old root of Sarcodes and Pterospora. The epidermis becomes 
completely filled by the fungus and falls off. After this the 



62 Henderson — Comparative Study of Pyrolaceae and 

subepidermal cells divide radially to form a wider cortex. "The 
central cylinder of Sarcodes and Pterospora is least reduced 
and its development may be traced in them with some certainty. 
Here the 5-6 xylem bundles alternate with the simple phloem, 
enclosing a well marked medulla. The first step in the sec- 
ondary growth is the sclerotization of the medulla, and is fol- 
lowed by the lignification of this tissue in Sarcodes. Next the 
phloem gives rise to a cambium which develops wood inter- 
nally, and bast on the outside. The latter consists for the 
greater part of elongated elements of narrow lumen which do 
not undergo any marked thickening of the walls. The wood 
formed by the cambium joins directly on to the lignified medulla. 
The inner ends of the primary medullary rays also undergo 
sclerotization to some extent, but the outer portions show as 
broad bands one or two layers in thickness with the character- 
istic appearance of being compressed tangentially. The advance 
of the cambium is at first fairly regular, as the cambium zone 
moves outwardly beyond the first ring formed, the transforma- 
tion into vessels is accomplished with such disturbance or vari- 
ance from the customary manner that it is not possible to draw 
a line separating the two regions. Furthermore, some of the 
cambium cells of great size remain as great thin-walled elements 
in the wood, or these may be arranged in radial lines simulating 
tertiary rays. A region of cambiform elements, four to six 
layers in thickness, may be seen entirely surrounding the xylem. 
The structure formed by this behavior of the cambium resembles 
that of a stem, and indicates that the roots of the two genera 
in question may attain an age of two years or more." 

In Monotropa hypopitys, the oldest part of the root is the 
horizontal portion that gives off secondary roots and buds, 
which lengthen to form flowering shoots. The structure of 
this root has been described by Drude (11), Kamienski (39), 
and Queva (62), The outer epidermal cells become completely 
filled with hyphae and fall off. The cortex consists of 8-10 
layers of cells that are much larger than the epidermal ones. 
The endodermis is composed of small cells with thickenings 
on the radial walls in the younger roots, but is indistinguishable 
in the older ones. The fibrovascular cylinder is composed 
mainly of thin-walled cells, there being only 3-4 patches of 
xylem (Kamienski). Material that the writer examined showed 



Monotropaceae with Reference to Ericaceae 63 

four small areas of xylem. These patches consist only of 1-3 
cells, generally reticulate tracheids, no vessels being present 
according to Kamienski. Drude reports the presence of spiral 
vessels. The writer has not seen any of the latter. Within 
the small circle formed by these four xylem elements occurs 
a parenchymatous mass of pith. Between and outside of the 
xylem patches is a comparatively large amount of phloem, 
composed of thin-walled cells, a few sieve tubes with slightly 
thick walls being present. These sieve tubes are described by 
Kamienski as having no true sieve plates, but that these are 
replaced by transverse partitions, and that the walls are thin 
at certain points. They are easily distinguished by their more 
granular contents. Secondary thickening occurs; Kamienski 
states that no cambium is present, and that the secondary 
tracheids are disposed either singly or in groups toward the 
pith or sometimes away from the pith. The phloem also grad- 
ually increases in the number of cells, until they join to form a 
ring around the wood. Queva (62), on the other hand, de- 
scribes the secondary wood as being formed only in a centrif- 
ugal direction — outside of the primary tracheids — and that 
after this, cambial arcs form and produce a continuous ring of 
xylem and phloem. Older roots examined by the writer showed 
an increase in the number of xylem elements and between the 
xylem and the phloem a layer of thin-walled cells resembling 
a cambium. The roots were not old enough to show the con- 
tinuous ring of xylem and phloem described by Queva. 

No complete description of the old root of M. uniflora has 
been found by the writer. The epidermal cells become filled 
with hyphae, but do not appear to drop off as soon as in M. 
hypopitys. The mycelial sheath still surrounds the oldest part 
of the root. The fibrovascular cylinder has a very irregular 
distribution of elements. The 3-4 single tracheids in young 
roots have increased in number, until there is quite a large area 
of wood, mostly reticulated tracheids. The secondary growth 
in thickness, from the material examined, seems to occur in 
the manner described by Queva for M. hypopitys. 

In the least saprophytic ones the epidermis soon dies and 
falls off, carrying with it the fungal hyphae as in Chimaphila 
and Pyrola. In Monotropa and especially M. uniflora the 
epidermis is still living and filled with hyphae when the root 



64 Henderson — Comparative Study of Pyrolaceae and 

is quite old. The less saprophytic ones have a fair amount 
of wood developed and a comparatively small amount of phloem 
as seen in Chimaphila and Pyrola. In Sar codes, Pterospora, 
and Monotropa the wood is less developed, the amount of phloem 
being considerably greater. This greater production of phloem 
and reduction in the amount of wood is characteristic of sapro- 
phytic plants. 

The Rhizome 

Transverse and longitudinal sections of the underground 
rhizome of Chimaphila umhellata were examined. On the ex- 
terior is an epidermis composed of somewhat rectangular cells 
(on transverse section) with rounded angles and thick walls. 
The outer wall is much thicker than the others and has on its 
exterior a layer of ridged cuticle. Interior to this is the cor- 
tex, composed of 7-9 layers of rounded thin-walled cells. The 
walls of the outer two layers of the cortex and those of the 
epidermis become thickened, forming a cork-like region, so 
that in cutting sections these all split off together. The cor- 
tical cells gradually increase in size toward the interior. The 
innermost layer, the endodermis, is composed of narrow rect- 
angular, but somewhat irregular, cells. These are thin-walled 
and show in section four to five cells filled with tannin. Internal 
to this is the fibrovascular system with an external small area of 
phloem and much larger area of wood. The pitted vessels ap- 
pear square on transverse section and there are numerous uni- 
seriate medullary rays through the wood. In C. umhellata there 
were found as many as four annual rings, an evidence that the 
rhizome is perennial. Inside the wood is a cylinder of rounded 
thin-walled cells, the pith ; starch grains occurring as either single 
or aggregate clusters are numerous in the epidermis, cortex, 
and pith. 

The structure of the rhizomes of C. maculata, P. rotundifolia, 
P. elliptica is very similar to that of C. umbellata. Conglomer- 
ate crystals are present in P. rotundifolia and P. elliptica but 
absent in C. umhellata and C. maculata. There is no rhizome 
in Mo7ieses uniflora or Monotropa. 

The Ascending Axis 
Transverse sections of all the species of Pyrolaceae and Mono- 
tropaceae investigated were taken at the base of the ascending 
axis just below the lowest set of scale leaves. 



Monotropaceae with Reference to Ericaceae 65 

In Chimaphila umhellata, the outline of the section is rounded 
pentagonal. The epidermis is papillate, the cells having a 
thick cuticle covered with wax. The epidermal cells and four 
layers of the cortex beneath have rather heavy thickened walls, 
so that this appears as a corky tissue. Inside this region are 
about four more layers of rounded, thin-walled cortical cells, 
and then the endodermis, a layer of narrow rectangular cells 
with the radial walls thickened. Within this is a narrow zone 
of phloem and a much wider one of wood. The material exam- 
ined shows three annual rings. There are five groups of primary 
bundles toward the interior. Innermost is the pith composed 
of thin-walled rounded cells. These cells and those of the 
cortex contain numerous conglomerate cr>'stals and aggregate 
starch grains. 

In C. maculata, the sections resemble closely those of C. 
umbellata, except that the outline is rounded triangular; there 
are not as many thick- walled layers of cortex; there are only 
three groups of primary bundles present; and crystals are not 
as numerous as in C. umhellata. 

In P. rotundifolia, the outline is rounded triangular; the 
epidermis is not papillate, the cells being only slightly curved 
outward; only the two outer layers of the cortex are thickened; 
there are 7-9 layers of unmodified cortex; crystals appear to 
be present in the cortex only. There are no distinguishable 
groups of primary bundles; otherwise the section appears like 
that of C. umhellata. 

In P. elliptica, the structure is almost exactly similar to that 
of P. rotundifolia. 

The axis of Moneses unifiora is not as thick and woody as 
those preceding. The outline is circular. The epidermal cells 
are only slightly curved outward. They and the outermost 
layer of the cortex are only slightly thickened but not nearly 
as much as in Pyrola and Chimaphila. There are about six 
layers of cortex in all. The endodermis resembles those of 
the preceding. There is a small amount of phloem, one year's 
growth of wood with four groups of primary bundles toward the 
interior, and a small area of pith. Single and aggregate starch 
grains are found in the cortex and pith, but there appear to be 
no crystals present. 

The structure in Monotropa hypopitys is greatly simplified. 
The section is circular and wider in diameter than in any of the 



66 Henderson — Comparative Study of Pyrolaceae and 

preceding, as in Monotropa the axis becomes fleshy. The epi- 
dermal cells are not papillate, and have a cuticular and waxy 
covering which is not as thick as in Chimaphila. There is no 
outer thick-walled area of cortex. It is composed of about 
ten rows of large thin-walled hexagonal cells, some of which 
have slightly thickened walls and contain tannin. The inner- 
most layer of the cortex consists of narrow elongated cells — 
the endodermis. The central vascular cylinder consists of 
several bundles separated from each other by medullary rays. 
Each consists externally of a wide patch of phloem — equal in 
width to that of the wood. The wood consists of 10-15 cells 
in each group. Those according to Kamienski (39) are tracheids 
with either spiral or annular thickening. This ring of wood 
consists of both primary and secondary wood. 

The structure in M. uniflora is exactly similar to that of 
M. hypopitys. 

Sections of the base of the ascending axis of Pleuricospora 
fimhriolata were taken from boiled up herbarium material. The 
cortex is wider than in Monotropa. The vascular cylinder is 
more united than in the others, there being a continuous ring 
of phloem and an almost solid interior of wood — the pith being 
very small in amount. The wood is much greater in amount 
than in Monotropa. 

Epidermis 

The epidermis was examined at the middle of the ascending 
axis or flowerstalk. In C. umhellata, it is composed of rect- 
angular cells with thick walls and with an exterior covering 
of ridged cuticle. Chloroplasts occur in the cells. Small 
papillae, also with ridged cuticle, are present on some of the 
cells. Stomata are present, but not numerous. They are 
small and appear normal and functional; some are of the nor- 
mal type with the slit parallel to the longitudinal axis — others 
show all stages of twisting of the guard cells until the opening 
between them becomes exactly transverse. The series is the 
same as in M. uniflora except that in the latter the guard cells 
are greatly enlarged and distorted. These transverse stomata 
are present on the stems of Viscum album, Arceuthobium, Anti- 
daphne, Loranthus, Lepidoceras, Nuytsia of the Loranthaceae; 
Choretriim, Mida, Myoschiliis, Anthobolus, Santalum album. 



Monotropaceae with Reference to Ericaceae 67 

Thesium of the Santalaceae; Cassytha of the Lauraceae; Sali- 
cornia, Casuarina, Staphylea pinnata. The first three groups 
are all, with the exception of Nuytsia, parasitic, so that the 
presence of transverse stomata on the stem may indicate an 
abnormal system of nutrition. 

In C maculata the epidermis is almost exactly similar to that 
of C. umbellata, except that the papillae seem slightly longer 
and have somewhat thicker walls. 

In P. rotundifolia the epidermal cells are longer and thinner 
walled; there are no papillae; stomata are more numerous and 
are mostly of the longitudinal slit type. 

The epidermis of P. elliptica is similar to that of P. rotundi- 
folia, except that stomata are very rare and in all pieces of 
epidermis examined were of the longitudinal type. 

In Moneses uniflora there are papillae present as in Chima- 
phila. The epidermal cells are long, narrow, and thin-walled, 
and contain chloroplasts as in the preceding. In all the mate- 
rial examined the writer found no stomata present. 

In Sarcodes sanguinea the epidermal cells are also long, nar- 
row, and thin-walled. Oliver states that no stomata are present 
on the flower stalk (the ascending axis), but the writer finds 
that, though rare and somewhat distorted, stomata are un- 
doubtedly present. Simple stomata with a longitudinal slit as 
in M. hypopitys (Fig. 4, 4) occur. Others have the guard cells 
twisted around so that the slit is diagonal (Fig. 4, 2). Others 
are remarkable in that they have three guard cells (Fig. 4, 3), 
At the base of the axis a few glandular hairs are present. These 
increase in number toward the top of the flower stalk. They 
are multicellular with a thick stalk and a slightly rounded head. 

In Pterospora andromedea the epidermal cells are similar to 
those of Sarcodes. This is the only member of the Monotro- 
paceae up to the present that has been described as possessing 
stomata on the flower stalks. MacDougal (48), p. 38, states 
"Pterospora is the only dicotyledonous plant without chloro- 
phyll beside Cotylanthera that is furnished with stomata." 
These stomata are of the normal type with the slit parallel 
to the longitudinal axis. They are very rare. Hairs of two 
types occur on the flowerstalk; simple uniseriate hairs com- 
posed of 3-4 elongated cells the last one club-shaped; glandular 
hairs with a multicellular stalk and a multicellular club-shaped 
head. 



68 Henderson — Comparative Study of Pyrolaceae and 



In Monotropa hypopitys, the epidermal cells are similar to 
those preceding. Stomata are present though rather rare. 
Previous investigators are unanimous in saying that stomata 
are absent on the flowerstalk (9. 48, 73). The writer finds 
two types of stoma — the normal type with the slit parallel 
to the longitudinal axis (Fig. 4, 4) and that with the slit trans- 
verse to the longitudinal axis (Fig. 4, 5). The first type is 




Fig. 4. Stomata X 290. 

I. On lower epidermis scale of Monotropa uniflora 
2-10. On epidermis of ascending axis of: 
2-3. Sarcodes sanguinea 
4-5. Monotropa hypopitys 
6-10. M. uniflora 

more frequent in M. hypopitys. The guard cells are extremely 
large and often much distorted. Whether or not these stomata 
function one cannot say, but their presence indicates that they 
were functional at one time, at least when the plant was young 
and before the guard cells were pulled apart by the rapid upward 
growth of the flowerstalk. Unicellular hairs with ridged cuticu- 
lar thickenings are present on the epidermis. 



Monotropaceae with Reference to Ericaceae 



69 



In M. nniflora the epidermal cells are similar to those of 
M. hypopitys. The transverse type of stoma is much more 
frequent, the longitudinal type being rather rare. Fig. 4, 6-10 
shows a series in the formation of a transverse stoma from the 
longitudinal. 6 is a normal stoma. In the growth of the stalk 
the guard cells gradually become pulled apart and slightly 
turned around as in 7. In 8 the slit is diagonal, 9 shows 
the cells almost completely around, and finally 10 shows the 
directly transverse slit. 

Portions of the epidermis of boiled-up material of Pleuri- 
cospora were found to have shorter thicker walled cells than the 
preceding. No hairs or stomata have as yet been seen but the 
material at hand was limited, so this does not finally preclude 
the possibility of their occurrence. Hairs similar to those found 
on the axis in Pyrolaceae and Monotropaceae are characteristic 
of many of the Ericaceae. This is another close similarity 
found in the three families. 





Fig- 5- Transverse section of ascending axis, showing sector of fibrovas- 
cular system X 200. 

1. Chimaphila umbellata 

2. Pleuricospora fimbriolata 

X = xylem; P = phloem; HB = hard bast; C = cortex. 

Transverse sections of the ascending axis were taken at a 
point half way between the flower or flowers and the leaves, 
or in the Monotropaceae half way between the flowers and the 
base of the ascending axis. 

In C. umbellata the epidermis appears as a hollow cylinder of 
oval cells with a thick outer cuticle and covering of wax. The 



70 Henderson — Comparative Study of Pyrolaceae and 

papillate hairs appear on transverse section. Internal to the 
epidermis are two to three layers of thick-walled, then two to 
three layers of thin-walled, cells forming the cortex. The 
outer 3-4 layers of the phloem are heavily lignified forming an 
area equal in width to the succeeding area of thin-walled phloem. 
There is only one year's wood developed, but this is rather 
large in amount (Fig. 5, i), the entire area being one and a half 
times in width that of soft and hard bast together. Internal 
to the wood is a rather large area of pith composed of thin- 
walled rounded cells with small intercellular spaces. 

In C maculata the epidermal papillae appear more numerous 
and more strongly developed than in C. umhellata. There is 
an outer thick-walled area of three layers and an inner thin- 
walled area of 3-4 layers of cortex. There are four layers of 
thick-walled hard bast which is slightly greater in width than 
the soft bast. The wood is not as strongly developed as in 
C. umhellata, the width being equal to that of the soft and 
hard bast combined. The pith is similar to that of C. um- 
hellata. 

In P. rotundifolia the epidermis is not papillate. There are 
two layers of thick-walled, three of thin-walled, cortical cells. 
The hard bast is five layers in thickness, being much greater 
in width than that of the soft bast. The wood is developed 
about as much as in C. maculata, being equal in amount to the 
width of the hard and soft bast together. 

In P. elliptica the appearance of the section is very similar 
to that of P. rotundifolia. 

In Moneses uniflora the epidermis is not papillate. All the 
cortical layers (5-6) are thin-walled. There are four to five 
layers of hard bast that dip in slightly between the patches of 
soft bast so that the latter does not form a continuous ring 
as in all the preceding. Each patch consists only of a few 
small thin-walled cells. Internal to these is a ring of wood 
that is very poorly developed in comparison with all those 
preceding. In width it is only slightly greater than that of 
the soft bast patches. 

In Monotropa hypopitys the axis becomes more fleshy and 
wider in diameter than in any of the preceding. There are 
papillate hairs present that are more numerous and much longer 
than in Chimaphila. Internal to the epidermis are about twenty 



Monotropaceae "with Reference to Ericaceae 



71 




HB 



Fig. 6. T. S. ascending axis Pterospora andromedea X 200. 



72 Henderson — Comparative Study of Pyrolaceae and 

layers of rounded thin-walled cortical cells. There is a very- 
great development of hard bast (about 8-9 layers) which dips 
in between the numerous phloem patches and joins with the 
indurated medullary rays. It is greater in width than the soft 
bast, which is well developed in this species. The latter has 
a width about twice that of the wood, which is extremely re- 
duced in amount, there being only about five to eight cells in 
a group interior to the many celled phloem patch. 

The structure in M. uniflora (Fig. 7) resembles that of M. 
hypopitys except that no hairs are present on the epidermis, 
and the amount of hard bast is not as great, there being only 
about 4-5 layers. 



»^----H8 



Fig. 7. T. S. ascending axis Monotropa uniflora X 200. 
L = lignified pith. 

MacDougal (48) describes the structure of the ascending axis 
of Pterospora andromedea as follows: "The epidermis is com- 
posed of elongated spindle-form elements. The epidermis and 
the two underlying layers are slightly lignified. The outline 
is exceedingly crooked, and shows deep invaginations directly 
over large air-chambers, while in other places distinct fixed 
stomata are to be found. The cortex is composed of cylindrical 
elements arranged in circles with intercellular spaces which 
increase in size outwardly. The fibrovascular bundles contain 
one or two annular and two or three spiral vessels, with a few 
alongated elements of slight differentiation, which are perhaps 



Monotropaceae with Reference to Ericaceae 73 

tracheides. A number of closed sieve tubes are present. The 
xylem bundles do not form a ring, but immediately external to 
the bast-region is a complete cylinder of heavy sclerenchyma 
composed of ten to fifteen layers of cells. Both the xylem and 
the sclerenchyma are distinctly lignified. The medulla is from 
3 to 6 mm. in diameter, making up about half of the cross sec- 
tion of the stem, and is composed of cylindrical elements with 
ample intercellular spaces." In the material examined by the 
writer (Fig. 6) the hard bast area was found to be composed of 
even more than fifteen layers of cells. The phloem was found 
to be greater in width than the xylem. The xylem in Pterospora 
is better developed, i. e., has more cells and more heavily thick- 
ened walls, than in Monotropa, but is less so than in Pleuri- 
cospora. 

Sections of the axis of Pleuricospora fimbriolata were taken 
from a boiled-up herbarium specimen. The axis is wider than 
in Monotropa, about the same thickness as in Pterospora, and 
consists mainly of cortex and pith composed of rounded thin- 
walled cells. The vascular system (Fig. 5, 2) forms an irregular 
ring placed nearer the exterior than the center of the section. 
No hard bast is present; the area of soft bast is about equal 
to that of the wood which is better developed than in any other 
members of the Monotropaceae examined, there being more 
cells and the walls more heavily thickened. 

According to Solereder (73), the axis of Schweinitzia odorata 
resembles that of Sarcodes and Pleuricospora in that it does 
not possess a ring of hard bast fibers. 

Sections of the axis of Sarcodes sanguinea were cut some 
distance below the middle. They showed a great increase in 
size over any of the others examined. The main bulk of the 
axis is made up of thin-walled cells of the cortex and pith. The 
bundles as in Pleuricospora form an irregular ring which in 
position is nearer the exterior than the center. There is no 
hard bast produced in Sarcodes. In the section examined by 
the writer, the phloem was about equal in width to the xylem. 
The phloem forms a continuous ring; the groups of xylem being 
separated from each other by medullary rays. Oliver (58), 
Fig. 49, figures three of these bundles. At the level where he 
examined it, the phloem is less in extent than the xylem. He 
states that the bundles undergo no secondary thickening. 



74 Henderson — Comparative Study of Pyrolaceae and 

In comparing Monotropa, Pterospora, Pleuricospora, and Sar- 
codes, these have been considered in order according to their 
relative fleshiness and size. The series, given in order of their 
relative structure from the least simplified to the most simpli- 
fied, taking as a basis of comparison the relative amount of 
phloem and wood produced, would be Pleuricospora, with a 
continuous ring of well developed wood equal in width to the 
phloem, Sarcodes and Pterospora, with the wood not continuous 
and not so strongly developed but equal in width to the phloem, 
then Monotropa, with the wood only present in small patches 
of about five to eight cells in a group and the phloem very well 
developed. 

Sections of the axes of the youngest shoots of some typical 
ericaceous plants were examined. These resemble closely 
those of Chimaphila and Pyrola. In Ledum groenlandicum, 
Gaultheria procumbens. Rhododendron lapponicum, the epidermis 
and one to two outer layers of the cortex are thickened just as 
in Chimaphila and Pyrola. The inner cortex is less regular, 
there being wider and more irregular intercellular spaces than 
in Chimaphila and Pyrola. There is a ring of hard bast present 
as in nearly all the Pyrolaceae and Monotropaceae. The wood 
is generally wider than in Chimaphila. The pith is slightly 
different, there being present trabeculae of thicker walled cells. 
No comparison can be made between Chimaphila and Pyrola 
on the one hand, and older sections of ericaceous plants, as 
none of the former lives over four years and many of the latter 
live for many years becoming very woody. 

As regards the structure of the epidermis, cortex and the 
development of cork tissue there is a complete series from 
shrubby Ericaceae to the most simplified soft fleshy t>'pes of 
Monotropaceae. In Rhododendron lapponicum no cork cam- 
bium is developed until the third or fourth year when one de- 
velops out of phloem tissue. This origin of the cork cambium 
has been reported by Vesque (82). Layers of cork are laid 
down and all of the external cortex and epidermis fall off. In 
the more woody Pyrolaceae, Chimaphila and Pyrola, there is a 
tendency for the outer thicker-walled layers of the cortex to 
separate from the rest during the second and following years. 
As the plant only lives for 3-4 years no opportunity for the 
formation of a cork cambium takes place. In the saprophytes 



Monotropaceae with Reference to Ericaceae 75 

which live above ground only one season, there is no separa- 
tion of the cortex even suggested. Pterospora is reported by 
MacDougal to have the epidermis and the two outer layers of 
the cortex slightly lignified, but in the others the cells are not 
at all thickened. 

The structure of the axis also illustrates a gradual descend- 
ing series from typical Ericaceae, with strong development of 
wood, to Chimaphila, which is almost as woody as some of the 
sub-shrubby Ericaceae, to Pyrola, which is less woody, to Mon- 
eses, with still less wood developed, then v.dth a still decreasing 
amount of wood development through Pleuricospora, Sarcodes, 
Pterospora, and finally to Monotropa, where the wood is ex- 
tremely small in quantity and the phloem well developed. 

The Leaf 

In C. umbellata the stem produces above ground alternating 
groups of 2-3 scale leaves and whorls of 3-5 foliage leaves. 
The leaves persist for four years. The last whorl of leaves 
and the inflorescence appear in the same year so that no scale 
leaves occur between the youngest whorl of leaves and the 
inflorescence. The leaves are leathery, somewhat narrow at 
the base, becoming wider above with a serrate margin, dark 
green above, lighter below. 

In C. maculata, there is the same alternating arrangement 
of scales and leaves as in C. umhellata, except that only three or 
four foliage leaves are produced in a whorl. The inflorescence 
does not appear in the same year as the last whorl of leaves as in 
C. umhellata, so that above these at the base of the flowers talk 
three scales are borne. These are the scales which protected 
the inflorescence over the preceding winter. The leaves are 
leathery, lanceolate, with an acute apex, serrate, dark green 
above (though lighter than in C. umhellata), with white spots 
especially along its midrib, and rather reddish green beneath. 

In P. rotundifolia, the arrangement of scales and leaves is 
like that in Chimaphila, except that one to three foliage leaves 
may be produced in one year, and that these are not arranged 
in a whorl as in Chimaphila. The leaves are evergreen, lasting 
from two to four years, and the node between two successive 
years leaves is short, so that the leaves of two to three years 
appear to be in a common rosette. They have long, narrowly 



76 Henderson — Comparative Study of Pyrolaceae and 

winged petioles, and large orbicular crenulate, prominently 
veined, dark green, leathery blades. 

In P. elliptica, there occurs the same succession of scale 
leaves and foliage leaves, ending with three scale leaves at 
the base of the flowerstalk, this arrangement being character- 
istic of the genus. The leaves are evergreen, lasting from two 
to three years. They have narrowly winged petioles, shorter 
than in P. rotundifoUa, and large elliptic crenulate blades, which 
are smaller in size, less prominently veined, lighter green, and 
less leathery than in P. rotundifoUa. 

In P. secunda, the leaves are evergreen and smaller than in 
P. elliptica. The petioles are shorter, the blades much less 
leathery, and lighter green in color. 

In P. minor, the leaves are evergreen and of the same size, 
or smaller than in P. secunda. 

In P. chlorantha, the leaves are evergreen and of the same 
size or smaller than in P. minor. 

In P. aphylla Holm (30) has described and figured a rosette 
of small green leaves "provided with a distinct petiole and 
a blade varying from lanceolate to broadly ovate, obtuse or 
slightly pointed." Below these occur a few scale leaves, and 
above them the bud for the next year's inflorescence. The 
green leaves are deciduous and are produced in alternate years 
with the flowering shoot. For this reason some have incor- 
rectly described the plant as aphyllous. Lateral inflorescences, 
which arise in the axil of a scale, occur, and are therefore not 
preceded by green leaves. 

In Moneses unifiora, the arrangement of alternating whorls 
of scales and leaves is similar to that of the genus Pyrola. The 
leaves, though not at all leathery, are evergreen for two to 
three years. They are small elliptic, acute, with a serrate margin. 

In Pterospora andromedea, the leaves are reduced to brown- 
ish scales arranged closely together, in fact overlapping at the 
base of the flowering axis, but becoming more distant from 
each other toward the region where flowers are produced. Those 
at the base of the stem are small and somewhat triangular. 
Further up the axis, these become narrower and longer, and 
finally they decrease in size toward the flowers. Those at the 
base are smooth on the outer (lower) surface, but toward the 
top of the flower axis they become more and more hairy gland- 



Monotropaceae with Reference to Ericaceae 77 

ular. Stalked glandular hairs occur on the margins of all 
scales. 

In Sarcodes sanguinea, the leaves, as described by Oliver (58), 
"show a gradual transition in form from the small scales at the 
base to the thick fieshy ones covering the greater part of the 
vegetative portion of the shoot. These again pass over into 
the linear bracts. The leaves and bracts are fringed with 
stalked glands." The outer surfaces of the leaves toward the 
base of the flower stalks are smooth ; toward the tip they become 
slightly pubescent, the flower bracts becoming quite markedly 
pubescent. All the leaves and bracts are crimson in color. 

In Monotropa hypopitys, the leaves are reduced to small oval- 
triangular, somewhat thick, yellow, slightly puberulent scales, 
pressed tightly against the flowering axis. They are arranged 
closely together at the base of the flower axis, but become 
separated further up. 

In M. uniflora, the leaves are like those of M. hypopitys, 
except that they are white and glabrous and much more mem- 
branous. 

In Pleuricospora fimbriolata, the leaves are likewise reduced 
to pale brownish scales that are small, imbricating at the base, 
but become larger and more distant from each other above. 
They all have hair-like processes on their margins, resembling 
somewhat an incompletely developed stalked gland of Sarcodes. 

This reduction of leaves to scales and the general arrangement 
of these are similar in Allotropa, Schweinitzia, and Newberrya. 

In typical Ericaceae, as in the Pyrolaceae, there is produced, 
after the foliage leaves of one year, a leaf or flower bud covered 
with bud scales. This gives the alternating series of scale 
leaves and foliage leaves seen in the Pyrolaceae. In the Eric- 
aceae the scales are deciduous, falling olif shortly after the leaves 
unfold. In the Pyrolaceae, they are persistent and green, or 
greenish membranous for the season, then becoming brownish 
and lasting for 2-4 years. This persistence of the scales through 
the season also occurs in all members of the Monotropaceae. 
Here they are enlarged and take the place of foliage leaves. 

In Ericaceae the foliage leaves are always green and usually 
quite leathery, in most also evergreen for two or more years. 
The genus Chimaphila and some of the Pyrolas, i. e., P. rotundi- 
folia, are also evergreen and leathery, but in other species of 



78 Henderson — Comparative Study of Pyrolaceae and 

Pyrola the leaves become less leathery until in P. {Moneses) uni- 
flora the leaf has a characteristic deciduous structure but is still 
evergreen. In P. aphylla, the foliage leaves are deciduous, and 
the ascending axis, which bears the flower, produces only scale 
leaves along its course. This species is a connecting link be- 
tween the evergreen type and that of all the members of the 
Monotropaceae, where no foliage leaves are produced, their 
place being taken by expanded fleshy scale leaves. 

The question arises as to whether the scale leaves in the 
Monotropaceae are the homologues of the scale leaves, or of the 
foliage leaves in Ericaceae and Pyrolaceae. In the writer's 
opinion, they represent both scale leaves and foliage leaves. 
The deciduous scale leaves of the Ericaceae have gradually 
become green and persistent, then expanded, enlarged and much 
more numerous. The green leaves have become smaller and 
all have changed in color from green in the Ericaceae and Pyrol- 
aceae to brownish in Pterospora, crimson in Sarcodes, pinkish 
yellow to yellow in M. hypopitys, to pinkish white or white in 
Monotropa. 

The Leaf — Microscopic Structure 

The microscopic structure of the leaf of C. umhellata has been 
described and figured by H. E. Petersen (60). His material 
was collected in Denmark, but corresponds according to his 
description and figures almost exactly with the material exam- 
ined by the writer. The epidermis, both upper and lower, is 
heavily cuticularized, and, on the surface of this, a layer of wax 
is present. (The latter is not mentioned by Petersen.) The 
epidermal cells are rectangular on transverse section, wavy 
walled on surface view. There is a three-layered palisade tissue 
beneath this, and a spongy mesophyll composed of thin-walled, 
branched cells with large intercellular spaces. Stomata are 
present on the lower epidermis on the same level as the other 
epidermal cells. Petersen reports the presence of starch in 
both the upper and lower epidermis, and the absence of hairs 
and hydathodes. Starch is very plentiful in both palisade and 
spongy mesophyll, though he does not make note of this. He 
also does not mention the presence of conglomerate crystals of 
calcium oxalate, which the writer finds occur in large numbers 
throughout the spongy mesophyll. These occur as small con- 



Motwtropaceae with Reference to Ericaceae 79 

glomerate crystals, about one-third the size of a normal mesophyll 
cell, and as much larger masses, completely filling an enlarged 
mesophyll cell. They are mentioned by Rommel (65) who has 
also given a short description of the microscopic structure of 
the leaf similar to Petersen. Both of these descriptions, how- 
ever, deal with only the laminar portion of the leaf. 

At the midrib, the halves of the lamina form an angle of 90°, 
and the leaf extends out into a ridge. The upper epidermis is 
similar to that over the lamina, consisting of rectangular cells (on 
transverse section) with thickly cuticularized walls, especially 
on the outer surface. Beneath the upper epidermis, the palisade 
tissue thins out to only one layer of cells, that are almost iso- 
diametric. Immediately below this is the midrib vascular 
bundle. Within the bundle sheath is a fan-shaped area of 
x\'lem, below which is a narrower region of phloem, composed 
of a narrow area of soft, and a wider area of hard, bast. Be- 
neath the bundle are two layers of spongy parenchyma cells, 
which are round, somewhat thick-walled, and closely packed 
together. Next to this is one layer of rounded cells, pressed 
tightly against the lower epidermis. The walls are rather 
heavily thickened, so that in cutting they easily break away 
from the rest of the spongy mesophyll. The lower epidermal 
cells, at the midrib region, become less rectangular, more iso- 
diametric than in the laminar portion, the cuticle of each cell 
swelling out somewhat, so that the outline of the lower epidermis 
in transverse section becomes crenulate. 

C. maculata, while showing essentially the same type of leaf 
as C. umbellata, differs slightly in structure. The upper epi- 
dermis consists of wavy walled cells, in surface section, appear- 
ing rectangular in transverse section, except that the outer 
face of each cell protrudes from the surface forming a short 
rounded papilla. This is, however, confined to the upper epi- 
dermis, the cuticle of the lower being perfectly fiat as in C. 
umbellata. Chloroplasts occur in both upper and lower epi- 
dermis, no hairs are present, and stomata, similar in form to 
those of C. umbellata, but projecting slightly from the epidermis, 
occur on the lower surface. The palisade tissue consists of 
but two layers of elongated cells. The spongy mesophyll has 
several layers of irregularly branching cells with large inter- 
cellular spaces. Both palisade and spongy mesophyll cells are 



8o Henderson — Comparative Study of Pyrolaceae and 

filled with starch grains; small and large conglomerate crystals 
of calcium oxalate, exactly similar to those of C. nmbellata, 
occur in the spongy mesophyll. 

At the midrib the laminar halves form an angle of 135°- 
180°, the leaves being almost entirely flat, but with a ridge 
on the lower epidermis, similar to that of C. timhellata. The 
upper epidermis is of the same appearance as that over the 
lamina. The palisade still consists of two layers, but the cells 
are shorter and wider. Beneath this are one to two layers of 
spongy mesophyll. The midrib bundle is very similar in ap- 
pearance to that of C. umbellata. Under the bundle are three 
layers of spongy mesophyll cells, closely packed together and 
with slightly thickened walls similar to those of C. umbellata, 
as is also the layer just next to the lower epidermis, with its 
rounded thick-walled cells, closely packed together and pressed 
against the lower epidermis. The cells of the latter have be- 
come shorter, more isodiametric, and have their outer walls 
curved outward slightly. 

The microscopic structure of the leaf of P. rotundifolia has 
been described by Rommel (65), and of P. rotundifolia var. 
grandiflora by Petersen (60). The material examined corre- 
sponds fairly well with both of these descriptions except that 
the writer finds stomata, not hydathodes, on the upper epi- 
dermis; chlorophyll grains in the upper epidermal cells; crystals, 
both small and large, in the mesophyll (Petersen does not 
mention them, and Rommel states that they are absent); and 
no differentiation into palisade and spongy mesophyll. The 
epidermis is covered by a thin cuticle (much less than in Chima- 
phila) and a layer of wax. Both upper and lower epidermis 
consist of wavy-walled cells on surface section, rectangular in 
transverse section, and contain chloroplasts. Numerous sto- 
mata are present on the lower epidermis, projecting slightly 
from the level of the other epidermal cells. They are fairly 
frequent on the upper epidermis, especially toward the margin 
of the leaf. The mesophyll consists of five to six layers of 
closely packed thin-walled cells. Rommel describes the meso- 
phyll as having smaller intercellular spaces near the upper 
epidermis, and larger intercellular spaces near the lower epi- 
dermis. Petersen's figure (p. 81) also illustrates this, but the 
writer's material shows no difference between the upper and 



Monotropaceae with Reference to Ericaceae 8i 

lower mesophyll. There is, however, the distinct transparent 
median non-tannin-containing layer of the mesophyll described 
by Petersen for his Danish specimens of P. rotundifolia. The 
mesophyll cells, beside containing starch and tannin, contain 
crystals similar to those of Chimaphila. At the midrib, the 
leaf becomes prominently ridged on both surfaces. The upper 
epidermal cells become enlarged and have a much thicker layer 
of cuticle and wax than over the rest of the lamina. The first 
layer of mesophyll cells become packed closely together and 
against the upper epidermis. There are four to five layers of 
rounded thin-walled cells, above and below the midrib bundle. 
The latter closely resembles that of Chimaphila. The lower- 
most layer of mesophyll also consists of rounded, thick-walled, 
closely packed cells, tightly pressed against the lower epidermis. 
The latter has its cells enlarged and has a thicker cuticle than 
on the laminar region. 

In P. elliptica, the structure of the lamina is exactly similar 
to that of P. rotundifolia, except that the cuticle with its cover- 
ing of wax is much thinner and that on the upper epidermis 
is slightly thicker than that on the lower epidermis. At the 
midrib, the structure is again like that of P. rotundifolia, except 
that the cuticle is thinner. 

The structure of the leaf of P. secunda has been described 
by Petersen and Rommel and figured by the former, p. 85. 
The type of leaf is very similar to that of P. rotundifolia — 
there is no dififerentiation into a palisade and a spongy meso- 
phyll. The cuticle, according to Petersen, is thicker than in 
P. rotundifolia (this is not true of the writer's material) and 
stomata are present also on the upper epidermis. Rommel 
fails to note the latter, and also states that no crystals are pres- 
ent. At the midrib, the leaf is ridged above, but not as much 
as in P. rotundifolia. 

The structure of the leaves of P. media and P. picta has been 
described by Rommel. These are similar to P. rotundifolia 
for there is no palisade mesophyll. He states that crystals 
are absent in these. 

The leaf of P. minor has been described and figured (p. 83) 
by Petersen as having an undifferentiated mesophyll like P. 
rotundifolia, but Rommel states that there is one layer of palisade 
tissue. The writer finds the structure of the leaf to be similar 



82 Henderson — Comparative Study of Pyrolaceae and 

to that of P. rotundijolia — no palisade tissue being present. 
In some places, however, a few of the cells of the layer next 
to the upper epidermis become slightly elongated, as if a palisade 
was beginning to form, or rather as if these were the few remain- 
ing cells of what was once a palisade layer. Rommel notes the 
presence of crystals. Petersen mentions the presence of stomata 
on the upper epidermis, a fact not stated by Rommel. The 
writer finds stomata on both upper and lower epidermis, pro- 
truding slightly from the level of the epidermis. At the midrib 
the leaf is ridged above and below, but even less than in P. 
secunda. The bundle is not as strongly developed as in P. 
rottmdifolia. 

In P. cJilorantha, Rommel states that there is one layer of 
palisade mesophyll, and that crystals are present. The writer's 
material agrees with this. The epidermal cells are wavy-walled 
on surface view, rectangular in transverse section. Stomata 
are present on the lower surface only. There are one layer of 
palisade and four layers of spongy mesophyll with larger inter- 
cellular spaces than in P. rotundifolia. At the midrib there is 
only a slight curving upward and a small downward ridge. 
The bundle is similar to that of P. minor. 

In P. aphylla, Holm (30) describes the leaf as having a normal 
epidermis, covered by a thick and wrinkled cuticle, stomata are 
present on both upper and lower epidermis, but more numerous 
on the lower epidermis. He reports the presence of two layers 
of palisade tissue and a spongy mesophyll of loosely connected 
cells with large intercellular spaces. 

In the genus Pyrola, most of the species examined, i.e., P. 
elliptica, P. secunda, P. media, P. picta, conform to the type 
of P. rotundifolia with non-differentiated mesophyll. P. minor 
seems to show a transition toward the formation of a palisade. 
P. chlorantha shows one layer of palisade tissue, and P. aphylla 
shows two layers of palisade and a typical spongy mesophyll. 

The leaves of Motieses uniflora have also been described 
microscopically by Petersen and Rommel and figured by the 
former (p. 86). The epidermal cells — wavy-walled in surface 
section, rectangular in transverse section — have only slightly 
cuticularized outer walls and contain chlorophyll. Stomata 
are numerous on the lower epidermis, and are slightly project- 
ing. The upper layer of the mesophyll consists of slightly 



Monotropaceae with Reference to Ericaceae 83 

elongated cells forming a palisade of one layer. The spongy 
mesophyll cells branch irregularly and have large intercellular 
spaces. Starch occurs in all the mesophyll cells. Rommel 
does not mention the presence of the one layer of palisade tissue. 
He also states that crystals are not present, while the writer 
finds that they are present. At the midrib the upper surface 
of the leaf is curved slightly upward, the lower flat. Both 
upper and lower epidermis are similar in appearance to that 
over the lamina. The palisade cells become somewhat shorter. 
One layer of rounded mesophyll cells occurs between the palisade 
and the bundle. The midrib bundle is much smaller in extent 
than in either Chimaphila or Pyrola, the latter bundles being 
almost equal in size to the midrib. It consists of a small area 
of xylem — not radiating as in the others — beneath which are 
several layers of phloem. Beneath the bundle are two layers 
of spongy mesophyll cells between it and the epidermis. 

MacDougal (48) has described in part the structure of the 
leaf of Pterospora andromedea. He describes marginal stalked 
glands similar to those on the flowering axis. According to him 
"The basal scales are flecked with irregular patches of yellowish 
brown areas, due to the penetration of the epidermal cells by 
brownish hyphae, which completely fill them and extend over 
the surface of the scales in a network." In a few scales the 
writer has seen ramifying hyphae over the surface, but not 
penetrating the epidermal cells. The epidermis consists of 
elongated narrow cells that appear narrowly oval on transverse 
section. Stoma ta, though not numerous, are present on the 
lower epidermis. Hairs are present on the lower surface toward 
the sides of the scale. These are simple unicellular protuber- 
ances. The lowermost scales are smooth. Further up the 
stalk, the scales become more and more hairy until those sub- 
tending the flowers have long stalked glandular hairs similar 
to the marginal ones. These consist of a rather long multi- 
cellular stalk with an oval head composed of glandular cells. 
The mesophyll is composed of numerous layers of thin-walled 
hexagonal cells. The transverse section is wider at the mid- 
rib, the midrib bundle being larger than the others. There is 
a slight curving upward at the midrib region as in Moneses 
uniflora. The bundles are more reduced than in Moneses uni- 
flora. There are several xylem elements present, but the main 
part of the bundle consists of phloem. 



84 Henderson — Comparative Study of Pyrolaceae and 

The structure of the leaf of Sarcodes sanguinea, described 
by OHver (58), corresponds closely with the material examined 
by the writer. Stalked glands, similar in appearance to those 
on the flowering axis, appear on the margin of the leaves. The 
epidermis consists of thin-walled hexagonal cells slightly longer 
than broad. On transverse section, these appear as somewhat 
oval cells, those of the lower epidermis being slightly smaller 
than those of the upper. Both surfaces are covered with cuticle 
and a thin layer of wax, that on the outer or lower surface being 
slightly thicker than that on the upper. Stomata are absent. 
The basal leaves have a smooth lower epidermis, no hairs being 
present. Further up the flowering axis, the lower surface 
shows beginnings of multicellular glands with a long multi- 
cellular stalk and a club-shaped head. These become more 
numerous on the bracts which subtend the flowers. The meso- 
phyll is undifferentiated, except that the first layer of cells 
beneath the epidermis is composed of cells similar to it. Below 
this occur 17-18 layers of hexagonal, thin-walled, closely packed 
cells. The transverse section of the leaf is the same throughout, 
the bundles being all nearly equal in size. They are much 
more reduced than in Moneses uniflora. Several xylem vessels 
are present, but the main part of the bundle is made up of 
phloem. 

The structure of the leaves of Monotropa hypopitys has been 
described by Kamienski (39). The writer's material corre- 
sponds closely with his description, except for the presence of 
hairs, a fact which he does not mention. His material, however, 
may have been M. hypopitys var. glabra. The epidermis con- 
sists of narrow elongated cells on surface view, somewhat oval 
on transverse section, with the outer wall cuticularized, ridged, 
and with a thin layer of wax on the outside of the cuticle. Hairs 
are present, few on the upper, numerous on the lower epidermis. 
They are simple, unicellular outgrowths with small, wart-like 
protuberances. Stomata are absent on the upper and very rare 
on the lower epidermis. Solereder (73) mentions that they 
are rare on the lower surface of the leaf, but all other writers 
say they are absent. The writer found three to five on a scale. 
The mesophyll consists of several layers of thin-walled, hexagonal 
cells with no intercellular spaces. There is no difTerentiation 
into palisade and spongy mesophyll. Several bundles almost 



Monotropaceae with Reference to Ericaceae 85 

equal in size pass through the mesophyll so that at the midrib 
the scale is only slightly thicker than in the laminar region. 
The bundle is even more reduced in size and number of ele- 
ments than in Pterospora and Sarcodes, the woody tissue con- 
sisting only of one to two elements, the main part of the bundle 
being composed of phloem. 

The leaf of M. uniflora is exactly similar in structure to that 
of M. hypopitys except that no hairs are present in M. uniflora 
and stomata are even more rare than in M. hypopitys (Fig. 4, i). 
The writer found only one stoma on the lower epidermis of each 
leaf. 

The leaf of Pleuricospora fimbriolata is very similar in its 
structure to that of Monotropa. The epidermal cells are slightly 
longer than wide on surface view, and oval in transverse section. 
They are covered by a thin ridged cuticle and layer of wax. 
No hairs or stomata are present. There are eight rows, at the 
widest part, of thin-walled, closely packed hexagonal cells. 
The midrib bundle is only slightly larger than the others and is 
even more reduced than in Monotropa. 

From reviewing literature on the structure of the leaves of 
the Ericaceae (88, 56, 60, 73) and from an examination of sec- 
tions of the leaves of various members of the family, the writer 
finds that in general the structure is very similar to that of 
Chimaphila, which the writer considers to be the least sapro- 
phytic genus of the Pyrolaceae. The Ericaceae generally agree 
with Chimaphila in having a thick cuticle, often with a coating 
of wax, a mesophyll differentiated into palisade and spongy 
regions, and chlorophyll in the upper and lower epidermis. 
Solereder reports cuticular ridges as a common occurrence in 
the Ericaceae. Their presence has been indicated in all the 
Pyrolaceae and Monotropaceae examined. Papillae on the 
epidermis, except at the midrib, are rare in the Pyrolaceae and 
Monotropaceae, only occurring in C. maciilata. They are 
present, however, on the lower epidermis of Rhododendron 
campylocarpum, R. thomsoni, Kalmia glauca, K. latifolia. At 
the midrib in typical Ericaceae, the epidermal cells often bulge 
out to form papillae. This is true of Chimaphila and Pyrola 
also. 

Stomata in the Ericaceae and Pyrolaceae may be present on 
the lower surface only, but are frequently present on both sur- 



86 Henderson — Comparative Study of Pyrolaceae and 

faces. They do not, except in a few cases, have any specially 
formed subsidiary cells but according to Breitfeld (88) they often 
extend beyond the surface so that they overlap the surrounding 
epidermal cells to some extent. This arrangement is also true 
of those of the Pyrolaceae and Monotropaceae (Fig. 4). 

The types of hairs present in Ericaceae are varied; Breitfeld 
(88, p. 329, PI. VI), Neidenzu (56, p. 141, Pis. Ill, IV, V, 
VI), and Solereder (73, p. 484, 485) have given detailed de- 
scriptions and numerous figures of those found in all groups 
of the Ericaceae. The forms of hairs present in the Pyrolaceae 
and Monotropaceae are not numerous; in fact, hairs are absent 
entirely on the leaves of all the Pyrolaceae. In Pterospora 
there are present on the margin of the leaves, stalked glands 
composed of a multiserrate stalk and a glandular head formed 
of several cells. This type, according to Solereder, is present 
in Arbutus, Arctostaphylos alpina, A. tomentosa, Enkianthus, 
GauUheria myrsinites, and G. Jiispida. In Sarcodes stalked 
glands on the margin and also on the lower surface of the upper 
leaves are very similar in structure to those of Pterospora, ex- 
cept that in Sarcodes the glandular head is not as enlarged as 
in Pterospora. In Monotropa hypopitys another type of hair 
occurs. It is unicellular, short, blunt, and the waxy covering 
is somewhat warted. This simple type is common throughout 
the Ericaceae. 

Chlorophyll grains occur in the epidermis of many plants 
belonging to the Ericaceae and the Pyrolaceae. Petersen re- 
ports their presence in the upper epidermis of the leaf of Rhodo- 
dendron lapponicum, the lower epidermis of Vaccinium vitis- 
idaea f. pumila, upper and lower epidermis of Vaccinium oxy- 
coccus, and states that Lidforss (45) reports their presence in 
the upper epidermis of Ledum palustre, Loiseleuria procumbens, 
Phyllodoce coerulea, Andromeda polifolia, Lyonia calyculata, and 
in both upper and lower epidermis of Arctostaphylos uva-ursi 
and A. alpina. In the Pyrolaceae, Petersen reports their 
presence in the lower epidermal cells of the leaf of P. rotundi- 
folia var. grandiflora, and P. minor, in both upper and lower 
epidermal cells of P. secunda, P. uniflora, C. umbellata, and the 
writer has noted their presence in both upper and lower epi- 
dermal cells of P. elliptica and C. maculata. 

The palisade tissue varies in Ericaceae from five to six layers 
in Rhododendron lapponicum, Vaccinium vitis-idaea and Ledum 



Monotropaceae with Reference to Ericaceae 87 

Palustre; to three to four in Loiseleuria procumbens, Epigaea 
repens, and Lyonia calyculata; to two to three in Ledum groen- 
landicum, Kalmia latifolia, Agarista revolnta, Diplycosia pilosa, 
and Andromeda polijolia; to two in Cassiope hypnoides, Gay- 
lussacia pinifolia, Dendrium buxifolium, and Vaccinium uligi- 
7iosium: to one in Vaccinium myrtillus and Chiogenes hispidula. 

The Pyrolaceae show a gradual reduction in the number of 
palisade layers. Chimaphila umbellata has three; C maculata 
two; P. chlorantha and Moneses uniflora one; P. rotundifolia, 
P. secunda, P. minor all have no palisade tissue developed, nor 
is it present in any of the Monotropaceae. 

Conglomerate and single crystals are common in many mem- 
bers of the Ericaceae occurring in the palisade or spongy paren- 
chyma, or in both. Niedenzu (56) has given a table of their 
distribution in the Arbutoideae and Vaccinioideae (pp. 175, 176). 
In the Pyrolaceae only conglomerate crystals occur and these 
are found in the spongy mesophyll. The writer has found them 
in C. umbellata, C. maculata, P. rotundifolia, P. eliiptica, Moneses 
uniflora. Rommel (65) reports their presence in P. minor and 
P. chlorantha. The writer has not found any crystals in the 
leaves of any of the Monotropaceae examined. 

The Inflorescence 

In C. umbellata, the flowerstalk is about i dm. long with 
no scales. The flowers are arranged in a 2-8-flowered corymb, 
each flower on a slightly recurved pedicel 8-12 mm. in length. 
This comes off" in the axil of a linear subulate, smooth, deciduous 
bract. 

In C. maculata, the flowerstalk is about i dm. long with no 
scales. There are 1-5 flowers arranged in a corymb; the pedicels 
are pubescent and about 16-18 mm. long. The bracts are 
linear, about 15 mm. long, with the margin appearing slightly 
fimbriolate near the apex on microscopic examination. 

In P. rotundifolia, the entire flowerstalk is 2-3 dm. in length 
with two scales. There are 6-20 flowers arranged in a raceme, 
each flower being borne on a smooth recurved pedicel, 6-10 
mm. long, in the axil of a lanceolate bract that is 5-8 mm. long. 
This also, when examined microscopically, shows a somewhat 
fimbriolate margin toward the apex. 



88 Henderson — Comparative Study of Pyrolaceae atid 

In P. elliptica, the flowerstalk is 1-2 dm. in length with 0-2 
scales; the raceme is 6-15-flowered; the bracts are linear-lanceo- 
late, 5-6 mm. long, about equal in length to the smooth pedicels. 
The margin of the bracts is entire. 

In P. secunda, the flowerstalk is 1-2 dm. in length, with 1-4 
scales. The flowers, 6-17 in number, are arranged in a raceme 
with the flowers all turned to one side. The bracts are subulate- 
ovate, slightly shorter than the pubescent pedicels, which are 
4-5 mm. in length. 

In P. minor, the flowerstalk is 0.5-2 dm. in length with one 
or two scales; there are 5-17 flowers borne in a raceme, each 
on a pedicel equal in length to the 2-3-mm. subulate bracts. 

In P. chlorantha, the flowerstalk is 0.5-2 dm. in length, with 
a single scale. There are 2-8 flowers borne in a raceme. The 
bracts are lanceolate, 4 mm. long, shorter than the pedicels, 
which are 5-6 mm. in length. 

In P. aphylla, the flowerstalk is 1-3 dm. in length, with 
numerous scales extending from the base upward. There are 
8-25 flowers borne in a raceme, each on a recurved pedicel about 
5 mm. in length. The bracts are lanceolate, 3-5 mm. in length. 

In Moneses uniflora, the flowerstalk bears one flower and is 
0.5-1.3 dm. in length with one scale, similar in form to the one 
bract. This is ovate, about 4 mm. in length, and, under the 
microscope, is seen to have numerous unicellular hairs along 
the margin. The margin becomes slightly fimbriolate toward 
the apex. 

In all members of the Monotropaceae examined, green leaves 
are not produced, their place being taken by scales which grad- 
ually pass with little change of structure into bracts subtending 
the flowers. 

In Monotropa hypopitys, the flowerstalk — in this case the 
entire ascending axis — is 1-3 dm. tall. The flowers are numer- 
ous, 3-15, each borne on a pubescent pedicel that is 3 mm. in 
length. The bracts are narrow ovate, yellow, 10-12 mm. in 
length, shorter than the flower. The outer surface and the 
margin of these bracts are covered with unicellular hairs. 
Toward the apex, the margin becomes somewhat irregularly 
toothed. 

In M. uniflora, there is one flower produced at the end of 
the o. 5-1. 5-dm. -tall flowerstalk. The bracts, white in color, 



Monotropaceae with Reference to Ericaceae 89 

are narrower than the scales below, and are about ia-12 mm. 
in length, shorter than the flower, and are quite numerous at 
the base of the flower. They are much thinner in texture than 
in M. hypopitys. No hairs are present in these. The margin 
becomes somewhat irregularly toothed toward the apex. 

In Sarcodes sanguinea, the flowerstalk is 1-5 dm. in length. 
The flowers are numerous, borne in racemes, each on a pedicel 
that is pubescent with short glandular hairs. Those of the 
lower flowers are longer than those of the upper. The bracts, 
crimson in color, become much narrower than the lower scales 
and are longer than the flowers, 2.5-6 cm. long. The bracts 
ensheathe the buds as they come above the surface of the ground. 
Later they curve backward. The whole outer surface and the 
margins of the bracts are covered with glandular hairs. Near 
the apex, the margin appears somewhat toothed. 

In Pterospora andromedea, the flowerstalk is 3-1 1 dm. in 
length. The numerous flowers are borne in racemes. The 
purplish brown bracts are linear, about 5 mm. in length, as 
long as, or longer than, the pubescent pedicels. Numerous 
glandular hairs are present on the margin and lower surface. 

In Pleuricospora fimhriolata, the flowerstalk is 1-2.5 dm, 
long. Numerous flowers are borne in a raceme. The brownish 
bracts are smooth, 1-2 cm. long, have a fimbriolate margin. 

In Sch-iVeinitzia odorata, the flowerstalk is 5-1 1 cm. long. 
Flowers are borne in a dense terminal raceme. Bracts are 
purple or purplish brown and about 8 mm. in length. 

In Allotropa virgata, the flowerstalk is 1-5 dm. long. Numer- 
ous flowers are borne in a raceme. The whitish bracts are 
linear-lanceolate, 1-2.5 cm. in length, narrower than the lower 
scales. 

In Newherrya congesta, the flowerstalk is 1-5 dm. tall or less, 
terminated by a "corymbiform glomerule"; "scales ovate brown- 
ish — the upper ones narrower, all obtuse irregularly erose" (72). 

In Newberrya spicata, the flowerstalk is mostly less than 
I dm. tall, terminated by a dense spike; scales oblong, brownish, 
sometimes acutish erose fimbriate (72). 

In typical Ericaceae, the inflorescence is generally racemose, 
or condensed to a corymb or umbel as in Rhododendron, or 
solitary axillary as in Kalmia hirsuta, Phyllodoce, Cassiope, 
Chiogenes. In the Pyrolaceae and Monotropaceae, Pyrola, 



90 Henderson — Comparative Study of Pyrolaceae and 

Monotropa hypopitys, Sarcodes, Pterospora, Pleuricospora, 
Schweinitzia, Allotropa have racemose inflorescence; Chimaphila, 
and Newherrya corymbose; Moneses unijiora and Monotropa 
uniflora solitary terminal flowers, thus forming a series parallel 
to that of the typical Ericaceae. 

The bracts in the Ericaceae are generally small, green, often 
deciduous as in Chimaphila and Pyrola. In the Monotropaceae, 
they have become much larger, and like the fleshy scale-like 
leaves. There is a transition from forms like C. umbellata and 
C. maculata, with no scales on the flowerstalk, to P. rotundifolia, 
P. elliptica, P. minor, P. chlorantha, Moneses uniflora with 1-2 
scales; P. secunda with generally 4; P. aphylla with still more 
numerous scales and no, or rarely, green leaves, and finally 
to Monotropa, Sarcodes, Pterospora, Pleuricospora, Schweinitzia, 
Allotropa, and Newberrya, where the scales are very numerous, 
fleshy, entirely replacing green leaves at the base and becoming 
only slightly modified toward the flowers. 

In the Ericaceae the plants live for two or more years before 
flowering and the flower buds appear in the autumn of the year 
preceding their expansion. This also occurs in all members of 
the Pyrolaceae. In the Monotropaceae the underground part 
lives for a year before sending up a flowering axis and buds do 
not appear above ground until the spring, when they are ready 
to expand — this of course due to the fact that the ascending 
axis in the Monotropaceae is annual. 

The Sepals 

In Chimaphila umbellata there are five green sepals united 
at the base. The lobes are rounded, about 2 mm. in length, 
and appear entire. Under the microscope, however, the margin 
appears slightly fimbriolate. 

In C. maculata, there are five small oval sepals, united at the 
base. The segments are slightly longer than in C. umbellata, 
being 3 mm. in length, about one-fourth the length of the petals. 
Simple unicellular hairs are present along the margin. 

In P. rotundifolia there are five green sepals united at the 
base. The five lobes are lanceolate acute with spreading tips 
and are 3-3.5 mm. long, one-half to one-third the length of the 
petals. 



Monotropaceae with Reference to Ericaceae 91 

In P. elliptica, the lobes of the sepals are much shorter than 
in P. rotnndifolia; they are triangular, ovate-acute, about 2 mm. 
long, not one-fourth the length of the petals. 

In P. secunda, the calyx lobes are "oval or elliptic, i mm. 
long, rounded at the apex" (72). 

In P. minor, the calyx lobes are "triangular-acute or short- 
acuminate, as broad as long" (72). 

In P. chlorantha, the calyx lobes are "triangular, acutish 
or obtusish, about as broad as long" (72). 

In P. aphylla, the calyx lobes are "ovate-triangular, acute, 
as long as broad, or slightly longer, about 1.5 mm. in length" 

(72). 

In Moneses uniflora, the calyx lobes are ovate, obtuse, 3 mm. 
long, with numerous unicellular hairs along the margin. 

In Monotropa hypopitys, the sepals are distinct, not united. 
They consist of 2-3 narrow bract-like structures about 6-8 mm. 
long, yellow in color, with a few long unicellular hairs on the 
upper surface and numerous ones on the margin and lower 
epidermis. 

In Monotropa uniflora, there are 2-4 white bract-like sepals, 
1-1.5 cm. long, which are not united. These are glabrous, 
except for a few hairs on the upper surface. The margin begins 
to show a slight irregular toothing near the axis. 

In Sarcodes sanguinea, there are five fleshy oblong-lanceolate 
crimson sepals about 2 cm. in length. Oliver states that these 
are distinct, but the writer finds that they are very slightly 
united at the base, and have a fimbriolate margin and the entire 
outer surface covered with glandular hairs. 

In Pterospora andromedea, the sepals are brownish, united; 
the lobes are lanceolate, about 4 mm. in length, and are glandu- 
lar pubescent. 

In Pleuricospora fimhriolata, the four whitish sepals are sep- 
arate lanceolate, 8-9 mm. long, and have a fimbriate margin. 

In Schiveinitzia odorata, the sepals are five, purple or purplish 
brown, becoming lanceolate, 8-12 mm. long, usually acute. 

In Allotropa virgata, there are five broad distinct white sepals, 
"orbicular ovate to rhombic ovate, 4-6 cm. long, erose" (72). 

In Newberrya congesta, the sepals are two brownish distinct, 
linear or nearly so (72). 

In Newberrya spicata, the sepals are two, brownish-"spatulate, 
erose-fimbriate" {72). 



92 Henderson — Comparative Study of Pyrolaceae and 

In Cheilotheca there are 3-4 oblong lanceolate sepals (31). 

In the Ericaceae, the sepals are usually green or brownish 
(exceptions to this occur as in Cassiope hypnoides with a red 
calyx), generally united, at least at the base. In Kalmiella 
and Cladothamnus pyrolaefloriis, the sepals are almost distinct. 
In a few the sepals are distinct as in Epigaea repens. All of 
the Pyrolaceae are similar in this characteristic to the Eric- 
aceae — the sepals all being slightly united. In the Monotro- 
paceae, Pterospora has a slightly united reddish brown calyx 
with narrow linear to lanceolate lobes. Sarcodes has a slightly 
united calyx, but the sepals are petalloid, crimson and large, 
almost as long as the corolla. In all of the other genera, the 
sepals are separate, 5-4-3 in number and petalloid, showing a 
gradual transition from small green united sepals in Ericaceae 
to large petalloid distinct ones in the most reduced members of 
the Monotropaceae. 

In the Ericaceae, the sepals are often hairy, the hairs similar 
to those found in the Pyrolaceae and Monotropaceae. In 
Cladothamnus campanidatus, for instance, simple hairs like 
those of Monotropa hypopitys and stalked glandular hairs like 
those of Pterospora and Sarcodes occur. 

The Petals 

In C. umhellata, the petals are five, separate, concave, orbicu- 
lar, pinkish in color, and 5-6 mm. in length. Under the micro- 
scope they show a fimbriolate margin that is ciliolate with 
numerous unicellular hairs. 

In C. maculata, the petals are similar to those of C. umhellata 
except for the color, which is white. 

In P. rotiindifolia, there are five distinct, spreading, white, 
concave, roundish-obovate petals, about 7 mm. long with an 
entire margin. 

Those of P. elliptica are similar except that they are greenish 
white in color and are about 6 mm. long. 

In P. secunda, there are five oblong or elliptic erect petals, 
4-5 mm. in length, greenish white in color. 

In P. minor, there are five white or rose-colored, orbicular, 
concave, erect petals, 3-4 mm. in length. 

In P. chlorantha, there are five greenish white, oval or elliptic, 
petals, 5-6 mm. in length. 



Monotropaceae with Reference to Ericaceae 93 

In P. aphylla, there are five obovate petals, 6-8 mm. in length, 
whitish or tinged with brown or green on the outside. 

In Moneses uniflora, the petals are five, occasionally six, 
concave, orbicular, white or pinkish, about i cm. in length, 
with a fimbriolate margin that is only visible under the micro- 
scope. 

In Monotropa hypopitys, there are 5-4 yellow petals (five in 
the terminal flower, four in the lateral flowers). These are 
about I cm. in length and are narrow with a saccate base. Al- 
though the petals are not united, they are erect, with margins 
meeting, so that the flower appears campanulate. They are 
covered on the upper and lower surfaces with numerous simple, 
unicellular hairs. 

In M. uniflora, there are five, occasionally six, white or pink- 
ish petals that appear somewhat similar to those of M. hypopitys, 
except that they are larger (1.5 cm. in length) and thinner in 
texture, and only sparsely hairy on the inner surface, and en- 
tirely glabrous on the outer surface. 

In Sarcodes sangninea, the petals are five in number, united, 
campanulate (1-1.5 cm. in length), the five lobes are broad, 
rounded, and slightly spreading. No hairs are present on either 
surface. 

In Pterospora andromedea, the corolla is urceolate, the five 
petals are white in color and united. They are 7-8 mm. in 
length, the lobes ovate to reniform, very short and recurved. 

In Pleuricospora fimhriolata, there are five separate, slightly 
spreading, white petals, each narrowly oval, with a fimbriolate 
margin. 

In Sckweinitzia odorata, the corolla is pink in color. It is 
campanulate, with five lobes, which are ovate, shorter than the 
tube. The tube is 5-saccate at the base, as in Monotropa. 

In Allotropa virgata, petals are absent. 

In Newberrya congesta, the corolla is urceolate. The four 
lobes are ovate, about one-third as long as the tube which is 
pubescent within. 

In N. spicata, the corolla is oblong campanulate, the four 
lobes oblong-ovate, about one-half as long as the tube which is 
pubescent within. 

In Cheilotheca there are three erect, linear-oblong, yellow-red 
petals, 2.5 cm. in length. 



94 Henderson — Comparative Study of Pyrolaceae and 

In the Pyrolaceae, all of the species have five distinct petals. 
This is also true of the most primitive group of the Ericaceae, 
namely, the Rhododendroideae-Ledeae where Elliottia has four, 
Tripetaleia three, Cladothamnus five, Bejaria seven, and Ledum 
five petals. Distinct petals also occur in several members of 
the Monotropaceae, i.e., Monotropa hypopitys with 5—4, M. 
nniflora 5-6, Pleuricospora 5-4, and Cheilotheca three. In other 
members of the Monotropaceae the petals are united. In 
Pterospora, the corolla is urceolate, resembling that of Andro- 
meda. In Sarcodes and Schzveinitzia it is campanulate, and in 
Newberrya urceolate to campanulate. Urceolate and campanu- 
late corollas are quite characteristic of many of the Ericaceae. 
In the Ericaceae proper one can trace all transitions from a 
fiat saucer-shaped corolla with separate petals, as in Clado- 
thamnus; to shallow campanulate, as in Loiseleuria procumhens; 
to deep campanulate, Epigaea; to campanulate becoming slightly 
irregular bilobed, as in Rhododendron; to urceolate in Andromeda 
and Vaccinium; to deeply urceolate in Erica and Thibaudia. 
In the Monotropaceae, all these stages do not occur; there is 
quite a big gap between a corolla with distinct petals, as in 
Monotropa, and an urceolate one as in Pterospora, or campanu- 
late as in Sarcodes and Schweinitzia. This would point to the 
view that perhaps these three arose from a higher group of the 
Ericaceae, and that the others arose from the Rhododendroideae- 
Ledeae with distinct petals. The very great similarity of these 
to each other (particularly Sarcodes and Pterospora, the writer 
having no good material of Schweinitzia) in all of their parts, 
and the rather great difference in structure between them and 
all other members of the Monotropaceae and Pyrolaceae give 
further evidence toward this view. In Chimaphila and P. 
rotundifolia and P. elliptica the corolla is slightly irregular — 
one petal extends downward so as to form a resting place for 
the insect. This parallels the condition in Rhododendron where 
the corolla is slightly bilabiate. 

The presence of hairs on the inner surface of the petals seen in 
Monotropa is a characteristic of many members of the Ericaceae. 

The Stamens 

In all of the Pyrolaceae, the stamens, ten in number, are 
arranged in the bud so that the pores of the anthers point down- 
ward. When the fiower opens, the anthers tilt backward, so 



Monotropaceae with Reference to Ericaceae 95 

that the pores point upward. This is to insure pollination. 
Pollen grains occur in tetrads in all of the Pyrolaceae except 
P. secunda. 

In C. umbellata, the filaments have two lobes toward the base. 
These bear numerous unicellular hairs along the margin. The 
anthers are violet in color and attached nearer the pore bearing 
end, and have two short horns opening by apical pores. 

The stamens of C. maculata are similar to those of C. umhellata 
except that there are present on the margins of the lobes of the 
filament uniserrate hairs composed of 2-3 simple cells placed 
end on end. The anthers are attached near the middle. 

In P. rotundifolia and P. elliptica, the filaments are not lobed 
and the horns on the anthers are very slightly developed. 

In P. secunda, the anthers are oblong, opening by large pores. 
No horns are present. The pollen grains are single. 

In P. minor, the anthers are not horned. 

In P. chlorantha, the horns on the anthers are well developed, 
being about 0.5 mm. in length. 

In P. aphylla, the horns are well developed, being about i mm. 
in length. 

In Moneses nniflora, the filaments are awl-shaped, the anthers 
are prominently two-horned, the horns 0.5 mm. in length. 

In Allotropa virgata, the stamens are described as having 
slender filaments, "anthers short, lobed, unappendaged, extrorse 
in the bud, introrse in anthesis, the sacs opening to near the 
middle by a chink." (72). This is the only member of the Mono- 
tropaceae that possesses the faculty of changing the position 
of the anthers in the opening bud, thus forming a connection 
between the Pyrolaceae and the Monotropaceae. Pollen grains 
are simple as in all the other members of the Monotropaceae. 

In Monotropa hypopitys, the filaments are long, with unicellu- 
lar hairs. They are pressed closely up against the ovary ex- 
tending up to the stigmatic disk, the five opposite the petals 
being shorter than those opposite the sepals. The anthers 
are short, kidney-shaped, with transverse dehiscence, opening 
into two unequal valves. 

The stamens of M. nniflora are similar to those of M. hypopitys. 

In Sarcodes sanguinea, the filaments are long, slightly ex- 
panded at the base, extending up slightly further than half the 
length of the corolla, lying in the grooves of the ovary, and 



96 Henderson — Comparative Study of Pyrolaceae and 

bearing on their apices the rather long expanded anthers which 
open by two oval pores at the summit, turned toward the outside. 

In Pterospora, the filaments are slender, the anthers short, 
each sac with an awn. The dehiscence is longitudinal. 

In Pleuricospora, there are 10-8 stamens; the filaments are 
long and glabrous, the anthers long and narrow, opening by a 
longitudinal slit. 

In Schweinitzia odorata, the anthers are short, opening by 
terminal pores. 

In Newberrya, the stamens are 10-8 in number; the filaments 
are slender with long hairs. The anthers are oblong, erect on 
the tip of the filament, opening lengthwise. 

In Cheilotheca, the anthers are erect on the filaments, and 
have longitudinal dehiscence (31). 

In the Ericaceae, types of stamen similar to all those of the 
Pyrolaceae and Monotropaceae are present. Many of them 
have hairy filaments, as in Ckimaphila and Monotropa. Simple 
oblong anthers occur as in P. minor, P. secunda, and Sarcodes 
with apical pores and not horned, e. g., Kalmia glauca (12, p. 25, 
Fig. 17); others with exceedingly long tubes, as in Vacciniuni 
vitis-idaea (12 Fig. 17) longer than in any of the Pyrolaceae 
and Monotropaceae. In the Pyrolaceae and Monotropaceae 
dehiscence of the anthers occurs in the same way as in the 
Ericaceae. Apical porous is quite common. Longitudinal de- 
hiscence also occurs in practically all groups of the Ericaceae. 
In the Rhododendroideae-Ledeae, EUiottia and Clndothamnus 
have longitudinal, Bejaria and Ledum apical porous dehiscence. 
Transverse dehiscence occurs in the group Arbutoideae-Andro- 
medae. 

In the Ericaceae, the anthers may or may not be awned. 
In Figs. 17 and 18, p. 26, Drude (12) has figured Erica tetralix, 
Arbutus unedo, Calluna vulgaris with awned anthers, Vaccinium 
vitis-idaea, Kalmia glauca. Rhododendron flavum, and Leiophylliim 
buxifolium without awns. As a general rule the more primitive 
members of the Ericaceae with open flat expanded flowers do 
not have awned anthers, those with urceolate corollas gener- 
ally do. This rule also applies to the Pyrolaceae and Mono- 
tropaceae ; Pterospora the only member with awned anthers, has 
an urceolate corolla. The awns when touched by an insect 
tilt the anthers so that the pollen is dropped out on the insect's 
back. 



Monotropaceae with Reference to Ericaceae 97 

The pollen grains of Ericaceae always occur in tetrads. This 
is true also of the Pyrolaceae except for P. secunda. This 
species forms a transition to the Monotropaceae where all the 
pollen grains are single. 

The Pistil 

In C. umbellata, the ovary is somewhat flattened-globose, 
with its outer surface ridged from the anthers being pressed up 
against it. The outer surface is covered with simple papillar 
hairs. It is completely five-celled, with a central placenta at 
the base, but the upper half is one-celled through the failure 
of the bilobed parietal placentae to meet and fuse in the center. 
The space between the placentae is, however, very small, so 
that it appears more like a five-celled ovary than a one-celled 
one. The placentae bear numerous anatropous ovules. The 
style is short, top-shaped. The stigma is broad and five-crenate, 
with a disc-shaped border. At the base of the ovary is a circular 
disc which secretes nectar. 

In C. mactilata, the ovary is similar to that of C. umbellata, 
the outer surface being ridged from the anthers, but no hairs 
are present. The number of cells, etc., is the same as in C. 
umbellata. The nectariferous disc is present, similar to that 
of C. umbellata. The style, however, is slightly longer; the 
five stigmatic lobes protrude slightly more from the disc. 

In P. rotundifoHa, the ovary is five-lobed, with glabrous 
outer walls. The same transition from a five- to a one-celled 
state occurs, as in Chimaphila, this being characteristic of the 
family. No nectariferous disc is present. The style is long 
declined, with the apex turned upward. The stigma consists 
of five narrow, erect lobes, which extend out from the top of the 
style that forms a rim beneath the stigmatic lobes. 

In P. elliptica, the ovary and style are similar to those of 
P. rotundifoHa. No nectariferous disc is present. The lobes 
of the stigma are however slightly longer, and the rim at the 
tip of the style greater in diameter than in P. rotundifoHa. 

In P. secunda the ovary is five-lobed, subglobose, with ten 
small nectariferous lobes at the base. The ovary is five-celled 
for most of the distance; the region where the placentae fail to 
meet is limited because of the deep insertion of the style. This 
is erect, straight, exserted, about 4 mm. in length. The stigma 
is peltate, much broader than the style, with five diverging lobes. 



98 Henderson — Comparative Study of Pyrolaceae and 



In P. minor there are no nectaries at the base of the five- 
lobed, incompletely 5-celled, ovary. The style is short, erect, 
I mm. in length, included in the petals. 

In P. chlorantha the ovary is five-lobed, with 10 small nec- 
tariferous lobes at the base. The style is long, about 7 mm., 
exserted a little beyond the corolla, thickened upwards and 
declined as in P. rotundifolia and P. elUptica. 

In P. aphylla the ovary is five-lobed with ten small nectari- 
ferous lobes at the base. The style is erect, short, 3 mm. in 
length. 

In Moneses uniflora the ovary is ten-lobed. It is five-celled 
for the most part because the deep insertion of the style limits 
the region where the placentae fail to meet. No nectariferous 
lobes are present. The style is erect, inserted rather deeply 
into the ovary. It widens out toward the extremity forming 
a rim that is wider than that of P. elUptica, and with a stigma 
consisting of five fieshy lobes that are longer than in P. elliptica. 





Fig. 8. Transverse section ovary Pleuricospora fimbriolata X 25. 

1. Near base. 

2. At middle. 

In Monotropa hypopitys the ovary is ovoid, io-8-lobed. As 
in the Pyrolaceae it is 5-4-celled at the base and one-celled 
above with 5-4 bilobed parietal placentae. At the base of the 
ovary there are 10-8 downward directed spur-like processes, 
which extend between the stamens and secrete nectar into the 
saccate bases of the petals. The style is thick and fleshy, 
longer than the ovary, it and the ovarian wall being strongly 
pubescent with unicellular hairs. Toward the top, the style 



Monotropaceae with Reference to Ericaceae 



99 



expands slightly, forming a ring, below this is a circle of hairs. 
The upper surface is hollowed out into a funnel-shaped 4-5- 
sided stigma. 

In M. uniflora the ovary is ovoid, larger and more distinctly 
ten-lobed than in M. hypopitys. At the base are developed the 
ten nectaries similar to those of M. hypopitys, but larger. The 
style is shorter, the stigma much less hollowed out than in 
M. hypopitys, appearing more like a flat disc. 

In Sarcodes sanguinea the ovary is smooth, ten-lobed, each 
lobe extending between two stamens and continued down into 
a nectar-secreting portion. It is five-celled at the base, becom- 
ing one-celled above as in Monotropa. The style is erect, bear- 
ing a five-lobed stigma. 

In Pterospora the ovary is ten-lobed, depressed. It is five- 
celled below and one-celled above as in all the preceding. No 
nectaries are present. The style is short and broad, the stigma 
peltate-capitate, slightly live-lobed. 




Fig. 9. Longitudinal section flower Newberrya spicata at base X 25. 
F = filament, N = nectary, P = petal, S = sepal. 

In Pleuricospora the ovary is ovoid, not lobed, the epidermal 
cells bearing distinct pointed papillae. It is four-celled at the 
base (Fig. 8, i) and for about one-sixth the length of the ovary, 
but further up (Fig. 8, 2) the four placentae fail to meet and 
do not extend far into the interior of the ovary, so that it appears 
as a one-celled ovary with parietal placentae. There are no 
nectaries present. The style is short and broad, the stigma 
depressed capitate. 

In Schweinitzia the ovary is five-lobed with no downward 
directed nectaries at the base; it is five-lobed for about half the 
distance; the placentae do not extend in quite as far as in Pyrola. 



100 Henderson — Comparative Study of Pyrolaceae and 

The epidermal cells of the ovarian wall are slightly papillate. 
The style is short and thick, the stigma disc-like pentagonal. 

In Allotropa the ovary is five-lobed. It too is five-celled 
at the base, one-celled above. There are ten small slightly 
down-directed nectaries at the base of the ovary. 

In Newherrya the ovary is five-lobed, five-celled at the base, 
one-celled above. There are ten downward directed spur-like 
nectaries at the base of the ovary (Fig. 9). The ovary and style 
are pubescent with simple unicellular hairs. The stigma is 
depressed capitate. 

In Cheilotheca the ovary is "fusiform, one-celled, narrowed 
into the short cylindric style; stigma globose conical; placentae 
six, parietal, bifid, the long branches on all sides covered by 
numerous ovules" (31). 

In the Ericaceae a five-lobed, completely five-celled ovary is 
characteristic. In the Pyrolaceae and Monotropaceae there is 
every transition from a five-celled ovary with central placenta, 
as in the Ericaceae, to an incompletely five-celled ovary with 
the placentae deep parietal and almost meeting, as in all the 
Pyrolaceae, also Sarcodes and Monotropa; to an incompletely 
five-celled ovary with the placentae not so deep parietal, so 
that there is a good space between them, as in Schweinitzia; 
to Pleuricospora where the ovary is four-celled for only a short 
distance, then one-celled above with parietal placentae that 
are close to the ovary wall. Drude (12) states that all the 
Pleuricosporeae are one-celled. The writer finds the condition 
in Newherrya as in the Pyrolaceae; in Pleuricospora 4-1 -celled 
as above; no material of Cheilotheca could be obtained for exam- 
ination. Hooker (31) describes it as being one-celled with six 
parietal bifid placentae. 

In Ericaceae the ovary is often covered with hairs, peltate 
glandular in Rhododendron lapponicum; glandular and setaceous 
in Ledum palustre; glandular in Phyllodoce coerulea. In the 
Pyrolaceae and Monotropaceae simple hairs are present in 
Chimaphila umhellata, in Monotropa hypopitys; and small papillae 
are present in Schweinitzia odorata and Pleuricospora fimbriolata. 

The ovules in all three families are always anatropous. Corre- 
lated with the great numbers of ovules produced in the Pyrola- 
ceae and Monotropaceae, is the rather remarkable number of 
pollen tubes developed from germinating pollen grains on the 



Monotropaceae zvith Reference to Ericaceae 



lOI 



stigma. These tubes pass down through the stylar canals and 
spread over the placental surfaces. They are most numerous 
in M. uniflora. 

In practically all members of the Ericaceae there is at the 
base of the ovary a circular or crenately lobed nectary. In 
Chimaphila this is represented by a narrow collar-like rim. 
It is absent entirely in P. rotundifolia, P. clliptica, P. minor, 
Moneses uniflora, Pterospora, Pleuricospora. The disc or nectary 
is not continuous in any others of the Pyrolaceae or Mono- 
tropaceae, being represented by ten very small swellings in 
P. secunda, P. chlorantha, P. aphylla, and Sarcodes sanguinea; 
and by ten slightly larger and down directed lobes in Allotropa, 
Schweinitzia, Neivberrya, and Monotropa. 




Fig. 10. Longitudinal section seed of Pyrola rotundifolia X 300. 
E = embryo. 



The Fruit and Seed 

In the genus Chimaphila, the capsule is depressed-globose, 
five-valved, splitting from the apex downward. The valves 
are smooth along the edges. After the flower is pollinated, 
the pedicel straightens up so that the fruit is erect. This is 
true for the entire family. The seeds are small, numerous, and 



102 Henderson — Comparative Study of Pyrolaceae and 

consist of a thin cellular coat with an endosperm composed of 
a few large cells. The embryo has no form, but consists of 
several cells. 

In the genus Pyrola, the capsule is five-lobed, splitting from 
the base upward. The valves are cobwebby on the edges, a 
distinction from the genus Chimaphila. The seeds in P. rotundi- 
fblia (Fig. lo) and P. elliptica are similar to those of Chimaphila. 

In Moneses uniflora, the capsule is five-lobed, splitting from 
the base upward. The valves are smooth on the edges. 

In Monotropa hypopitys, the capsules are oval, 5-4-celled, 
loculicidal. The seeds have a thin loose cellular covering; 
the endosperm consists of a very few large cells — much fewer 
and larger than in Pyrola; and the embryo itself is reduced to 
nine cells according to Koch (43), and five according to Solms- 
Laubach (74). 

In Monotropa uniflora, the capsule is ovoid, dehiscence as in 
M. hypopitys. The seeds are similar to those of M. hypopitys 
in the number of endosperm cells, but appear to be even more 
reduced in the number of cells in the embryo, the writer's mate- 
rial showing only two. 

In Sarcodes, the capsule is spheroidal, 9-21 mm. broad, with 
circumscissile dehiscence, the line of dehiscence 1-1.5 mm. 
below the base of the style. Oliver has described and figured 
the seeds of this. In regard to the amount of endosperm and 
number of cells in the embryo he states that it is very similar 
to that of M. hypopitys. 

In Pterospora, the capsule is five-lobed, five-celled, loculicidal, 
the valves cohering with the columella. The seeds are very 
numerous, ovoid, and are broadly winged at the apex (Drude 
(12), p. 10, Fig. 6-K). 

In Pleuricospora, the capsule is ovoid, one-celled. 

In Schweinitzia, the capsule is ovoid, five-celled, seeds nu- 
merous. 

In Allotropa, the capsule is "spheroidal, 4-5 mm. broad" (72). 
In seeds examined by the writer, the endosperm shows the same 
number of cells as in Monotropa. 

In Newherrya, the capsule is short, usually ovoid. The writer 
had no ripe capsules, but found the ovary five-celled, so concludes 
that the capsule is five-celled also. 



Monotropaceae with Reference to Ericaceae 103 

In Ericaceae, the fruit is a capsule, with septicidal or loculicidal 
dehiscence, or a berry. In the Pyrolaceae and Monotropaceae 
the fruit is a capsule, as in the primitive Ericaceae. It is char- 
acteristic of many Ericaceae, e.g., Cassiope hypnoides, C.tetragona, 
Phyllodoce coerulea, that after flowering (in species with droop- 
ing flowers) the pedicels straighten out so that the fruit becomes 
erect. This is characteristic of all of the Pyrolaceae and Mono- 
tropaceae. 

In typical Ericaceae, the seeds are small, the largest 1-2 mm. 
The endosperm is well developed, the embryo distinctly formed, 
a root and two cotyledons always present. In the Pyrolaceae 
and Monotropaceae the seeds are smaller and more numerous. 
In structure they are much reduced. The endosperm in the 
Pyrolaceae consists of relatively few large cells — the embryo 
of about 25-30 cells with no trace of cotyledons. In the Mono- 
tropaceae the number of endosperm cells is still less and the 
cells are larger, the embryo also is very small, composed of only 
nine or five cells (43, 74). 

Summary 

In the Ericaceae the plants are shrubby or sub-shrubby. 
The Pyrolaceae show a gradual reduction from sub-shrubby in 
Chimaphila to herbaceous in Moneses. The Monotropaceae are 
entirely herbaceous. The underground rhizome, producing ad- 
ventitious buds and roots, in many of the Ericaceae, in Chima- 
phila and Pyrola, gradually has its function of producing buds 
and roots taken over by the root which becomes long and hori- 
zontal in Moneses, becoming condensed to short and fleshy in 
the Monotropaceae. There is a gradual increase in the amount 
of hyphal investment in the roots from Chimaphila through 
Pyrola to Monotropa, the most saprophytic, correlated with a 
gradual decrease in the number of layers in the root cap. In 
the structure of the ascending axis, there is a gradual decrease 
in the amount of wood formed, from typical Ericaceae, with 
very woody stems through Chimaphila which is as woody as 
some of the smaller Ericaceae, through Pyrola and Moneses 
which are less woody, to the Monotropaceae, reaching its climax 
in Monotropa where the amount of wood is very limited. Cor- 
related with this is a gradual increase in the amount of phloem. 
There is a gradual reduction in the size and structure of the 



104 Henderson — Comparative Study of Pyrolaceae and 

leaves from evergreen leathery in Ericaceae, Chimaphila, and 
some of the Pj^rolas, to less leathery in P. chlorantha and P. 
minor, to evergreen leaves but with deciduous structure in 
Moneses, to scales which are brownish (Pterospora), brownish 
yellow or yellow (M. hypopitys) , red {Sarcodes), brownish white 
(Pleuricospora) , to white {M . uniflora) . This is correlated with 
the gradual increase in size and persistence of the scales from 
green or brownish in the Ericaceae to herbaceous, persistent, 
but still small in the Pyrolaceae, to large fleshy and colored in 
the Monotropaceae. Stomata are very numerous on the leaves 
in the Ericaceae, become less numerous in the Pyrolaceae, very 
few in the scales of Monotropa and Pterospora and absent entirely 
in those of Sarcodes. All of these changes are correlated with 
increasing saprophytism. 

The inflorescence is a raceme or condensed to a corymb, or 
solitary in each of the three families. The sepals are green, 
united, in the Ericaceae and Pyrolaceae; brownish, united, in 
Pterospora; red, very slightly united, in Sarcodes; becoming 
separate, yellow, in M. hypopitys; and white in M. uniflora. 
The petals are 5-4, separate, to united shallow campanulate, 
to campanulate, to irregular campanulate, to urceolate in the 
Ericaceae; there are five separate expanded, to separate cam- 
panulate in the Pyrolaceae; to separate campanulate in Mono- 
tropa; to united campanulate in Sarcodes; to urceolate in Ptero- 
spora. Stamens are generally twice the number of petals in 
the Ericaceae, and always so in the Pyrolaceae and the Mono- 
tropaceae. They bear two horns in many of the Ericaceae and 
Pyrolaceae. They are awned in the urceolate corolla types in 
the Ericaceae and in Pterospora (which has an urceolate corolla) 
of the Monotropaceae. The dehiscence is apical porous, longi- 
tudinal, or transverse in the Ericaceae, apical porous in the 
Pyrolaceae; and apical porous, longitudinal, or transverse in 
the Monotropaceae. Pollen grains occur in tetrads in all of 
the Ericaceae and all of the Pyrolaceae except P. secunda. In 
P. secunda and all of the Monotropaceae they are simple. 

In the Ericaceae, the ovary is completely 5-4-celled. In 
the Pyrolaceae, in the upper half of the ovary the placentae fail 
to meet and fuse. They almost meet, so that the ovary is 
practically five-celled. In the Monotropaceae, there is a gradual 
decrease in the length of the placental in-growths to Pleuri- 



Monotropaceae with Reference to Ericaceae 105 

cospora where the placentae are placed close against the walls 
and the ovary is practically one-celled. At the base, however, 
even in this most simplified form, the ovary is four-celled. At 
the base of the ovary in practically all of the Ericaceae, there 
is a nectariferous disc. This is represented either as a collar- 
like rim in Chimaphila, or ten very small swellings as in P. 
secunda, P. chlorantha, P. aphylla, and Sarcodes or ten downward 
directed nectaries in Allotropa, Schweinitzia, Newberrya, and 
Monotropa. The ovules in all three families are anatropous. 
In the Ericaceae, the seeds are small with abundant endosperm 
and a well-formed embryo; reduced in size but increased in 
number in the Pyrolaceae with a less developed endosperm 
with larger and fewer cells, and a formless embryo composed of 
about 25-30 cells; still further reduced and more numerous in 
the Monotropaceae with an endosperm consisting of a few large 
cells and a very small embryo composed of 9-5 cells. The 
change in the ovary from five-celled with central placentae to 
one-celled (nearly so in Pleuricospora) with parietal placentae; 
and the increase in number of seeds and reduction in number 
of cells of the endosperm and embryo are all evidence of increas- 
ing saprophytism. 

Conclusions 

From the preceding summary, it is seen that all of the sup- 
posed differences between the Ericaceae and the Pyrolaceae 
are broken down, except that the ovary is completely five-celled 
in the Ericaceae, and incompletely five-celled in the Pyrolaceae. 
The distinction is so slight that it seems unreasonable to use 
it as a basis for separating the two families. The only dis- 
tinction that holds between the Pyrolaceae and the Mono- 
tropaceae is the absence of green coloring matter in the latter. 
In M. hypopitys, small grains are present in the epidermis of 
the scales. These are probably chromoplasts which develop 
from chloroplasts by degeneration. 

The Pyrolaceae and Monotropaceae therefore differ from 
the Ericaceae only in their gradually increasing saprophytism 
and in those characters which go hand in hand with this, i.e., 
the loss of green coloring matter, the reduction from shrubs 
to herbs, reduction of leaves to scales, the ovary from five- 
celled with central placentae to almost completely one-celled 



io6 Henderson — Comparative Study of Pyrolaceae and 

with parietal placentae, the increase in the number of seeds 
and the reduction in their size and in the number of cells of 
the endosperm and embryo. The writer has traced such a 
gradual transition in structure from the simplest group of the 
Ericaceae, i.e., the Rhododendroideae-Ledeae, through the 
slightly saprophytic Pyrolaceae to the completely saprophytic 
Monotropaceae. The genera Pterospora and Sarcodes seem in 
their characters to be different from the others, as if these two 
had arisen in a different line, perhaps from some of the higher 
members of the Ericaceae with campanulate or urceolate corollas. 
On account of the lack of distinct differences and the numer- 
ous resemblances and intergrading characters between the more 
primitive Ericaceae, the Pyrolaceae, and the Monotropaceae, 
the writer concludes that the last two should be considered as 
sub-families under the Ericaceae. 

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Monotropaceae with Reference to Ericaceae 107 

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toideae und Vaccinioideae. Bot. Jahrb., 9, 1888. 



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Vol. V 1920 No. 2 



CONTRIBUTIONS 



TROM THE 



Botanical Laboratory 



OF THE 



University of Pennsylvania 



University of Pennsylvania 

Philadelphia 

1920 




CONTENTS OF VOLUME V, NO. 2. 



Page 
A Morphological and Cytological Study of Reproduction in 
the Genus Acer. By William Randolph Taylor, B.S., 
M.S. (With plates vi, vii, viii, ix, x, xi,) 112 

The Morphological Continuity of Scrophulariaceae and Oro- 
banchaceae. By Irwin Boeshore, B.S. (With plates xii, 
xiii, xiv, XV, xvi) 139 



Vol. V 1920 No. 2 



CONTRIBUTIONS 



FROM THE 



Botanical Laboratory 



OF THE 



University of Pennsylvania 



University of Pennsylvania 

Philadelphia 

1920 



A MORPHOLOGICAL AND CYTOLOGICAL STUDY 
OF REPRODUCTION IN THE GENUS ACER 

By William Randolph Taylor, B.S., M.S. 
With Plates VI-XI. 

CONTENTS 

Introduction 112 

Historical Review 112 

Material and Methods 113 

Floral Development 115 

Pollen Development in Acer negundo 117 

Reduction and Somatic Divisions in Other Species 122 

Ovule Development 126 

Fertilization and Embryogeny 129 

Seedling Anatomy 131 

Summary 133 

Bibliography 134 

Explanation of Plates 134 



112 Taylor — A Morphological and Cytological 



Introduction 

At the inception of this work the writer planned to review the 
genus Acer from the standpoint of the evolutionary tendencies 
shown by the comparative morphology of the floral parts, as well 
as the relative degrees of dioecism and flowering periods of the 
difi"erent species. A preliminary survey of the available sources 
of material and information showed that it would be imprac- 
ticable to secure sufficient data to insure a comprehensive view 
of all of the sub-genera. This was especially true with respect 
to living material. On the other hand, the literature regarding 
the development of the reproductive elements was found to be 
very meagre, and in some particulars, contradictory. Since as 
many species as could be handled in a cytological study were 
within reach, an attempt to clear up the points in dispute and 
to extend our knowledge of the genus to unstudied species led 
to the abandonment of the original problem. 

Historical 

The first paper to appear dealing with the cytology of Acer 
was by Ira D. Cardiff in 1906 (2). This was primarily a study 
of synapsis and the organization of the heterotypic chromosomes, 
presenting the viewpoint of parallel pre-synaptic threads and 
paired chromomeres. He worked with Acer platanoides and sev- 
eral other plants of widely differing groups, describing an essen- 
tial similarity of behavior throughout. The reduced chromo- 
some number for the maple considered is given as eleven. 

This work was followed by a study of Acsr negundo by Chester 
A. Darling in 1909 (4), an effort to determine the basis for the 
dioecious condition in this form. The whole history of the 
maturation divisions as described by this author is at variance 
with the usual process of pollen development. The chromatin 
is said to leave the nucleolus during the presynaptic phases in 
the form of round bodies which build up the spireme on the 
linin threads. Later the spireme breaks up to form eight 
bivalent chromosome segments, while from the nucleolus bud 
off directly five more bivalents. Upon the breakdown of the 
nuclear membrane what is left of the nucleolus is said to divide 
up into a few granules which pass out from the spindle region. 



Study of Reproduction in the Genus Acer 113 

The thirteen chromosomes thus formed divide equally and there 
is found no basis in an unequal division for a differentiation 
into male or female determining'individuals. But Darling con- 
siders that in the reorganization of the nuclei in the tetrad two of 
the nuclei contain each a chromatin body lacking in the other 
two, and that this feature may be related to sex determination. 
The body in question seems to disappear soon after, during the 
passage into the resting state. 

The unusual conditions represented by this author as present 
in Acer negundo were denied in a subsequent work by D. M. 
Mottier on the same species, published in 1914 (13). Here a 
very clear and convincing account is given of the conditions 
present and a comparison made with the somewhat related 
Staphylea trifolia L. He also, besides giving a more normal 
history as that typical of the maple, disputes the correctness of 
the count, giving twelve as the probable number in one place, 
and in another suggesting either twelve or fourteen. Mottier 
incidentally gives the chromosome count in Acer ruhrnni as 
thirty-six in the reduced condition. In an earlier paper (12) 
he describes the mature pollen of this species. 

With regard to the ovule development, the only paper avail- 
able is that of Mottier on Acer riihrum, 1893 (12). He reports 
that late in March the megaspore mother-cell is evident as a 
sub-epidermal cell, which becomes more deeply placed by later 
divisions of the nucellar epidermis. Its first appearance was not 
determined. The first division in the mother-cell is followed by 
wall formation, and then the more micropylar of these again 
divides with a resulting wall. Both these cells degenerate. 
The more chalazal of the original pair divides later than the other, 
but no wall is laid down, and the embryosac by two additional 
successive divisions reaches the eight-nucleate stage. The three 
antipodals early disappear after maturity, and the polar nuclei 
fuse preliminary to fertilization. 

Material and Methods 

The writer was fortunate in being able to obtain material of 
a considerable number of species, both native and exotic in ori- 
gin. The greater part of the exotic material could not be worked 
up with thoroughness, and so will not be considered in this paper. 
Buds of Acer platanoides L. and Acer rubrum L. were made avail- 



114 Taylor — A Morphological and Cytological 

able early in the spring of 191 8 by forcing in the greenhouses. 
These were again collected at the normal flowering season, with, 
in addition, Acer pseudo-platanus L. Little was done with the 
less common introduced species until the next season, when a 
considerable series was obtained, as well as Acer negundo L. 
buds, and the root tips of some species for vegetative mitoses. 
In all, about two hundred fixations were made. The material 
was found to be extremely hard to fix properly, a tendency being 
evident for the chromosomes to clump at metaphase, which 
caused many fixations to be discarded. The solution finally 
adopted was a Strong Flemming containing less than one per 
cent, of Urea and Maltose. The bud scales were first dissected 
away and the flower mass plunged beneath the surface of alcohol 
for a moment to drive the air from the interstices, from which 
it was removed to the fixing solution. The large inflorescences 
were separated into several parts to facilitate penetration. 
Some species have resinous bud scales or tufts of hairs between 
the flowers which render it almost impossible to get satisfactory 
results. Later stages in the development of the ovules neces- 
sitated the cutting away of the ovarian walls. Except in the 
case of Acer pseudo-platanus, the root-tips used were obtained 
from greenhouse cultures. They were fixed in Weak Flemming. 
For pollen and vegetative cell studies sections were cut 4-5 
microns thick, and for embryosac and embryo studies approp- 
riate to the stages represented. The stain used throughout 
the cytological part of the work was Heidenhain's Haematoxylin. 
The writer is much indebted to the many friends who have 
by contributions of living material or otherwise, assisted in this 
work. To Dr. John M. Macfarlane acknowledgement is made 
of the original suggestion and for the complete facilities 
under which the work was conducted. For a large part of 
the fresh material of Acer rubrum L., as well as other items, he 
must thank Dr. Alice M. Russell. Through the kindness of 
Mr. Roberts LeBoutillier the writer was able to collect much 
material from Japanese species growing on his estate. Prof. 
C. S. Sargent very generously sent a considerable number of 
species from the Arnold Arboretum, but as the flowers in this 
material were largely open, they will not enter into the present 
paper to any great extent. 



SUidy of Reproduction in the Genus Acer 115 

Floral Development 

The maples fall into two classes with respect to their time 
of flowering, the one blooming before the development of the 
leaves, the other after they have begun to expand. This fact 
has been recognized in the subdivision of the genus (14). In 
the region of Philadelphia Acer saccharinum and Acer rubrum 
bloom within about ten days of each other, in late February or 
early March. Then there is a period of ten days or more before 
any other forms appear. These first two both flower before the 
leaves appear, and so also does Acer negundo, which ushers in 
the most active blooming period. A few of the exotic species 
only, seem with us to delay beyond the latter part of April. 

The early blooming of the three forms named, correlated as 
it is with a reduced perianth and marked dioecism, would lead 
one to suspect a possible difference from other species in the 
period of pollen maturation and other reproductive phenomena. 
Only one of these, however, shows such a condition. Acer sac- 
charinum, which flowers earliest in the spring, matures its pollen 
in the autumn. The writer followed the development of the 
flower buds closely during September and October, 1919, and 
found that development was very gradual till the time for the 
reduction divisions came near. Then a rapid growth in size 
accompanied the divisions. This phase came about October 
20-24. The period of the formation of the tube and generative 
nuclei appears to be in late winter, generally during early Feb- 
ruary (Fig. 27). Flowering occurs from the latter part of Janu- 
ary, by the earliest records available, to the middle of March 
in exceptionally late seasons and sporadic cases. The great 
majority of the trees flower together during the first thoroughly 
warm spell of the year. 

This species is followed by Acer rubrum, generally during the 
early part of March, though, exceptionally, earlier. Here pollen 
maturation does not take place in the fall, but during the open- 
ing of the flower buds. The reduction divisions take place 
during the swelling of the bud, and the tetrad stage is reached 
as the anthers appear between the scales at the tip. The for- 
mation of the tube and generative nuclei occurs just before the 
rapid elongation of the filaments which accompanies anthesis. 
The sperm nuclei were not seen: they are formed probably 
subsequent to the shedding of the pollen. 



Ii6 Taylor — A Morphological and Cytological 

Acer negimdo follows a week or ten days later than Acer ruhrum, 
and maturation of the pollen also occurs during the opening of 
the buds. In these three forms, with relatively condensed in- 
fioresences it might be expected that in any given bud the stages 
would be almost simultaneous, but a great variation, even in 
the lobes of a single anther, was the regular condition. The 
same holds true for Acer saccharum, which blooms a little later 
than Acer negundo. 

It is, however, in the forms with a more complex inflorescence 
that this variation in the time of development reaches the great- 
est degree. Acer platanoides, the next of the common forms 
to open, will show any condition from mature archesporium 
to young pollen grains in the same flower cluster. This renders 
the accumulation of a considerable quantity of material of any 
one stage rather a prolonged task. Maturation occurs during 
the swelling of the bud, and by the time the scales have opened, 
most of the anthers will contain pollen grains. The time for the 
actual flowering of this species is generally the second week in 
April. Acer pseudo-platamis has the largest flower mass of any 
of the commonly grown species, and here development proceeds 
from the base of the raceme toward the tip, with great secondary 
differences in the stage of development of the flowers on the 
secondary racemes. The reduction divisions take place largely 
while the racemes are from 10-15 mm. in length. It flowers 
soon after Acer platanoides. Data for the Japanese and the 
more rarely cultivated European species are incomplete, but 
they mostly flower, in this region, during April or early May. 

It proved much more difficult to get information with regard 
to the time at which the reduction divisions take place in the 
megaspore mother cell. In general it was found that in a flower 
with young microspore tetrads, the megaspore first prophases 
were taking place, while the later phases followed the separation 
of the tetrad. 

Abnormalities in floral structure were not especially sought, 
but some few appeared. With regard to the constancy of the 
dioecious condition in Acer saccharinum and Acer ruhrum it 
should be noted that trees of both species bearing alike male 
and female flowers were found. The flowers occurred in differ- 
ent infloresences on the same twig in Acer saccharinum. Pre- 
dominately male clusters of Acer platanoides often bore a few 



Study of Reproduction in the Genus Acer 117 

flowers, opening later than the others, in which the ovaries 
were normal in appearance. 

Details of abnormalities in the structure of individual flowers 
were not noted, except the occurrence of tri-carpellary ovaries. 
These were found in Acer rubruni, Acer saccharinum, Acer sacc- 
harum, Acer platanoides, and Acer pseudo-platanus, the forms 
in which quantities of female material underwent close exam- 
ination. 

Pollen Development in Acer Negundo 

The early stages in the development of the anther and the 
origin of the tapetum and archesporium were not traced. There 
was some variation between the diff'erent species in the number 
of layers forming the wall. An epidermal layer, and an outer- 
most endothecial layer of larger cells were always present. In 
addition inner wall layers were found, varying in number from one 
which disorganized at maturity in Acer spicatum Lam. to three, 
of which one persisted in the mature anther, in Acer pseudo- 
platanus. The tapetum was always strikingly developed. It 
was found to show a multinucleate condition of the cells in all 
of the forms studied, and the nuclear divisions giving rise to this 
state occurred both by a somewhat abnormal looking mitosis 
and by amitotic fission. The latter was by far the commonest, 
and the daughter nuclei often remained attached to each other, 
forming a cluster near the center of the cell. Both began about 
the time of synapsis, and in the mitotic type the number of 
chromosomes appeared in excess of the normal sporophytic 
number (Figs. 31-33)- 

The material at hand has permitted a fairly complete study 
of five species with regard to the details of the reduction divi- 
sions in pollen formation. These are Acer negundo, Acer ruhrum, 
Acer platanoides, Acer pseudo-platanus and Acer saccharum, in 
addition to which fragmentary material of several other forms 
was available. Of these, by far the best quality of material 
came from the first named. The low number of chromosomes 
in this species makes it a verv satisfactory one for study, and 
since the writer found some differences of detail from the descrip- 
tion given by Mottier (13) a synopsis of the stages in Acer ne- 
gundo will precede a comparison with the other forms studied. 



Ii8 Taylor — A Morphological and Cytological 

With the growth of the archesporial cell after the last vege- 
tative division, the chromatic material becomes largely con- 
fined to the nucleolus and only a delicate peripheral linin net- 
work marked by a few chromatic granules can be distinguished 
(Fig. i). With the approaching heterotypic prophase the num- 
ber and size of these granules increase, but there is no sign of 
the paired condition of threads and granules described by Car- 
diff (2). As the leptonema network becomes strongly defined 
the irregularity decreases somewhat, and it passes into synapsis 
in the form of a net, not as a continuous spireme thread (Fig. 3). 
The actuality of synapsis as a condition in the living cell has 
been much questioned, especially by the animal cytologists (11), 
but it is a constant feature in the present material (Fig. 4). 
One thing seems sure, however: the more evidence there is of 
poor fixation, the more the synaptic knot appears as a structure- 
less black mass, and the less as an aggregation of threads. It is 
quite conceivable that still further refinement of technic would 
eliminate it, with consequent abandoning of its emphasis as an 
explanation of various phenomena of inheritance, but the maples 
are so resistant in the walls of their rather small anthers to the 
penetration of fixing fluids that they would form poor material 
on which to base a critical series of experiments. 

From synapsis the spireme emerges in the form of loops (Figs. 
5, 6), which extend to the periphery and result in a very distinct 
hollow spireme (Fig. 7). The figures in this paper difi'er from 
those given by Mottier in the greater delicacy and complexity 
of the thread system, especially at the hollow spireme stage. 
It is probable that this is due to a difference in fixation, and the 
writer feels that the condition here figured is the more represen- 
tative. There is good evidence of anastomosis between the 
strands at this stage, and the longitudinal split present in some 
plants could not be distinguished. 

As shortening of the system during the approach of strep- 
sinema proceeds, it becomes evident that the thick bands that 
are to form the chromosome pairs are formed by the lateral 
approximation of threads (Figs. 8, 9, 10). This opens up the 
controversial question of the nature of the spireme, which has 
recently been admirably presented by E. Digby (6). In a 
general presentation such as this it seems well to withhold a 
discussion of the matter, acknowledging, however, its important 
bearing on current theories. 



Study of Reproduction in the Genus Acer 119 

There is no spiral twisting of the paired threads such as is 
so characteristic of the stage in the Hly (Fig. 11). Instead, they 
break up into a number of segments equal to the reduced chro- 
mosome count. These may appear to collect somewhat to one 
side of the nucleus in a second contraction, but the writer is rather 
inclined to believe that this appearance is in the nature of an 
artifact. The halves of each pair now separate more or less, 
forming very conspicuous rings (Figs. 12, 13), which by separa- 
tion at the ends and contraction give rise to the chromosome 
pairs, seeming to pass through a twisted stage during the short- 
ening. Finally all elements contract to very short rods closely 
associated in pairs lying around the periphery of the nucleus 
(Fig. 14). The number of these is readily counted when few, 
as in this case, but in those forms with many chromosomes, as 
described later, the task becomes much more difficult. 

The nucleolus has from the earliest beginnings of the division 
kept its large size and quality of strongly retaining the stain. 
Although for the most part apparently connected by strands 
with the spireme, the writer would not consider that it con- 
tributed chromatin material by bodily transfer, as has been 
suggested (4), but rather through the intermediary of products 
dissolved in the plasma and which are recombined in the spireme 
into stainable chromatin. This is not an hypothesis readily 
capable of demonstration, but it fits the observed conditions 
better than the other. 

With the approach of diakinesis as described, there appears 
gradually a denser interior cytoplasmic zone surrounding the 
nucleus, which eventually resolves itself into a complex system 
of filaments that show signs of aggregation into sheaves by the 
time the breakdown of the nuclear membrane occurs. At this 
time the cytoplasm rapidly encroaches on the nuclear cavity, 
strands pass into it, and the chromosomes become forced toward 
the center (Fig. 14). The filaments then rapidly swing around 
into a few sheaves showing as a multipolar spindle, and then 
into two in the typical fashion. All this while the nucleolus 
has been rapidly decreasing in size so by the time the bipolar 
condition has been reached, the nucleolus has disappeared 
(Figs. 17, 18). The chromosome pairs then become arranged 
in the nuclear plate, the small rounded elements of each pair 
being directed toward the poles, not lying side by side in the plane 



I20 Taylor — A Morphological and Cytological 

of the equator (Fig. 15). This fact is of importance in connec- 
tion with making the chromosome counts, for in a precise polar 
view it eHminates the likelihood of confusing the count through 
inclusion of both elements of a pair, since the member above 
completely covers and hides from view its homolog below. 

During anaphase the chromosomes pass to the poles as 
small, more or less ovoid bodies (Fig. 16). They are figured 
by Mottier as being elongate, and during the late anaphase as 
showing the split that so frequently is to be observed in plant 
chromosomes at this stage. In the writer's material, the better 
fixed the material appeared, (as judged by lack of shrinkage and 
especially by the wide and even distribution of the chromo- 
somes in the plate), the less the chromosomes appeared elong- 
ated in the anaphase condition. The only elongation that was 
seen appeared to be due to a tendency of some of the chromo- 
somes to stick together, probably a fault of fixation, and this 
increased greatly in material in which clumping of the chromo- 
somes was present. As for the split, that could not be distin- 
guished by the writer in any of the species he examined. It is 
to be noted that these bodies are extremely small: from one- 
half to one micron only in diameter, and the writer has been 
unable after long observation to find evidence of bipartitlon. 

A count of the reduced number at metaphase or early ana- 
phase is readily made in such a species as Acer negundo, which 
fixes well and has a small number of chromosomes. This is for 
the present case given by Darling (4) as thirteen, but in the later 
paper by Mottier (13) this is questioned, twelve being stated 
as the probable number, with, elsewhere, fourteen as an alter- 
native. Why the intermediate count of thirteen should be dis- 
carded when the investigator seems in doubt whether the num- 
ber just above or just below that first given is more correct, the 
present writer fails to see, since there is no especial reason to 
expect an even number for the reduced count. The material 
available for the present paper gave ample clear counts of thir- 
teen to establish this number as the gametophyte chromosome 
count (Figs. 51-56 inch). 

When the chromosomes approach the poles, they tend to 
spread out as flattened structures and to anastomose by projec- 
tions from their edges (Fig. 20). This forms a bowl-shaped 
structure open on the side facing the equator of the spindle 



Study of Reproduction in the Genus Acer 121 

(Fig. 19). The open space is filled with a clearer and less vacuo- 
late plasma than the general neighboring region, clearly differ- 
entiated from the spindle which it terminates. The nuclear 
membrane first becomes evident over the external face of the 
bowl, gradually extending around the sides and contracting the 
open face, accompanied by the chromatin which becomes dis- 
tributed over the entire periphery by the time the membrane 
is complete. The reticulum then rapidly loses its definiteness, 
but it does not seem to pass through a series of comminuting 
stages that are in effect a reversal of the prophase stages. The 
nucleolus in its earliest appearance is difiicult to distinguish 
from the large chromosome-derived bodies, but these stain 
more lightly and become smaller the later the stage studied, 
while the nucleolus gradually becoming larger, can soon be rec- 
ognized (Fig. 21). This nucleolus in many cases seems to be the 
only chromatic body at interkinesis, but deep staining shows 
that there remain angular structures on the periphery about 
equal in number to the chromosomes that went into the nucleus 
(Fig. 22). 

The second or homotypic prophase begins with the estab- 
lishment of dark-staining angular bodies on the nuclear periph- 
ery, seemingly from the centers just mentioned (Fig. 23). As 
these increase in size the nucleolus shrinks, retaining its dark 
staining capacity. They can often be counted, but the contour 
of the nucleus and its small size reduces greatly the number of 
favorable countable cases. After the break-down of the mem- 
brane (Fig. 24) they pass from an irregular distribution into 
the flat plate preparatory to division. The nucleolus, still 
present, passes out from the forming spindle and takes up its 
position w^here the apex of the heterotype spindle had formerly 
been (Fig. 25). It retains its staining capacity up to this point, 
and is a very conspicuous object. The equatorial part of the 
heterotype spindle remains distinct through the homotype divi- 
sion (Fig. 26). The nucleolus disappears suddenly, shrinking 
and paling without evidence of fragmentation. 

The axes of the two homotype spindles may lie in the same 
plane, or in two planes at right angles to each other, or even in 
any intermediate position, thus giving rise to tripartite or cruci- 
ate tetrads, or intermediate forms. 

After separation of the tetrad the elements enlarge consider- 
ably, and each forms its individual wall that, as the pollen grain 



122 Taylor — A Morphological and Cytological 

nears maturity, shows three thin lines which after shedding 
permit the emergence of the pollen tube. The mature pollen 
grain has but two nuclei, the tube and generative nuclei, and 
the latter remains undivided till after the pollen grain has been 
shed. The appearance of the pollen grains of the various spe- 
cies is similar, size being the only evident difference (Fig. 27). 
The pollen grains of anthers in female flowers more often showed 
abnormalities than in anthers of male flowers, and showed de- 
generation as anthesis approached. 

Pollen and Somatic Divisions in Other Species 

The history of pollen development as given for Acer negundo 
is typical in a general way of the genus. The differences ob- 
served in other forms are for the most part those necessary to 
effect the distribution of the larger number of chromosomes. 

Amitosis was the most common form of nuclear division in 
the tapetum cells, but mitotic division was observed in other 
forms than Acer negundo, notably Acer pseudo-platanus. There 
was no special differentiation of the cytoplasm near the spindle 
in Acer negundo, but in Acer saccharum and Acer platanoides 
a denser zone was present, slightly removed from the spindle 
and surrounding it. In Acer rubrum such a dense area was pres- 
ent in a pronounced form, frequently assuming a unilateral or 
unipolar position (Figs. 29, 30). This appearance is hardly 
likely to be an artifact, for the general fixation of the cytoplasm 
and of the chromatin is quite good. In the forms with high 
chromosome numbers there was naturally a greatly increased 
complexity of the spireme at all stages, and especially was this 
true of Acer rubrum. A complete discussion of certain peculi- 
arities of this form are given later, but it is best mentioned 
here that as strepsinema approaches there appears a much more 
decided twiscing of the spireme than was found in Acer negundo 
(Fig. 28). This was true to some extent of the other forms. 
The extreme complexity of the spireme mass prevented a com- 
plete study of Acer rubrum. Certain material of this species 
showed a great deal of abnormality in the pollen grains, described 
later, and in addition to these structural variations in some 
cases delayed division of the nucleus into tube and generative 
nuclei. Division of the generative nucleus within the grain was 
not observed, either as a normal or as an abnormal occurrence. 



Study oj Reproduction in the Genus Acer 123 

In Acer platanoides the reduced number of chromosomes is 
given by Cardiff (2) as eleven. This the writer has been able 
to confirm, although the amount of material available was not 
great (Figs. 59-62). The seeds of this species were germinated 
and the root tips fixed to verify this by making a 2x count. 
Here a word must be recorded with regard to the conditions of 
observation of the mitoses, especially the somatic ones. In all 
of the maples studied the chromosomes in the vegetative parts 
are very small indeed. The longest studied measures about 
three microns in length and the smallest about one micron, 
with in both cases a diameter of from two-thirds to one-third 
micron. Even with good fixation, which with the roots was 
consistently obtained, overlapping of the ends of these bodies, 
and other confusing arrangements frequently occurred. This 
made the interpretation of the complex plates a difficult matter, 
and in the extreme cases of Acer rubrum and an abnormality 
under Acer saccharinum, compels the count arrived at to be 
considered merely as a very careful approximation. The method 
pursued in making all the chromosome counts, both somatic 
and gametophytic, was to draw the most perfect plates with the 
camera lucida at a magnification of 3380 diameters, correct the 
rough sketch by direct observation and recompare under the 
camera before counting. This enabled the writer to be sure no 
element had passed by unobserved. In the cases of small ix 
plates, a few actual drawings were supported by many direct 
observations, readilv made when a small number of elements 
was concerned. With Acer platanoides, having the smallest 
number of chromosomes yet observed in the genus, it was a 
surprise to find that the somatic count obtained in the root tip 
cells did not agree with the reduced count, for the number 
twenty-six was persistently obtained (Figs. 57, 58). A very 
few counts of twenty-five, twenty-seven and twenty-eight prob- 
ably contain observational errors. The difference between the 
observed number and that of twenty-tvvo which was expected, 
is too great to be an error, and indicates probably that there 
exist varieties differing in cytological composition. As no sys- 
tematic attempt was made to keep records of the exact trees 
furnishing the material for each fixation, these features unfor- 
tunately cannot be correlated with the horticultural forms and 
varieties listed by Pax (14). A further feature of this kind 
appeared and will be considered under Acer rubrum. 



124 Taylor — A Morphological and Cytological 

Acer pseudo-platanus was studied with respect to both the 
vegetative and reduced counts, with the result that twenty-six 
and fifty-two were found to be the ix and 2x numbers. The 
root-tips of this species furnished especially favorable material 
for counting, and no significant variations appeared (Figs. 
63-66). 

The Sugar Maple, Acer saccharum, showed few and large 
chromosomes, thirteen being the observed ix number (Figs. 
69-71). 

Only one of the remarkable oriental maples, Acer carpini- 
folium, will be noted here. This has, as the name indicates, 
leaves resembling the Hornbeam, Carpinus. This condition 
made it of interest to obtain a count, and the results indicate 
that fifty-two is the probable somatic number in this case, as 
in the last (Figs. 67, 68). The group was not shown to be 
strikingly different cytologically, therefore, from the forms with 
lobed leaves. 

Because the rapidity with which the pollen maturation of 
the Silver Maple occurred in the fall was unexpected, the writer 
failed to obtain reduction division material that would furnish 
the IX count. In a pollen grain a countable anaphase polar 
view was however obtained, the two plates giving in one case a 
clear twenty-six and in the other a more uncertain twenty- 
seven as the chromosome number (Fig. 73). Germination of 
the seeds gave material for the 2x count, which was determined 
to be between fifty-one and fifty-five, in all probability fifty- 
two as in the preceding cases (Figs. 72, 75). The plates and the 
individual chromosomes of this species are the smallest observed, 
if the number involved is considered. In two roots of this 
form, Acer saccharinum, cases were found where the chromosome 
number, while too great to be exactly determined, approxi- 
mated a 4x condition at metaphase (Fig. 74). Most of the 
plates in these roots were of the normal type, indicating that 
this was an individual cell variation, probably by lack of separa- 
tion of the daughter groups at the metaphase of a former divi- 
sion. A condition believed to be similar, but not so clear, was 
observed in the pedicels of Acer negundo. 

The most perplexing situation presented, however, is that of 
the Red Maple, Acer rubrum. There is but one reference to the 
cytology of this form, a sentence in Mottier's paper on Acer 



Study of Reproduction in the Genus Acer 125 

negundo. He there gives the reduced chromosome count for 
Acer ruhruni as thirty-six, the same as Staphylea. This marked 
the form as strikingly different in nuclear composition from the 
others then known, Acer negundo and Acer platanoides. It was 
early examined by the writer for comparison with the others, 
but the number of chromosomes was so large that with the poor 
fi? ation at first obtained, it seemed impossible to obtain a count. 
With later material better success was attained, and the number 
determined as being between sixty-eight and seventy-five (Figs. 
30, 79-81). This is about twice the number given by Mottier. 
It was not till material of the reduction divisions in the mega- 
spore mother cell was studied that the original count of thirty- 
six was seen (Fig. 34) by the writer. Here a few late prophases 
gave results approximately verifying Mottier. The megaspore 
metaphases were not in such a position that they could be 
counted. This gives a very interesting situation, since the 
pollen material first studied clearly represented a race with a 
2x gametophytic count. As proof of two cytologically distinct 
lines of Acer rubrum this evidence is far more decisive than that 
for Acer platanoides. To add to the interest of the situation 
some material belonging to two other batches was found, which, 
though not as good as that from which the 2x gametophyte 
count was obtained, showed clearly that the reduced number 
of the chromosomes was here in the neighborhood of fifty (Figs. 
82-84). If the original number of thirty-six is exactly correct, 
which, although it seems probable, the writer would not under- 
take to absolutely affirm with the few data at his disposal, 
then seventy-two would be the expected reduced number in the 
tetraploid form. 

The pollen of the material above described probably repre- 
sents such a race. If these hybridized, then the pollen of the 
hybrid form would have a count of fifty-four according to ordi- 
nary expectations, which was observed in one instance in the 
two fixations just mentioned, although most of the counts run 
from fifty to fift>^-two. The seventy-two chromosome class of 
pollen was found in pollen of male flowers, the apparently "hy- 
brid" condition in the pollen of both male and female flowers. 
Unfortunately, such a situation being totally unforseen, no 
records are to be had that would locate the original trees. Meas- 
urements were made to compare the size of the microspore 



126 Taylor — A Morphological and Cytological 

mother cells at the first metaphase. The longest and shortest 
diameters of each grain were taken and averaged for the series. 
The tetraploid material gave an average diameter for those 
counted of 29 microns, the pollen from the "hybrid" male 
flowers gave 23.5 microns, and the pollen from the female "hy- 
brid" 24.8 microns. The difference between these last two is 
hardly significant, being probably a shrinkage variation. The 
volume of the tetraploid cells is therefore about 12,800 cubic 
microns each, and that of the larger "hybrid" material about 
8,000 cubic microns, which gives a ratio somewhat less than 
that of the chromosome numbers, namely 4:2.5 as against 4:3. 
Abnormalities in pollen formation have appeared in Acer 
rubrum, which may throw light on the origin of these conditions. 
In the material giving the intermediate count, one case of a tri- 
polar spindle was found, with the chromosomes partlv oriented 
with respect to one axis, partly with respect to the others. In 
different material pollen grains were found of two sizes inter- 
mixed, in diameter about 39 and 27 microns respectively. Fur- 
thermore, conditions of lack of complete separation of the orig- 
inal tetrad were found, both where, within the wall of the mother 
cell, each of the four had formed a wall of its own and also where 
they remained naked within the common investment. These 
were in anthers where the majority of the pollen grains were 
well advanced toward maturity. Some large grains were present 
with abnormal numbers of nuclei. Germination of the seeds of 
the Red Maple furnished material for a study of the somatic 
divisions, but the extreme complexity of the figures made the 
counting too much of a strain, and, since the accuracy was com- 
parative at best, only a few cases were critically studied. The 
number of chromosomes as counted seemed to be above ninety 
(Figs. 76-78). Owing to the conditions mentioned it would 
be unwise to try to interpret this in terms of the reduced number. 

Ovule Development 

The only maple which has received attention with respect to 
the development of the ovule and embryosac is Acer rubrum, 
upon which Mottier published a paper in 1893 (12). This paper 
was written before some of the most important advances in 
methods of technic, and it was thought advantageous to follow 
the development again in the same species. The observations 



Study of Reproduction in the Genus Acer 127 

of the writer agree for the most part with those of the earlier 
above-named investigator, but there are some points with regard 
to which the writer would like to suggest a somewhat different 
interpretation. To make these clear, a review of the situation 
will be given. 

The ultimate origin of the megaspore mother cell was not 
determined. In material fixed about the end of October, 1918, 
it was already differentiated as a deeply placed cell in the for- 
ward end of the nucellus. The first ovular coat was just becom- 
ing evident at that time (Fig. 85). Little advance in the growth 
occurred till spring, when a rapid increase in size accompanied 
the growth and maturation of the stamens, and the heterotypic 
division in the megaspore mother cell occurred soon after the 
microspore cells had reached the tetrad state. Both of the 
ovular integuments were well developed by the time synapsis was 
reached (Fig. 86). This applies only to the female flowers. 
In the functionally male flowers the ovaries remain very small, 
and the carpels seem to fail to close completely, leaving a rather 
large opening at the stylar end. In the functionally female 
flowers the carpels also remain sufficiently separate at the top 
to leave a pore between the style bases, but this opening was 
filled by the abundant stylar hairs, whose walls seem to become 
partly gelatinized at this point. 

Following the heterotypic division there is formed a wall, 
separating the daughter nuclei into different cells (Fig. 87). 
The writer was able to secure a very complete series of stages 
illustrating the chromatin behavior during the heterotypic divi- 
sion, which was fundamentally similar to the same series in the 
pollen formation. In connection with the discussion of the 
nuclear conditions in this species a megaspore prophase was used 
to illustrate the condition where the reduced chromosome num- 
ber was thirty-six, and the same figure, showing the thirty-six 
paired segments nearing diakinesis, illustrates the difference in 
size between the microspore and megaspore mother cell nuclei 
(Fig. 34). So far there is no question as to the history of the 
megaspore. 

In Mottier's paper the description of the succeeding stages 
is as follows: "The upper cell divides again in a similar manner, 
so that there are three cells resulting from the mother cell (fig. 
5). The lower one of these three now enlarges gradually ab- 



128 Taylor — A Morphological and Cytological 

sorbing the two upper; its large nucleus soon divides, and the 
resulting nuclei move away from each other toward the opposite 
ends of the cell (fig. 5). The further behavior of these nuclei 
is similar to that which obtains in all known embryosacs of 
angiosperms." From his figures it seems evident that the "upper 
cell" means the one near the micropyle, and the "lower cell" 
the one near the chalaza. His description would indicate that 
the more micropylar cell goes through the homotypic division 
before there is any division in the more chalazal cell, and that 
following this division a wall is laid down and then the two cells 
thus formed degenerate. The homotypic division in the chala- 
zal cell of the pair then follows, and both of the nuclei formed 
function in the maturation of the embryosac, each dividing 
twice to give the eight elements of the mature sac. It appeared 
to the writer an unusual circumstance that one cell of the orig- 
inal diad should go through a complete homotypic division 
only to degenerate, whereas in the other the nucleus only should 
divide and both nuclei function. In view of the more recent 
work in cytology it seems more to be expected that one of the 
cells of the original diad should degenerate without dividing, 
and that if the homotypic division in the other cell closed with 
wall formation, the daughter cell adjoining the degenerating 
cell should also break down. This would account for the two 
degenerating cells reported by Mottier, and would indicate 
that the nucleus in the remaining cell, morphologically equiva- 
lent to one cell of a tetrad, would have to pass through three 
successive free gametophytic divisions before the embryosac 
reached maturity, which is rather the normal history in dicoty- 
ledons. However, if Mottier actually saw the process of divi- 
sion of the micropylar cell of the diad, this history could not 
hold. But he does not figure any stage during the division, 
and it is easily possible to misinterpret the condition if only the 
final product of a row of three cells is available. The significant 
difference between the two possibilities lies in that in the one 
case only two gametophytic divisions occur, showing a tendency 
toward the Lilium type where but one is present, while in the 
second case the more normal number of three would be found. 
The question as to whether a cell which is to undergo degenera- 
tion is likely to divide earlier and in a more primitive manner 
{i. e., with wall formation) than its sister cell which is to 



Study of Reproduction in the Genus Acer 129 

function, also deserves consideration. Such material as the 
writer has favors the interpretation here offered, but it is not 
sufficiently conclusive to serve as a basis for discarding the state- 
ment of Mottier, and thequestion must be left open for the present. 

In any event, by the time the row of three cells is formed, 
the ovule begins to bend downward, and the outer integument 
on the lower side of the ovule begins to enlarge decidedly (Fig. 
88). By the time the chalazal cell of the row of three has under- 
gone the first division the ovule has increased greatly in size, 
bent over nearly as far as it ever does, and it is evident that the 
degeneration of the two cells at the micropylar end of the row 
of three is far advanced. From the swelling of the outer integu- 
ment the cells grow as hair-like processes (Fig. 89). The divi- 
sion into the four nucleate stage shows these hair cells even more 
elongate, and beginning to become crowded at the bottom of 
the ovarian cavity (Fig. 90). They subsequently form a mass 
of considerable size, and about the time of fertilization their 
walls seem to be thickened in a gelatinous manner, and evidences 
are present that the cavltv of the ovary contains a partly coag- 
ulable liquid. The hairs may secrete a fluid which aids in the 
passage of the pollen tube to the micropyle. 

There is rarely any evidence of the degenerating cells bv the 
time the eight nucleate stage of the embryosac has been reached. 
Of these eight nuclei, three pass to the antipodal end and or- 
ganize cells the membrane of which often is very indefinite. 
Two form synergida? and one an egg at the micropylar end, 
the latter protruding into the embryosac cavity above the 
synergidae. Two nuclei remain, one at each end of the sac 
(Fig. 36). These polar nuclei pass toward the center of the 
cavity, where they come into contact (Fig. 37), and then pass 
together to the egg, usually not fusing till they have taken up 
a position close above it (Figs. 38, 39). Fusion is by simple 
merging of the contents, no definite spireme being in evidence 
at this time (8). This stage is generally not reached till after 
the flowers have opened, and even till after pollination has taken 
place. The antipodal cells very soon disappear, though thev 
mav in occasional cases persist for some time (3). 

Fertilization and Embryogeny 
The fusion of the gametes in Acer, so far as observed, re- 
sembles the conditions described bv Ishikawa for Oenothera (8). 
The pollen tube in entering destroys usuallv only one of the 



130 Taylor — A Morphological and Cytological 

synergidae, the other persisting for a short time (Fig. 40). The 
"filiform apparatus" was very sHghtly developed. As the flow- 
ering of Acer saccharinum upon which the writer had counted 
for the sequence of stages succeeding the entrance of the sperm 
nuclei, was followed in 1919 by a severe frost and most of the 
ovules rendered abnormal or infertile, a detailed discussion of 
the stages in fertilization will be held for another paper. As 
soon as the triple fusion is accomplished the endosperm nucleus 
passes up to the middle of the embryosac (Fig. 40). Division 
does not ordinarily take place till this position is reached (Fig. 
42). The fertilized egg is even slower to divide, usually holding 
back till the eight or even the sixteen nucleate stage of the endo- 
sperm. The first wall is transverse (Fig. 41), and so is the 
second, but the third is vertical or oblique in the terminal cell 
(Fig. 43), and is followed by a similar wall in the middle cell of 
the original row (Fig. 44). The basal cell seems to divide once 
more (Figs. 45, 46), and in the later development of the embryo 
may divide a few times to give the irregular group of cells which 
form the suspensor of the embryo. The endosperm never be- 
comes more than a sheath of protoplasm in which the free nuclei 
divide, at first by mitosis, and later amitotically. They become 
very numerous, reaching many hundreds. The cavity of the 
embryosac increases greatly after fertilization, and the nucellus 
stretches to accommodate it. This condition is especially 
marked in Acer saccharinum and Acer platanoides. In the 
latter the contents of the nucellar cells appear disintegrated, 
and the walls themselves later in part break down, so that by 
the time the embryo has reached the stage of the Red Maple 
embryo shown in Fig. 47, the cavity of the embryosac will have 
increased in volume a hundred times, and be surrounded by 
only a very few layers of stretched nucellar cells, except just 
above the micropyle, where the stretching and disintegration 
does not occur. The embryo occupies only a very small part 
of the pointed micropylar end of this cavity, and the rapid growth 
of the sac and disintegration of the nucellus is therefore not due 
to pressure from the embryo. The outer part of the second 
integument becomes hardened, protecting the embryo, especially 
in some of the exotic forms. The rapid growth of the embryo, 
though delayed, causes the cotyledons in many species to become 
crumpled in the seed. Evidence of the beginning of this con- 



Study of Reproduction in the Genus Acer 131 

dition appears long before the length of the embryo equals that 
of the cavity, in Acer rubruni. The form of the embryo differs 
somewhat among the various species even in the early stages 
(Figs. 49, 50). 

In most species the ovary did not grow much faster than 
necessary to accommodate the swelling ovules, but in others, 
Acer negundo especially, immediately after fertilization the 
ovarian cavity increased at a much greater rate than the ovules. 
The growth of the alae is initiated by pollination, progressing 
far before development of the embryo begins. Fertilization 
seems to take place about forty to seventy-two hours after 
pollination. 

Abnormalities in embryosac development were many. It is 
to be remembered that of the two ovules formed in each cavity 
of the ovary only one comes to maturity, and that even in the 
flowers that are developing normally half the embryosacs seen 
will be in stages of abnormal development or degeneration. 
The presence of sterile flowers increases the number of atypical 
cases. The frost mentioned above seemed to destroy the egg 
first, so that a several-nucleate endosperm with a shriveling egg, 
as well as other degenerate conditions, was found in material 
gathered on the days succeeding the cold spell. 

In one ovule of Acer platanoides an embryosac with a double 
embryo appeared. The second appeared as a smaller individual, 
attached to the base of the primary one. It possibly resulted 
from a bifurcation of the head end of the embryo while small, 
after which one of the halves greatly out-grew the other (Figs. 
91, 92). 

Seedling Anatomy 

A study of the anatomy of the developing Maple seedling 
offers little of itself, but a comparison of the normal with a 
tricotyledonous specimen which sprouted in one of the cul- 
tures is of interest. The development in maples of specimens 
with abnormal numbers of cotyledons and of later leaves in 
whorls of three or even more is well known (15) as is also twin- 
ning, etc. (5). 

In Acer rubrum the cotyledons have in the contracted lower 
part of the blade about six vascular strands (Fig. 93). These 
unite in the petiolar part to two (Figs. 94, 95) which pass un- 
fused into the hypocotyl (Figs. 95, 96). The plumule at first 



132 Taylor — A Morphological and Cytological 

shows only one strand in each leaf, but as they grow three be- 
come evident which fuse in the petioles or, lower, in the hypo- 
cotyl (Figs. 94, 95). The bundles which supply the plumule 
become less and less prominent as one descends the axis, the 
xylem disappearing and the phloem fusing laterally with the 
adjacent bundles supplying the cotyledons (Figs. 96, 97), till 
at last there is a simple axis with four collateral bundles (Fig. 
98). These form the four poles of the tetrarch root by simple 
rotation of the elements (Figs. 99, 100, loi). 

In the same species the tricotyledonous specimen was pre- 
pared in serial sections, and the vascular strands traced in the 
same way. In the upper part of the cotyledons there were about 
the same number of vascular strands as in the cotyledons of the 
normal form. Toward the petiolar base in two of them the 
strands partially united (Figs. 102, 103), to reappear again in 
the hypocotyl as two distinct but closely placed bundles (Fig. 
104). The third cotyledon possessed a small lobe near the 
base (Fig. 102) which united with it before union with the axis 
occurred. In this case the two bundles at the base remained 
widely separated, a small patch of phloem tissue remaining 
between them (Figs. 103, 104). There were three plumular 
leaves, all prominently three-lobed. These had each three vas- 
cular strands, which remained distinct into the hypocotyl, where 
the xylem of the lateral members of each group disappeared, 
and the phloem of these fused with the central member (Figs. 
102, 103, 104). Instead of becoming united into four bundles 
in the upper hypocotyl as in the normal specimens, the bundles 
from cotyledons and plumule formed an irregular ring (Fig. 105). 
A bend above the base of the hypocotyl made it impossible to 
determine whether these fused to a regular number in the lower 
hypocotyl, or, as seems likely from the irregular distribution of 
the xylem (Fig. 106), merged in the transition zone at the base 
of the hypocotyl. There the vascular system appeared as an 
irregular ring, the xylem elements on the inner margin. In the 
top of the root these passed out toward the periphery at four 
points (Fig. 107) forming a tetrarch root that was somewhat 
more irregular in form than the normal (Fig. 108). 

The condition indicated seems to be that of a simple fission 
of one of the two typical cotyledons carried to its greatest extent, 
the bundles supplying each part being distinct far down the 



Study of Reproduction in the Genus Acer 133 

hypocotyl. The small lobe at the base of the third cotyledon 
may or may not represent a partial development of the same 
kind. 

Summary 

The Maples studied, with one exception, Acer saccharinum, 
mature their pollen during the expansion of the buds in the 
spring. Acer saccharinum matures its grains to the one nucle- 
ate stage in the autumn, the division to form the tube and gen- 
erative nuclei generally being delayed till shortly before flower- 
ing. It is the first of the genus to bloom, being followed at inter- 
vals by the other native forms, the exotic species closing the 
series about the end of April. 

Pollen development in Acer negundo proceeds much as de- 
scribed by Mottier, and in the other Maples studied the process 
is similar. The haploid chromosome number is thirteen. Hap- 
loid counts were made in Acer platanoides showing eleven, in 
Acer saccharum showing thirteen, in Acer pseudo-platanus show- 
ing twenty-six, in Acer saccharinum showing twenty-six, and 
in Acer rubrum showing approximately seventy-two, fifty-four 
and (megaspore mother cell) thirty-six chromosomes. 

Somatic counts were made in the root-tips of some species 
with the following results: Acer platanoides, twenty-six; Acer 
pseudo-platanus, fifty-two; Acer saccharinum, fifty-two, with also 
isolated cells containing about twice that nnvaher ; Acer carpinifo- 
lium, Mty-t'wo;a.nd Acer rubrum, above ninety. The difference be- 
tween the somatic and reduced counts in Acer platanoides mav be 
due to differing strains with diflfering nuclear composition. The 
conditions in Acer rubrum seem to indicate that a tetraploid 
form exists, and the intermediate counts similarly seem to indi- 
cate that hybrids with the normal diploid form occur. 

Ovule development was followed in Acer rubrum and other 
species, with in the species named a row of three potential 
megaspores resulting from the divisions of the mother cell. The 
chalazal one persists, the other two degenerate. The persistent 
cell gives rise to the embryosac, which is normal with eight 
nuclei. The polar nuclei fuse before fertilization and the endo- 
sperm nucleus passes to the middle of the sac before dividing. 
The embryosac enlarges greatly, especially in Acer platanoides, 
and many free endosperm nuclei are produced, but no cell walls 
are laid down. The growth of the embryo does not accompany 



134 Taylor — A Morphological and Cytological 

that of the ovular cavity, but is at first delayed, later progress- 
ing more rapidly so as to fill the cavity often with accompany- 
ing crumpling of the cotyledons. 

Abnormalities of pollen formation, such as giant grains and 
unseparated tetrads, were seen, and also abnormalities in the 
formation of the embryosac. Tricarpellary ovaries appeared 
in several forms, and a twin embryo was observed, with one 
individual much larger than the other. 

Bibliography 

1. Allen, Charles E. The Basis of Sex Inheritance in Sphcerocarpos. 

Proc. Amer. Phil. Soc, Vol. LVIII, p. 289. 1919. 

2. Cardiff, Ira D. A Study of Synapsis and Reduction. Bull. Torrey 

Bot. Club, Vol. 33, p. 271. 1906. 

3. Coulter and Chamberlain. Morphology of Angiosperms. 1912. 

4. Darling, Chester A. Sex in Dia?cious Plants. Bull. Torrey Bot. 

Club, Vol. 36, p. 177. 1909. 

5. DeVries, Hugo. Mutation Theory. Vol. II. 191 1. 

6. DiGBY, L. On the Archesporial and Meiotic Divisions of Osmunda. 

Ann. Bot., Vol. XXXIII, p. 135. 1919. 

7. Goebel. Outlines of Classification and Special Morphology. English 

Translation. 1889. 

8. IsHiKAWA, Rigakushi, M. Studies on the Embryosac and Fertilization 

in Oenothera. Ann. Bot., Vol. XXXII, p. 279. 1918. 

9. Kanda, M. Field and Laboratory Studies of Verbena. Bot. Gaz., 

Vol. LXIX, p. 54. 1920. 

10. Mackenzie, Marion. Phytophenology in its Application to the Plants 

of the Philadelphia Neighborhood. Trans. Bot. Soc. Penna., Vol. II, 
p. 288. 

11. McClung, C. E. Spermatocyte Divisions of the Acrididce. Kansas 

University Quarterly, Vol. IX, p. 73. 1900. 

12. MoTTiER, D. M. Development of the Embryosac of Acer rubrum. Bot. 

Gaz., Vol. XVIII, p. 375- 1893. 

13. MoTTiER, D. M. Mitoses in the Pollen Mother Cells of Acer negundo L. 

and Staphylea trifoliata L. Ann. Bot., Vol. XXVIII, p. 115. 1914. 

14. Pax, F. Aceraceae in "Das Pflanzenreich", 8 Heft. (IV. 163). 

15. Thisleton-Dyer, Sir W. T. Morphological Notes. Ann. Bot., Vol. 

XVI, p. 554. 1902. 

Explanation of Plates 

Plate VI — Stages in Reduction Divisions, Pollen Formation in Acer negundo. 
h\\ Figures Reproduced X2250. 
Fig. I. Resting nucleus after last archesporial division. 
Fig. 2. Nucleus showing approaching leptonema. 



Study of Reproduction in the Genus Acer 135 

Fig. 3. Leptonema entering synapsis as a network. 

Fig. 4. Mid-synapsis. 

Fig. 5. Looped pachynema threads leaving synapsis. 

Fig. 6. Ditto. 

Fig. 7. Hollow spireme. 

Fig. 8. Contracting hollow spireme passing into strepsinema. 

Fig. 9. Early strepsinema. 

Fig. ID. Strepsinema, thread breaking up. 

Fig. II. Strepsinema, thread largely broken into chromosome segments. 

Fig. 12. Ring-like chromosome segments. 

Fig. 13. Ditto. 

Fig. 14. Breakdown of the nuclear membrane, strands of cytoplasm 
traversing the cavity. 

Fig. 15. Polar view, heterotypic metaphase, showing thirteen chromo- 
somes, haploid number. 

Fig. 16. Side View, heterotypic anaphase. 

Plate VII — Stages in Reduction Divisions, Pollen Formation in Acer negundo 
(Figs. 17-26), Acer rubrum (Figs. 28-30), and Pollen Grain of Acer 
saccharinum (Fig. 27). All except Fig. 27 reproduced X2250. 

Fig. 17. Multipolar spindle, early with large nucleolus. 

Fig. 18. Multipolar spindle, later, with smaller nucleolus (in center). 

Fig. 19. Side view, telophase of heterotypic division. 

Fig. 20. Polar view, telophase of heterotypic division, showing thirteen 
chromosomes. 

Fig. 21. Late telophase, showing formation of nucleolus, the large body 
in center of nucleus. 

Fig. 22. Nucleus during interkinesis. 

Fig. 23. Prophase of homotypic division. 

Fig. 24. Polar view, breakdown of nuclearmembrane, homotypic divi- 
sion, nucleolus evident. 

Fig. 25. Multipolar spindle, homotypic division, showing the remains of 
the homotypic spindle, and the nucleoli near the periphery of the cell. 

Fig. 26. Homotypic division, side and polar views, showing remains of 
heterotypic spindle and thirteen chromosomes in the polar view of the 
metaphase. 

Fig. 27. Pollen grain, mature state, with tube and generative nuclei, 
Acer saccharinum. X950. 

Fig. 28. Strepsinema, Acer rubriim. 

Fig. 29. Side view, heterotypic metaphase, showing chromosome pairs 
and polar position of the dense mass of cytoplasm. Seventy-two 
chromosome form. 

Fig. 30. Polar view, heterotypic metaphase, showing lateral position 
of the dense cytoplasmic mass. Shows count of seventy-two chromo- 
somes. 

Plate VIII — Tapetal Cells of Acer negundo (Figs. 31-33), Embryosac and 
Embryo Formation in Acer rubrum (Figs. 34-41, 43-49), Embryosac 
and Embryo of Acer saccharmum (Figs. 42, 50). Reproduced X200, 
except as indicated. 



136 Taylor — A Morphological and Cytological 

Fig. 31. Tapetum cells, showing amitotic nuclear division. X900. 

Fig. 32. Ditto. X900. 

Fig- 33- Tapetum cells, showing mitotic nuclear division. X900. 

Fig. 34. Megaspore mother cell, early diakinesis, showing about thirty- 
six chromosome pairs. X2250. 

Fig. 35. Row of three megaspores, micropylar pair degenerating, chalazal 
undergoing nuclear division. 

Fig. 36. Embryosac before migration of the polar nuclei to the center 
of the embryosac. 

Fig. 37. Meeting of the polar nuclei at the center. 

Fig. 38. Fusion of the polar nuclei after reaching the egg. The nuclear 
membranes between the nuclei have disappeared. X470. 

Fig. 39. Mature embryosac ready for fertilization. 

Fig. 40. Embryosac shortly after fertilization. One of the synergidae 
has been destroyed, the other is disintegrating but the nucleus is evi- 
dent. The dark mass introduced by the pollen tube is present, and 
the endosperm nucleus has begun to move toward the center of the em- 
bryosac. 

Fig. 41. Two cell stage of the embryo, eight nucleate endosperm. 

Fig. 42. Fertilized embryosac before division of endosperm nucleus. 

Fig. 43. Four-celled embryo. 

Fig. 44. Five-celled embryo. 

Fig. 4.S. Nine-celled embryo. 

Fig. 46. Eight (?) celled embryo. 

Fig. 47. Older embryo. 

Fig. 48. Embryo showing beginning of the two cotyledons. X25. 

Fig. 49. Older embryo of Acer rubrum. X25. 

Fig. 50. Older embryo of Acer saccharinum. X25. 

Plate IX — Chromosome Counts in Various Maples. All figures repro- 
duced X2250. 

Fig. 51. Upper and lower groups, heterotypic anaphase in Acer negundo. 
Thirteen chromosomes in each case. 

Fig. 52. Metaphase plate, homotypic division, Acer negundo, showing 
thirteen chromosomes. 

Fig. 53. Ditto, another case. 

Fig. 54. Metaphase plate, heterotypic division, Acer negundo, showing 
thirteen chromosomes. 

Fig. 55. Ditto, another case. 

Fig. 56. Ditto, another case. 

Fig. 57. Metaphase plate, division in root-tip, Acer plalanoides, showing 
twenty-six chromosomes. 

Fig. 58. Ditto, another case. 

Fig. 59. Metaphase plate, heterotypic division, Acer plalanoides, show- 
ing eleven chromosomes. 

Fig. 60. Ditto, another case. 

Fig. 61. Anaphase group, heterotypic mitosis, Acer plalanoides, showing 
eleven chromosomes. 

Fig. 62. Ditto, the other group from the same cell. 



Study of Reproduction in the Genus Acer 137 

Fig. 63. Metaphase plate, division in root-tip cell, Acer pseudoplatanus, 

showing fifty-two chromosomes. 
Fig. 64. Ditto, another case. 
Fig. 65. Metaphase plate, heterotypic division, Acer pseudo-plalanus, 

showing twenty-six chromosomes. 
Fig. 66. Ditto, another case. 
Fig. 67. Metaphase plate, division in root-tip cell, Acer car pini folium, 

showing apparently fifty-five chromosomes. 
Fig. 68. Ditto, another case, with the more frequently found number of 

fifty-two chromosomes. 
Fig. 69. Metaphase plate, heterotypic division, Acer sacchartim, showing 

thirteen chromosomes. 
Fig. 70. Anaphase plate, heterotypic division, Acer saccharum, showing 

twelve chromosomes. 
Fig. 71. Ditto, other plate in small cell, showing thirteen chromosomes. 
Fig. 72. Metaphase plate, division in root-tip cell, Acer saccharinum, 

showing fifty-two chromosomes. 
Fig. y;^. Anaphase groups, division in pollen grain to form tube and 

generative nuclei, Acer saccharinum, showing twenty-six and (?) 

twenty-seven chromosomes. 
Fig. 74. Metaphase plate, division in root-tip cell, Acer saccharinum, 

showing ninety-one (or more) chromosomes, approaching twice the 

normal number. 
Fig. 75. Ditto, ordinary cell, showing fifty-two chromosomes. 
Fig. 76. Metaphase plate, division in root-tip cell, Acer rubrum, showing 

ninety (or more) chromosomes. 
Fig. 77. Ditto, showing eighty-eight (or more) chromosomes. 
Fig. 78. Ditto, showing ninety-four (or more) chromosomes. f 

Plate X — Chromosome Counts and Ovule Development in Acer rubrum, 
Abnormal Embryo in Acer platanoides (Figs. 79-84 X2250, Figs. 
85-90 XI35)- 

Fig. 79. Metaphase plate, heterotypic division, showing seventy chro- 
mosomes. 

Fig. 80. Ditto, showing sixty-eight chromosomes. 

Fig. 81. Ditto, showing sixty-seven chromosomes. 

Fig. 82. Ditto, showing fifty-three chromosomes. 

Fig. 83. Ditto, showing fifty-four chromosomes. 

Fig. 84. Anaphase groups, heterotypic division, showing fifty-two and 
forty-eight chromosomes. 

Fig. 85. Ovule, resting condition in late autumn. 

Fig. 86. Ditto, at time of synapsis. 

Fig. 87. Ditto, after heterotypic division, showing two cells derived from 
megaspore mother cell. 

Fig. 88. Ditto, showing row of three potential megaspores. 

Fig. 89. Ditto, showing micropylar two in row degenerating, chala^al 
cell in the two nucleate stage of the embryo-sac. 

Fig. 90. Ditto, embryosac cell in four nucleate stage. 



138 Taylor — A Morphological and Cytological 

Fig. 91. Twin Embryo, Acer platanoides, showing cells of the smaller 

embryo. X200. 
Fig. 92. Ditto, showing attachment region of the embryos. X200. 

Plate XI — Dicotyledonous and Tricotyledonous Seedling Structure in Acer 

rubrum. All Figures X30. 
Fig. 93. Dicotyledonous seedling section through lower part of blade of 

cotyledons. 
Fig. 94. Ditto, section through upper part of cotyledonary petioles. 
Fig. 95. Ditto, through junction of cotyledons with hypocotyl. 
Fig. 96. Ditto, just below cotyledonary node. 
Fig. 97. Ditto, a little lower than Fig. 96. 
Fig. 98. Ditto, through middle region of hypocotyl. 
Fig. 99. Ditto, at top of transition region near base of the hypocotyl, 

showing bundle ring. 
Fig. 100. Ditto, lower, showing passage of xylem toward the periphery 

at four points, in the top of the root. 
Fig. loi. Ditto, lower, in main root axis, showing tetrarch character. 
Fig. 102. Tricotyledonous embryo, section through lower part of blade 

of cotyledons. 
Fig. 103. Ditto, through junction of cotyledons with hypocotyl. 
Fig. 104. Ditto, just below cotyledonary node. 
Fig. 105. Ditto, through middle region of hypocotyl. 
Fig. 106. Ditto, through top of transition region near base of the hypo- 
cotyl, showing bundle ring. 
Fig. 107. Ditto, lower, showing passage of xylem toward the periphery at 

four points, in the top of the root. 
Fig. 108. Ditto, lower, in main root axis, showing irregular tetrarch 

structure. 

Note — All drawings of cytological details except stages in the develop- 
ment of the embryosac were drawn at a magnification of 3,380 diameters. 
Other details were drawn at lesser magnifications, and all figures except those 
on Plate XI have been reduced in reproduction to two-thirds of the original 
size. The figures of seedUng structure were drawn at 75 diameters and re- 
duced to 30 diameters in reproduction. 



THE MORPHOLOGICAL CONTINUITY OF 
SCROPHULARIACEAE AND OROBANCHACEAE 

BY 

IRWIN BOESHORE, B. S., Ph. D. 

With Plates XII-XVI. 

(Thesis presented to the Faculty of the Graduate School in 

PARTIAL fulfilment OF THE REQUIREMENTS FOR THE DEGREE 

OF Doctor of Philosophy.) 
CONTENTS 



Introduction 139 

Review of Previous Literature and Discussion 141 

General Morphology of the Root 147 

Histology of the Root 150 

Comparative Morphology and Physiology of Stem and Leaf 153 

Comparative Study of the Inflorescence 160 

Comparative Study of the Flower 161 

The Calyx 161 

The Stamens 164 

The Pistil 167 

The Ovary 167 

Hairs of the Pistil 167 

The Nectary 168 

The Seeds 169 

Selection of Hosts 1 70 

Summary. 171 

Conclusions 174 

Explanation of Plates 175 

Literature cited 1 76 



139 



140 Boeshore — The Morphological Continuity of 



Introduction 

In the past, the genera of Orobanchaceae have been regarded 
as of nearest affinities with the Gesneraceae; this wholly because 
of the one-celled ovary. But such a proceeding only takes ac- 
count of one morphological detail. Is there any other family 
with which Orobanchaceae can be directly and continuously 
connected in many morphological features? The group, being 
wholly parasitic, must of necessity be derived as an offshoot from 
some family wholly free or more or less parasitic in habit. 

The only related family showing such is Scrophulariaceae. 
While the majority of these in genera are green and independent 
in their nutrition, others show all stages in degradation-transi- 
tions to reduced green root parasites, thence to yellowish, or 
red-yellow parasites, finally to degraded simplified parasites 
that are wholly heterotrophic {Harveya, Hyobanche). Thus, for 
example, in the single genus Gerardia of the Eastern United 
States some species are tall leafy plants, as in G. flava, and these 
show slight root parasitism. Transitions can be traced from 
this to G. pedicularia, thence to G. purpurea, to G. oligophylla, 
and to G. aphylla, the last of which has scant twigs and small 
leaves that may be almost absorbed. The flowers in the latter 
are few and reduced in size, while parasitism is almost complete- 
ly established in relation to other plants. From such forms 
transition is easy and gradual to Striga, Harveya, and Hyobanche. 
But between Harveya and G. aphylla on the one hand, or species 
of Orohanche on the other, the macroscopic and microscopic 
resemblances, as will afterward be shown in this paper, are grad- 
ed and complete. Is then the fundamental resemblance to 
Gesneraceae of a one-celled ovary as compared with Scrophular- 
iaceae with its two-celled ovary fundamental and indicative of 
true affinity? This question will be fully worked out in a later 
part of the paper. But attention might now be drawn to eome 
comparative morphological facts that may shed light on the 
present problem. 

If we review the more pronounced saprophytic families of 
flowering plants, like Burmanniaceae, Orchidaceae, Ericaceae, 
(including Monotropaceae) and Gentianaceae, all show degra- 



Scrophulariaceae and Orobanchaceae 141 

dation-transitions from green strongly vegetative plants of in- 
dependent nutrition, to others with feeble root saprophytism 
and thence to highly degraded colorless and heterotrophic plants 
like Thismia of Burmanniaceae, colorless genera like Epipogon, 
Aphyllorchis, Neottia, and Corallorhiza in Orchidaceae, color- 
less Monotropa and other genera of the Ericaceae, and the color- 
less Leiphaimos in Gentianaceae. Now in all of these, distinct 
and continuous transition is seen from five-celled, three-celled, 
or two-celled states (Ericaceae, Burmanniaceae, Orchidaceae, 
two-celled Gentianaceae) of the ovary to incompletely five-three 
or two-celled, and ultimately a one-celled state with parietal 
placentation. Such might, therefore, suggest that Orobanch- 
aceae simply represents a greatly degraded offshoot series or 
sub-family of parasitic habit that has gradually been derived 
from Scrophulariaceae in which slow absorption of the ovarian 
partitions has resulted in a one-celled state from a primitively 
two-celled. If such be true, then varied morphological trans- 
sitional characters should be traceable between Scrophular- 
iaceae and Orobanchaceae, while correlated with this a graded 
physiological parasitism and degradation should also be observ- 
ed. It is the aim of the present thesis to demonstrate that such 
is correct. 

In undertaking this, the writer might first review the varied 
opinions held by previous observers. 

Review of Literature and Discussion 

Wettstein (i, p. 48) separates the Scrophulariaceae from the 
Orobanchaceae and Gesneraceae on account of the one-celled 
ovary in the last two. He states that a great many Scrophu- 
lariaceae have close affinities with other families. "Die Orobanch- 
aceae und Gesneriaceae lassen sich durch den i facherigen Frkn, 
mit parietaler Placentation .... von den Scrophular- 
iaceae unterscheiden. " He then states that clear connections 
are shown in the genera Harveya, Hyobanche, and Buchnera of 
Scrophulariaceae with Orobanchaceae. 

Beck (2, p. 128) makes this statement: "The Orobanchaceae, 
which are frequently regarded as a parasitic side line of the Ges- 
neraceae, are separated from the Gesneraceae through the per- 
fect superior fruit, from the Cyrtandreae through the richly de- 



142 Boeshore — The Morphological Continuity of 

veloped endosperm and the undeveloped endosperm of the seed 
. . . . from both especially through their parasitism. 
The one-celled fruit separates them from the Scrophulariaceae 
with which they have also much in common." (Present Au- 
thor's Trans.) 

Fritsch (3, p. 141) under the Gesneraceae treats the connec- 
tions of Gesneraceae with related families, especially with the 
Scrophulariaceae, Orobanchaceae and Bignoniaceae, and holds 
that a sharp distinction can scarcely be drawn between these 
families. He further says, "Hingegen stehen die Orobancha- 
ceae den Gesneraceae so nahe, dass die Auffassung derselben als 
einer parasitischen, laubblattlosen Unterabteilung der Gesner- 
iaceae keinen grossen Fehler involvieren diirfte. Immerhin ist 
die Placentation und der Bau des Frkn. iiberhaupt ein Unter- 
scheidungsmal zwischen den Gesneriaceae, Orobanchaceae und 
Scrophulariaceae. " 

Baillon (4) makes no comparison of the Scrophulariaceae with 
the Gesneraceae and Orobanchaceae. He does not consider the 
Gesneraceae and Orobanchaceae as two separate families, but 
regards the Orobanchaceae (of other authors) as a parasitic ser- 
ies of the Gesneraceae. 

LeMaout and Decaisne (5, p. 593) include the genus Hyo- 
hanche in the Orobanchaceae, though on account of its two-celled 
ovary, most authors place it in the Scrophulariaceae. The fol- 
lowing is stated: "Orobanchaceae approach the Scrophulari- 
aceae in their regular corolla, didynamous stamens, capsular 
fruit, and albuminous embryo; they differ in their leafless and 
scaly stem and parietal placentation. This placentation, their 
glandular disk, and the preceding characters ally them to Ges- 
neraceae, from which they are separated by their scattered 
scales, parasitism, hypogynous corolla, and basilar embryo." 

Warming (6, p. 525-28) places Lathraea in the family of Scro- 
phulariaceae. The plant is described as pale yellow, or reddish 
(without chlorophyll) ; it is parasitic on the roots of the Hazel, 
Beech, and other shrubs or trees, having an aerial stem, and an 
underground perennial rhizome ,covered with opposite, scale- 
like, more or less fleshy leaves. It approaches Gesneraceae in 
having a unilocular ovary with two parietal placentae. With 
him Orobanchaceae finds no place as a family, the genus Oroban- 
che being included in the Gesneraceae. "Orobanche (Broom- 
rape) is allied to this order as a parasitic form." 



Scrophulariaceae and Orobanchaceae 143 

Perhaps the most extensive morphological and physiological 
studies of parasitic Scrophulariaceae and Orobanchaceae have 
been made by Heinricher (7, p. 390-451, 665-773) and Solms- 
Laubach (8, p. 560-75) on the former, by Beck (9, p. 7-70) and 
Koch (10,) on the latter. The work on such genera as 
Euphrasia, Odontites, Pedicularis and not least Bartsia and 
Tozzia, by Heinricher has a very definite bearing on the present 
investigation. To quote from him on Bartsia and Tozzia: "In 
der That sind es diese beiden Rhinanthaceen, welche uns die 
Briicke von den halbparasitischen Rhinanthaceen zu der holo- 
parasitischen Gattung Lathraea bauen. . . . Der Aufbau 
des Lathraea- Rhizoms ahnelt sehr dem von Bartsia, die Unter- 
schiede sind wesentlich dadurch bedingt, das erstere H0I0-, 

letztere Hemiparasit ist Tozzia nimmt eine 

ganz eigene Stellung in der Rhinanthaceen-Rheihe ein; sie ist 
nicht Holoparasit und nicht Hemiparasit, sondern sie ist beides 
in zeitlicher Folge. Und so wird sie eben zum biologischen 
Bindeglied Zwischen den Halbschmarotzern und der Holopara- 
sitischen Gattung Lathraea.'' 

In view of the above comparative estimates of different au- 
thors, the question at issue resolves itself into one of three po- 
sitions, (i) The Gesneraceae and Orobanchaceae are most 
nearly related to each other in that they both possess a one-celled 
ovary with deep to shallow parietal placentation. (2) Oro- 
banchaceae and Scrophulariaceae are most nearly related to each 
other in their root parasitism, their alternate or at times opposite 
leaves, their progressive parasitic degradation, condensation of 
axis, and eventually non-chlorophylloid aspect. They only 
differ in the two-celled ovary, but Scrophulariaceae seem to be 
united with Orobanchaceae by Christisonia neilgherrica, with 
its two-celled, becoming above one-celled ovary, as well as by 
Lathraea with its imperfectly two-celled ovary. (3) The Oro- 
banchaceae stand by themselves as a family. 

To take the last caption first, Orobanchaceae being wholly 
parasitic and non-chlorophylloid, clearly suggests that physiolog- 
ically and now morphologically it is a degenerate offshoot from 
some family that tended gradually to show semi-parasitic habit. 
Now of all the Bilabiatae, there is only one other family which 
shows, like Orobanchaceae, parasitic habits, namely, Scrophul- 
ariaceae. No Gesneraceae are parasitic, or even show a slight 



144 Boeshore — The Morphological Continuity of 

beginning of parasitism. Such being the case, the second be- 
comes that which we are inchned to favor. But the two-celled 
ovary of Scrophulariaceae and the one-celled ovary of the Oro- 
banchaceae has been the barrier to such a connection with mor- 
phologists in the past. 

As a preliminary, therefore, to subsequent studies and inves- 
tigation it may be profitable to compare groups of parasitic and 
saprophytic plants already known to us. To start with sapro- 
phytic families first, it is well known as already shortly stated 
above, that in the Burmanniaceae the green and least degraded 
genera, such as Burmannia, have three-celled ovary with cen- 
tral placentation, while in Gymnosiphon and the most degraded 
genera like Thismia and Arachnites the ovary has become one- 
celled with deep to shallow parietal placentas. 

In the large family of the Orchidaceae as now recognized by 
systematists the most primitive subdivision Apostasieae, has 
subregular flowers, three to two stamens, and a three-celled ov- 
ary to the pistil. In the more evolved subdivision Seleniped- 
ieae, the flowers are decidedly irregular, the stamens are two in 
number, and the ovary is three-celled. Root saprophytism in 
its commencing stages is amongst these not uncommon. In the 
division Cypripedieae, the stamens are still two in number, but 
the ovary usually has become one-celled by varying stages of re- 
duction in ingrowth of the carpellary margins by graded steps 
that can well be traced. Saprophytism is a frequent feature of 
their roots. In the division Orchideae, the flowers are most 
varied and highly specialized, the stamens are now reduced to 
one functional, the ovary is one-celled with shallow parietal pla- 
centas. In this division all stages of condensing degradation 
and loss of chlorophyll can be observed, till such non-chloro- 
phylloid and greatly degraded genera like Neottia and Corall- 
orhiza are reached. Unquestionably here a continuous process 
of condensing reduction and degradation in the above more or 
less related genera is correlated with increasing saprophytism, 
all of this being associated with a gradual transition from three- 
celled ovary to one-celled ovary with deep placentas and thence 
to one-celled ovary with shallow marginal placentas. 

Again, the family Ericaceae when treated in the only appro- 
priate morphological manner that explains the evolution of the 
subdivisions satisfactorily, includes primitive shrubby plants 



Scrophulariaceae and Orobanchaceae 145 

with ample green leaves that have evolved along at least three 
main lines. One line, as beautifully traced by Dr. Henderson 
(11) in a recent paper, shows condensing and degrading simpli- 
fication through saprophytism till low herbaceous shrubs with 
few scattered leaves like Chimaphila are reached, while these 
lead to the colorless greatly degraded genera of the Monotro- 
paceae like Sarcodes and Monotropa. Still another line leads 
to the parasitic Lennoaceae, the carpels of which have probably 
increased in number by subdivision of a primitive five, that re- 
main as many celled but the ovules have become reduced to two 
or one in each cavity. A third line passes to highly evolved 
types like the Azaleas, Kalmias, and Rhododendrons with ample 
leafage, and roots that are nonsaprophytic or only slightly sa- 
prophytic and ovary that is five-celled. 

In the Gentianaceae, that frequently tend to be slightlv or 
markedly saprophytic, the ovary is still two-celled in the subdi- 
vision Exacineae. In others like Lisiantheae the ovarj,' is strict- 
ly one-celled but has deep almost adjacent placental ridges. In 
the Gentianeae the one-celled ovary has shallow ridges that 
reach a climax of shallowness in the colorless degraded sapro- 
phytes Voyria and Leiphaimos. 

In the Convolvulaceae the ovary throughout is typically two- 
celled and this is retained in species generally of the parasitic 
genus Cuscuta, but a one-celled parietal condition is present in 
Erycibe. Similarly in Rafflesiaceae, the ovary is one-celled. 

From the above it is abundantly evident that alike in sapro- 
phytic and parasitic families simplifying and degrading sapro- 
phytism and parasitism nearly always are accompanied by a 
transition from a several-celled central type of placentation to 
a one-celled parietal type. 

Accepting the foregoing as an indubitable fact, the question 
may now be asked: Can close morphological affinity be traced 
from Scrophulariaceae through types that become more or less 
parasitic and eventually degraded colorless parasites, to forms 
typical of the purely parasitic and non-chlorophylloid Orobanch- 
aceae? The demonstration of this is the main thesis of the pre- 
sent paper. As strongly favoring such a position, it may be 
noted that in such a genus as Gerardia the most gradual transition 
can be traced from tall leafy green species, like G. flava {Aureo- 
laria villosa) to G. pedicularia, thence to G. piirpurea, to G. oli- 



146 Boeshore—The Morphological Continuity of 

gophylla with few pale green leaves and branches that mainly 
carry on food elaboration, and finally to the most degraded mem- 
ber, G. aphylla, in which the leaves are small pale green scales, 
still, however, provided with a few stomata, but which are in the 
last stages of disappearance. It is of interest to note the close 
resemblance in habit, structure, etc., between the two latter types 
and such South African genera as Striga and Harveya, which 
connect again with Hyobanche. All of these, but the last in par- 
ticular, closely simulate members of the so-called Orobanchaceae. 
Further, it is important to note that in the genus Christisonia 
(Campbellia) , the ovary, while mainly one-celled with deep pla- 
cental ledges, is in most of the nine species of Christisonia two- 
celled in the lower part. And so Beck (12, p. 131) has well not- 
ed, "Ausnahmsweise kammt bei letzterer ein unteren Telle 2 
facheriger Frkn. vor; es besteht somit eine starke Annaherung 
an die Gatt. Harveya." Regarding Christisonia neilgherrica 
Worsdell (13, p. 131) says, "The ovary is bilocular in its lower 
region and unilocular above; in the latter case the placentation 
is parietal. In this plant the basal portions of the two bipart- 
ite placentas very nearly meet in the centre. In the lower, bi- 
locular part of the ovary, where the projections have become 
united to form a dividing wall, the placentation is axile, two 
placentas, bearing a large number of minute ovules, projecting 
into each cavity." 

If the above morphological and physiological lines of con- 
tinuity express a correct interpretation of the lines of evolution 
pursued, it should be possible to trace certain fairly continuous 
morphological similarities as well as degradation-differences, pro- 
ceeding in relation to the following parts. 

First, since the phenomenon is fundamentally due to increas- 
ing root parasitism, we should expect to find that the root and 
gradually thereafter the vegetative stem system should show 
condensation and swelling of the condensing axis, or, that this 
axis should become rather starved and simplified. 

Second, in such condensed axes an increasing preponderance 
in relative width and importance of phloem over xylem should 
occur until in the most condensed genera it would become a pre- 
ponderant feature. 

Third, in the above process and with the increasing parasitic 
degradation the leaves would tend by degrees to become reduc- 



Scrophulariaceae and Orohanchaceae 147 

ed in size, and in nutritive capacity, till they would become re- 
duced to relatively small colorless scales. 

Fourth, according as parasitic connection might become ac- 
centuated with herbaceous plants on one hand or with arbores- 
cent plants on the other, in corresponding degree might at least 
two lines of evolution open up; one in which entire plants para- 
sitic on short-lived herbaceous hosts would become soft and de- 
graded, while on the other hand, genera parasitic on roots of 
woody and not least arborescent types, might become in corres- 
ponding measure perennial and enlarged in the infesting region. 

Detailed comparison will now be made. 

General Morphology of the Root 

In commencing parasitism as shown and illustrated in G. flava 
(Plate XII, Fig. i) the matured perennial primary root system 
is spreading, loose, and expanded, covering a large area. From 
this expanded primary root system, secondary rootlets pass out- 
ward and downward and some of these end in parasitic suckers. 
The roots are firm, strong, fibrous, and play no small part in col- 
lecting raw material from the soil. The plant still depends large- 
ly upon crude sap obtained directly from the soil for its susten- 
ance, and could possibly live an independent existence as Kerner 
(14, p. 180) has stated for Odontites. 

In G. pedicularia the root system is more condensed and 
suckers are more abundant. 

In G. purpurea (Plate XII, Fig. 2) the secondary root system, 
though delicate, is more condensed with numerous sucker en- 
largements on a variety of plants such as Grasses, Composites, 
etc. The main root from which these side rootlets arise is con- 
densed and shortened. 

From the short condensed primary root of G. aphylla (Plate 
XII, Fig. 3) spring the secondary roots which are less spreading 
than in the previous two species, wholly indicating a more close- 
ly dependent parasitism on host roots. These are smaller than 
the roots previously mentioned, being thin and fibrous with 
abundant suckers. 

Drawings of the above were made to illustrate natural size as 
nearly as possible and to show the extent of primary and sec- 
ondary roots. 

In the transition from the above types the Scrophulariaceae 
are connected with the Orobanchaceae by the genera Lathraea, 



148 Boeshore — The Morphological Continuity of 

and Christisonia. The extent of the root system of Lathraea 
is very limited; the roots are semi-woody semi-fibrous. This 
genus, as already pointed out, is by some authors regarded as a 
member of the Scrophulariaceae, by others as a member of the 
Orobanchaceae. It offers a graded transition from pale green 
and greenish purple to purple red genera like Buchnera, Har- 
veya and Hyobanche of the Scrophulariaceae to Orohanche 
of the Orobanchaceae. Kerner (15, p. 182) has described the 
parasitism of Lathraea. He says: "The young root of the seed- 
ling grows at first at the expense of reserve material stored in the 
seed, penetrates vertically into the earth and sends out lateral 
branches, which, like the main root, follow a serpentine course 
and search in the loose damp earth for a suitable nutrient sub- 
stratum. If one of these meets with a living root belonging to 
an ash, poplar, hornbeam, hazel, or other angiospermous tree, 
it fastens on to it at once and develops suckers at the points of 
contact; these suckers are at first shaped like spherical buttons, 
but soon acquire, as their size increases, the form of discs adher- 
ent to the host's root by the flattened side and with the convex 
hemispherical side turned toward the rootlet of the parasite. 
These discoid suckers cling to the root attacked by means oi a 
viscid substance produced by the outermost layer of cells. As 
in the case of the parasites already described, a bundle of ab- 
sorption-cells grows out of the core of each sucker into the root 
of the plant serving as the host, and the tips of the absorbent 

cells reach to the wood of the root" "The 

roots, which issued originally from the seedling, and their suckers 
have long since ceased to meet the requirements in respect to 
nourishment of so greatly augmented a structure, and therefore 
additional adventitious roots are produced every year, spring- 
ing from the stem and growing towards living woody branches 
of the thickness of a linger, belonging to the root of the tree or 
shrub that serves as host. When there, they bifurcate, forming 
numerous thickish filiform arms, which lay themselves upon the 
bark of the nutrient root and weave a regular web over it. 
Sometimes two or three of these root filaments of the parasite 
coalesce, forming tendrils, and the resemblance to a lace-work 
or braid is then all the more pronounced. Suckers, such as 
have been described, are developed by these root-filaments 
laterally, and more especially on the ends of the branches." 



Scrophulariaceae and Orobanchaceae 149 

Did we know the parasitic root relations of Harveya and Hyo- 
banche, these in all probability form a more perfectly graded con- 
nection between the tvvo supposed distinct orders. 

From the above we pass to Orobanche, e. g., 0. minor 
(Plate XII, Fig. 4), in which a dense mass of secondary roots 
starts from a swollen shortened primarj^-root and these roots 
form by their surfaces intimate and close connections with the 
host roots, as described and figured by Koch (16). In 0. crii- 
enta the primary root swelling becomes more pronounced and 
the place of junction between stem and root is collar-like in ap- 
pearance. Here two lines of deviation seem to start in conden- 
sing degradation. 

One line, simplifying and short-lived, leads to Aphyllon 
(Plate XIII, Fig. 6) in which as figured by the writer there is 
even more close and extensive parasitic connection with the host 
than in the previous types and the parasite itself, in that sec- 
ondary and probably primary roots parasitize. At the base of 
the short stem arises the primary root, now slightly swollen, 
and from this are given off secondary roots in such numbers as 
to form a very much tangled mass. 

Another line leads to the larger stronger genus Epiphegiis 
(Plate XIII, Fig. 7) of annual duration, in which a tuberous 
swelling from a half inch to an inch across represents a fused pri- 
mary root below and a greatly condensed vegetative stem-axis 
above. From the lower part or primary root short and now 
functionless rootlets start, while from the condensed stem adven- 
titious roots, similar in relation to the secondary ones, arise at 
any point of the stem axis. Accordingly parasitic connection 
with the host is easily and directly made by the germinating 
primary root as already pointed out by Cooke and Schively (17). 
The roots of Epiphegiis form around and above the beech roots 
on which this is parasitic. The secondary and adventitious 
roots are short and delicate. 

In Conopholis (Plate XVI, Fig. 33), which may be regarded 
as the climax type of the group, the root system so far as known 
is entirely hidden from external view, being represented by a 
large swelling and which usually terminates the oak root on 
which it grows. Alike roots and leaves have been entirely ab- 
sorbed, although in Epiphegiis rudiments of both are present. 
From the swelling arise numerous flowering shoots. 



I50 Boeshore — The Morphological Continuity of 

Further comparison of the last three genera will show that 
the parasitic roots of Aphyllon do not cause truncation and de- 
cay of the host roots, the latter remaining alive beyond the point 
of attack, while in Epiphegiis and Conopholis so complete is 
the parasitism that host roots rarely remain alive beyond the 
point of parasitic attachment. In almost all of the genera of 
the Orobanchaceae parasitism has become highly specialized 
with regard to selection of hosts. 

Thus a continuous and easy gradation is traced from green 
and nearly independent Scrophulariaceae to highly condensed 
and degraded Orobanchaceae, which in Conopholis closely simu- 
lates the most degraded representatives of the Balanophoraceae 
and Rafflesiaceae. On the other hand, no even approximate or 
suggested such connection is shown between Gesneraceae and 
Orobanchaceae. 

Histology of the Root 

In all the species of Gerardia examined the internal structure 
of the roots is of the radial polyarch type. The xylem is great- 
ly in excess of the phloem and consists in young roots, like those 
of G. purpurea, mainly of large pitted vessels; spiral tracheae 
and xylem cells make up the rest of the xylem. The phloem 
arms alternate with the xylem and are composed of the usual 
elements. In older roots of G. purpurea, G. flava, G. aphylla, 
the bundle system assumes a woody more dense character, 
having the appearance of a ring of wood not unlike that seen in 
a dicotyledonous stem, save for the presence of the phloem. A 
considerable amount of hard bast develops. A several-layered 
pericambium surrounds the bundle region and this in turn is 
surrounded by an endodermal layer, easily recognized in young 
roots. The cortex is variously developed: in small, young roots 
it consists of cells in rows, of 2 to 3 cells in each, and these are 
radially disposed and connect the epidermis with the other tis- 
sues, while between these radial arms are very large open spaces; 
in older roots the cortical space is filled with normal thin-walled 
cells; in more mature roots of G. flava the cortex is composed 
almost wholly of scleroid cells staining a deep red color in saf- 
ranin. In mature roots the epidermis may be replaced by cork 
tissue. Root hairs were also noted. 

In the parasitism of Gerardia the roots produce swellings in 
the regions of contact with the host, which become hemispher- 



Scrophulariaceae and Orohanchaceae 151 

ical and grow down the sides of the host roots but do not com- 
pletely surround them. Sections of swellings show an epi- 
dermis, a cortex, and bundle elements. The most conspicuous 
feature of the bundles is the large number of cells with pitted 
walls. The cells in the upper part of the swelling have not fused 
to any great extent to form vessels, but in the lower spread-out 
part of the swelling they have the appearance of vessels (with 
pitted-reticulate thickenings in their walls) which establish a 
connection with the xylem of the host roots. This was seen in 
purpurea and pedicularia. 

Roots of Harveya and Hyobanche were not available for inves- 
tigation. 

Transverse sections of the roots of Lathraea japonica show 
the epidermis, a narrow cortex, and the polyarch bundle system. 
In the latter unusually large pitted vessels make up the greater 
part of the bundles. 

The roots of Aphyllon are soft and delicate, drying quickly 
when exposed to the air. They never completely surround the 
host roots, nor do they develop as large swellings as seen in Ger- 
ardia species when contact is made with the host. The orig- 
inal root tissues seem to fuse more intimately with the corres- 
ponding tissues of the host. Root hairs and root caps, as already 
noted by Smith (18, p. 113), were not found. 

The radial arch-system is maintained, but the bundles are few 
in number; the small amount of xylem consisting of spiral tra- 
cheae and pitted vessels is poorly developed. The amount of 
phloem greatly exceeds that of the xylem, which is a feature we 
should expect to find in a holoparasitic plant whose chief object 
of parasitism is elaborated sap. The bundle system is surround- 
ed by a pericambium and this in turn by a wide cortex of very 
large cells with abundant quantities of starch. No stone cells 
have been found in it. Surrounding the cortex is the epidermal 
layer. So intimate and complete is the connection made with 
the host roots that, epidermis of parasite is continuous with epi- 
dermis of host, cortex of parasite with cortex of host, etc., and 
were it not for the large cells of cortex with abundant contents 
as compared with the same tissue of the host, the line of demar- 
cation between the two could scarcely be distinguished. In all 
this Aphyllon closely simulates species of Orohanche as figured 
by Koch (19). 



152 Boeshore — The Morphological Continuity of 

As a still more condensed type Christisonia might well come 
next to Aphyllon. This is described and figured by Worsdell 
(20, p. 134). He describes three species of Christisonia, but 
the one that concerns us here is Christisonia subacaulis. To 
quote from him regarding it: "the most abnormal feature oc- 
curring in these plants is presented by the subterranean portion 
of Christisonia suhacaulis especially, which, on investigation, 
is discovered to consist of organs having the character of roots, 
though their morphological nature is well concealed, owing to 
their extreme modification arising from their parasitic habit 
. . . The tubers, which arise at intervals in the root system 
of the plant just named, are the most important parts of it, for 
it is from these that the haustoria are chiefly formed, while they 
also act as reservoirs of nutriment for the whole plant . . . 
The haustorium is interesting as having an exogenous origin, 
and not an endogenous one, as described for many other para- 
sites; it agrees in this respect with that of Rhinanthus." 

The roots of Epiphegus are shorter than the roots of Aphyllon 
and seem to have lost all parasitic power, this function being 
accomplished by the tuberous swelling. A transverse section 
of such shows the host root deeply or shallowly buried within 
the tissues of the tuber and thus connection is established be- 
tween the two. In these degradation stages the tissues of the 
parasite have become correspondingly more simplified as demon- 
strated by Cooke and Schively (17). 

In Conopholis (Plate XVI, Fig. 32) no external roots are visi- 
ble. With the more complete and highly specialized paras- 
itism has come a complete absorption of roots, or they may be 
represented by a large mass of stone cells, but wholly buried 
within the enormous swelling on the oak roots. One specimen 
was found which measured 10 inches in length and 6 inches 
across. Sections were made of smaller specimens but these 
only showed masses of stone cells. All trace of definite systems 
seem to have been lost. And so, Conopholis well represents, 
both morphologically and physiologically, the climax of the en- 
tire group. 

In summing up the discussion on roots it can be said that, be- 
ginning with G. flava and ending with the genus Lathraea, a 
gradual condensation in extent of root system is accompanied 
by a gradual degradation of root tissues which in Lathraea be- 



Scrophulariaceae and Orohanchaceae 153 

come semi-woody, semi-fibrous. With this degradation par- 
asitism becomes of increasing importance. Further conden- 
sation leads to Orohanche and Aphyllon with soft delicate roots 
and such is accompanied by further simplification in root tis- 
sues. From here the root system enlarges, becomes tuberous, 
and is characterized by an increasing degree of hardness of the 
tissues that reaches a climax in Conopholis. Further simplifi- 
cation of tissues here results in unintelligible interpretation. 

Comparative Morphology and Physiology of Stem and 

Leaf 

Under this heading stems and leaves will be considered. The 
drawings accompanying this part of the paper were made to il- 
lustrate more particularly relative lengths of stems. 

In the most primitive Gerardias the stem is tall, well formed, 
and typically normal dicotyledonous, attaining a height of i to 
4 feet in G. flava (Plate XIV, Fig. 9). The lower leaves are 
large, ovate-lanceolate, sinuate-toothed along the margins; in the 
upper leaves the margins are entire. Both stem and leaves are 
covered with a fine close down. 

Transverse sections of the stem show a large pith area, a ring 
of x>dem with numerous pitted vessels and internal to these spir- 
al tracheae, a cambium, a narrow zone of phloem consisting of 
little soft and much hard bast. Externally the phloem is bound- 
ed by a cortex zone of i to 5 layers of cells, with the outer region 
collenchymatous and the inner region of thin-walled cells. The 
epidermis is persistent around the stem and from it project the 
numerous two to four-celled pointed hairs. The basal cell of 
these is large, rounded; the outer cells are narrow with the tip 
cell pointed. 

G. purpurea, with stems i to 3 feet tall, has a comparatively 
small pith, but a wide zone of xylem. The phloem consists 
mainly of soft bast with occasional patches of hard bast. Scler- 
enchyma cells are a frequent feature of the cortex. The leaves 
of this species are much reduced in size, linear, acute, rough- 
margined according to Gray (21, p. 731). The rough character 
is due to many one-celled, pointed, more or less spiny hairs distri- 
buted over the general leaf surface and especially along the leaf 
margins. 



154 Boeshore — The Morphological Continuity of 

In G. aphylla (Plate XIV, Fig. lo) a very marked condensa- 
tion occurs. The stem is slender, rather wiry, unbranched, 
and from 6 to i8 inches in length. The leaves, much reduced in 
size, are scale-like, tapering almost to a point, and closely ap- 
plied to the stem. Stomata are distributed over the leaf surface 
in comparatively small numbers when the entire foliage of the 
plant is taken into account. Leaves and stem are covered with 
short, conical, unicellular hairs. 

Transverse sections of the stem taken at the same level as 
in the preceding genera are smaller in circumference. Stems 
tend to become quadrangular, being reinforced by scleroid cells 
at the angles. A rather wide green cortex surrounds the bundle 
system. Phloem consists of about equal amounts of hard and 
soft bast. Xylem is well developed and wide, enclosing a small 
pith area. 

G. aspera (Plate XIV, Fig. ii) shows further reduction in 
height of stem. The internal structure is very similar to that of 
G. aphylla. Stem and leaves have hairs similar to those of G. 
purpurea. 

Condensation advances even more markedly in Harveya and 
Hyohanche (Plate XIV, Fig. 12, 13) in that the stem is only from 
4 to 6 inches in height. Both genera are parasitic, have scale-like 
leaves or these even reduced to functionless scales. Wettstein 
(22,p.97) describes Hyobanche as a fleshy low, parasitic plant with 
numerous scale-formed leaves, the lower scales being smaller 
than the upper ones. Material of this genus was not available 
for study, but the foregoing description regarding the fleshy na- 
ture of the plant suggests a very strong tendency toward genera 
of Orobanchaceae. 

Transverse sections of the stem of H. coccinea have a wide 
pith around which the ring of bundles is arranged. These are 
more simplified than in the preceding genera, and in this respect 
Harveya is a good transition from species of Gerardia to Oroban- 
che of the Orobanchaceae, in fact it is closer to Orobanche than to 
Gerardia. The xylem, while forming a continuous ring, is nar- 
row in places and irregular; its elements are spiral tracheae and 
pitted vessels. The phloem is in excess of the xylem, soft bast 
of I to 3 layers of cells in patches, and hard bast that is very strik- 
ingly developed as 3 to 6 layers of cells forming a solid ring about 
the soft bast. The cortex is as wide as the phloem and xylem 



Scrophulariaceae and Orohanchaceae 155 

combined and in places attains twice their extent in width; the 
cell walls show irregularity. The epidermis, from herbarium 
material, could not be described very accurately. 

The hairs of H. coccinea are of special interest because of 
their large number, great size, and capitate-glandular character. 
They are distributed over both stem and scales; as many as 20 
were counted around the edge of a cross section of the stem of 
reasonable thickness, which does not account for any that were 
broken off. The "stalk" of each hair consists of from 3 to 5 
cells; the basal cell is usually short, broad, and rounded, while 
the others are elongated almost cylindrical; where two cells join, 
there is a collar-like constriction, giving the "stalk" the appear- 
ance of being jointed. The glandular tip is composed of 2 to 4 
cells. Here again this genus is very similar to Orobanche which 
will be described later. 

Proceeding from the last mentioned genus through the genera 
of Orobanchaceae the vegetative axes become more or less in- 
conspicuous though enlarged fleshy (in some genera) and tuber- 
ous, and partly or wholly subterranean. 

In the transition genus Lathraea (Plate XIII, Fig. 14) the 
vegetative axis has become a rhizome from 2 to 4 or 6 inches 
long, and is provided with the hollow scale leaves concerning 
which so much discussion has taken place, while from the an- 
nual short-lived inflorescence numerous flowers arise. The 
plant is described by Kerner (23, p. 135) as being destitute of 
chlorophyll. "The subterranean stems are white, have a fleshy, 
solid, and elastic appearance, and are covered throughout their 
entire length with thick squamous leaves placed closely one 
above the other. " The leaves are broadly cordate. The scales 
being underground, naturally have lost their vegetative func- 
tion, but are provided with cavities and structures for catching 
animal prey. Solereder (24, p. 586) says that the function as- 
cribed by Kerner and Wettstein to these structures is incorrect 
according to Scherffel and Heinricher. Kerner describes two 
kinds of structures formed on the internal surfaces of the scale 
for which he suggests no special name in Lathraea squamaria; 
others have called them glands. One kind is composed of a cy- 
lindrical stalk cell and two cells forming a head, which project 
into the cavity of the scale; the other variety, which does not 
project into the scale, is composed of a tabular cell and two con- 



156 Boeshore — The MorpJwlogical Continuity of 

vex cells, forming a low dome amongst the epidermal cells. The 
writer examined scales of L japonica and found similar struc- 
tures projecting into the cavities of the scale. The cells of the 
epidermal tissues are from 4- to 6-sided and regular in outline. 
Stoma ta are either absent or present in small numbers; struc- 
tures were found that had much the appearance of stomata, but 
no accurate statement regarding them could be made. 

In the genus Orobanche (Plate XIII, Fig. 15) the vegetative 
axis is an inch and a half or less in length. If the rhizome of 
Lathraea be thought of as shortened and as a consequence the 
axis became tuberous and enlarged, the condition of affairs in 
Orobanche would be reached in which the stem axis is a short- 
ened but enlarged tuber, covered densely with crowded scales. 
These are more elongated than the scales of Lathraea, e. g., 
in 0. minor, broad oval at the base and lanceolate in their upper 
part; along the flowering axis they are lanceolate. 

In 0. cruetita the stem is exceptionally broad, measuring three- 
fourths of an inch across. 

In transverse sections of the stem of 0. minor their outline 
is found to be very irregular, which is due to some extent to the 
scales given off at different levels. There is however, irregular- 
ity also due to grooves and rather wide ridges, which become 
greater in number and more pronounced on the floral axis. 
Such sections show sections of the scales, as well, from whose 
outer surface are given off the glandular hairs, which agree in 
description with the hairs of Harvey a. From 3 to 5 cells form 
a stalk with the capitate part of the hair of 2 to 4 cells. The 
cortex is unmodified, consisting of large thin-walled cells which 
are packed with starch grains. The bundle system consists of 
bundles arranged in an irregular manner about the pith area; 
phloem is next to the cortex and xylem next to the pith. The 
pith area is large and like the cortex has considerable starch in 
its cells. 

Transverse sections of the flowering axis of 0. coeridea show 
the irregularity in outline mentioned above to the greatest de- 
gree. The epidermal cells have heavy outer walls. The hairs 
are of the same type as for Harveya and 0. minor, and are 
quite numerous. The cortex cells are thin-walled and have less 
starch than those of the stem cortex. The bundle system tends 
to become more loose and open than in the previous genera and 



Scrophulariaceae and Orohanchaceae 157 

in places the bundles are separated; the amount of phloem is 
about twice that of the xylem and consists of hard and soft bast; 
the xylem has a few spiral tracheae and pitted vessels, that we 
best see in longitudinal sections. 

The vegetative axis of Aphyllon (Plate XIII, Fig. 16) is 
reduced in thickness to scarcely more than one-fourth of an inch, 
or usually less, but in length is about one inch. The number of 
scale leaves is reduced to from 5 to 10, alternately placed and 
separated on the stem; they are smaller than the scales of Oro- 
banche and decrease in size from the upper to the lower ones. 
The lower ones have neither stomata nor hairs, while the upper 
ones have both. The hairs are capitate and multicellular, like 
those of Harvey a and Orobanche. 

In making cross sections of the stem their soft and fleshy nat- 
ure is at once recognized. The epidermis consists of small cells 
which are thickened on the free side; amongst these, stomata 
may be seen. The most conspicuous feature of the stem is the 
unusually large rounded thin-walled cells in the cortex and pith. 
Both regions are wide in extent and their cells are packed with 
large starch grains. Between these regions a comparatively 
narrow ring of bundles is arranged. The bundles are more wide- 
ly separated than in Orobanche, thus making the medullary 
rays quite wide. Around the bundle system is a sheath of from 
2 to 4 layers of cells, much smaller than the cortex cells and 
whose greater diameter is placed in a tangential direction. The 
excess amount of phloem over xylem is more pronounced than 
in the previous two genera. The phloem is external and xylem 
internal, the latter composed of a few spiral tracheae and pitted- 
reticulate cells. 

Transverse sections of the flower stalk show the same arrange- 
ment of tissues as in the stem. The bundles are placed in a nar- 
row ring about the pith and internal to the cortex; the xylem is 
slightly better developed than in the stem, while the phloem 
forms a continuous zone about the xylem. Cortex and pith 
have some starch grains. The epidermis, of small cells with 
free walls heavily thickened, is frequently interrupted by cells 
in groups of two slightly raised above its surface which appear 
to be stomata. Glandular capitate hairs, arising in great num- 
ber from the flower stalk, have also two cells forming their base. 

In Epiphegus (Plate XIII, Fig. 7) the vegetative stem and 
enlarged primary root tubercle become confluent into an oval 



158 Boeshore — The Morphological Continuity 0) 

or rounded tuber from three-fourths to an inch and a half long. 
The writer considers the upper part of the tuber as the stem axis 
which bears the tooth-like scale-leaves. In some specimens the 
stem part consists of more than half of the tuber, in others of 
less than half. The scales are shorter, but more numerous than 
those of Aphyllon. Stomata are present on the scales, and 
along the scale-edge a few multicellular hairs were seen. Ad- 
ventitious roots arise from the surface of the stem. 

Histological details have been worked out by Cooke and 
Schively and the writer has found his own investigations to agree 
with their descriptions. But by way of comparison of this genus 
with preceding genera some of these details will bear repetition. 
The most notable feature is the bundle system, which becomes 
broken up into separate bundles that have no definite arrange- 
ment in rings, thus giving the stem a more loose and open as- 
pect. This is an advance in degradation from Aphyllon in 
which the bundles, though separated, form a fairly definite ring 
about the pith. The phloem greatly exceeds the xylem, a fur- 
ther advance in degradation with increased parasitic habit. To 
quote shortly from Cooke and Schively: "The phloem of a 
bundle .... shows a tendency to spread out and lie in 
separate patches, while the xylem of each bundle seems always 
concentrated in a single area. Many of the bundles show an in- 
ternal duplication with reversed order, phloem, xylem, xylem, 
phloem, succeeding each other from without inwards . . . 
An internal phloem is almost always present, often in excess of 
the outer phloem mass." No such state of affairs as the last 
exists in Aphyllon. As a consequence of the scattered and 
elongated bundles the cortex and pith areas have become re- 
duced in size. 

Sections of the floral axis have been described by others. The 
bundles are arranged in a ring. Considerable hard bast is de- 
veloped. Hairs and stomata constitute the epidermal growths, 
the former showing considerable reduction in size as compared 
with the hairs on the floral axis of Aphyllon. 

No definite statement will be ventured as to how much of the 
plant constitutes the stem axis in Conopholis (Plate XVI, Fig. 
32). The aerial portion in its lower part is densely covered with 
scales that may represent reduced and degraded leaves, while 
slightly above this point the scales become more distinct, sep- 



Scrophulariaceae and Orobanchaceae 159 

arated from one another, and increased in size, averaging 4 to 
6 times the size of the lower ones. Sections made in the region 
of the crowded small scales show numerous patches of hard 
scleroid cells and the inner almost continuous ring of bundles, 
while in the position of the outer ring some fairly recognizable 
bundles are seen. Above this point the two rings of bundles 
become complete and the scleroid patches disappear; below this 
point the bundles become fewer in number and less recogniz- 
able, but the scleroid patches increase in number until in the 
tuberous part scleroid patches are the predominant feature and 
the bundles as such disappear. Evidently the lower part of the 
aerial portion represents a transition from stem axis to aerial 
shoot, and so, this part together with the upper part of the tub- 
erous swelling might be considered as the stem axis. As in 
Epiphegus, stem system and root system have become con- 
fluent with no sharp line of distinction between the two. 

Stomata have been reported absent from the scales but sev- 
eral were found on the lower or outer surface of the upper scales. 
From their shape they appear to be almost or quite function- 
less (Plate XV, Fig. 28). They are misshapen and poorly de- 
veloped; some have two elongated guard cells which have 
slipped out of position and show a long orifice between them, 
others have three and four guard cells very loosely fitted to- 
gether. Large multicellular and unicellular hairs are found on 
the edges of the scales which the drawings (Plate XV, Fig. 31) 
will sufficiently indicate. 

The histology of the flowering axis is interesting for several 
reasons. The cortex and pith areas are quite large and consist 
of rounded cells of varying size and thickness with frequent 
large intercellular spaces. Some of the cells have contents while 
others are empty. Two definite rings of bundles surround the 
pith, which have a zone of fundamental tissue intervening. 
This quite agrees with Wilson's observations (25, p. 14) but dis- 
agrees with those of Chatin (26, p. 590) who says that Epiphegus 
and Conopholis have three rings. The majority of bundles 
in both rings are completely separated from each other by fun- 
damental tissue, and this represents the climax in the series, 
beginning with Harveya in which the bundle system shows no 
tendency toward separation of bundles, thence to Orohanche 
which shows indications of such, thence to AphyUon in which 



i6o Boeshore — The Morphological Continuity oj 

the bundles show sHght separation, thence to Epiphegus in 
which the bundle system is loose and broken up into separate 
bundles, which finally in Conopholis become still more widely 
separated and distinct. 

As to the elements making up the bundles, the following is 
stated by Wilson (25): "Each bundle of the inner row has in- 
ternally xylem, made of xylem cells and well-developed spiral 
tracheae. Next to the xylem is found the phloem, which in a 
longitudinal section proves to consist of both sieve tubes and 
companion cells. Adjacent to the phloem are a number of par- 
enchyma cells, whose walls are so angular and so much thick- 
ened that in the photograph these bundles appear to be bi-col- 
lateral. That such is not the case, however, is easily proved on 
longitudinal section, when the parenchymatous nature of these 
cells is at once visible. Even in cross section, the color of the 
walls differentiates the wood from the thickened parenchyma. 

The bundles of the exterior row have the same structure as 
those of the interior, only the xylem is now exterior so that the 
phloem masses of the two rows face each other." 

Sections stained in safranin and methyl green also some in 
Delafield's haematoxylin and safranin bring out the bundle ele- 
ments quite plainly. A different interpretation from the above, 
however, is suggested with reference to the arrangement of the 
elements of the bundle. Each bundle of the inner ring shows 
internally phloem, consisting of a large patch of hard bast and 
a patch of soft bast. The xylem comes next and is poorly de- 
veloped, consisting of an interrupted line of cells, which are al- 
most wholly large spiral tracheae, running across the bundle; 
in some bundles there are several rows of spiral tracheae and 
amongst them are several cells of phloem. Beyond the xylem 
is another small patch of soft bast and next to it another small 
patch of hard bast. The bundles of the outer ring show the 
same elements, but in reverse order, small patches of hard and 
soft bast, xylem, large patches of soft and hard bast. 

Comparative Study of the Inflorescence 

Regarding the inflorescence of the two supposed distinct fam- 
ilies, several points are of special interest. In the parasitic 
Scrophulariaceae the flowering axes are elevated above the sur- 
face of the soil by the more or less elongated vegetative axes in 



Scrophulariaceae and Orobanchaceae i6l 

the less parasitic forms, but as these intervening vegetative axes 
become shortened and increasingly degraded in the more par- 
asitic forms hke Harveya and Hyobanche the flowering stalks 
gradually approach a lower level until they take their origin 
only a few inches from the ground. The conspicuous part of 
the plant then consists of the short vegetative axis and the floral 
axis. In the Orobanchaceae with the greatly reduced stems the 
flowering axes constitute almost wholly the aerial parts of the 
plant. In the former the flowering axes are woody, while in 
the latter they are more or less fleshy and stout, with one excep- 
tion (Aphyllon). 

The type of inflorescence for the Scrophulariaceae is given 
by systematists as centripetal, racemose. Gerardia flava has 
one floral axis along which short-pedicelled flowers are arranged 
racemosely. In G. purpurea, G. aspera, G. aphylla and 
others there are several floral axes, each of which constitutes a 
raceme; the pedicels are of varying lengths. In some of the 
more parasitic forms the branching of the flower stalk is less fre- 
quent and the flowers have very short pedicels so that the type 
of inflorescence tends to become a loose spike, e. g. Orthocarpus 
purpurea, Euphrasia, Bartsia viscosa, Odontites, Hyobanche, etc. 

Aphyllon has one floral axis bearing a terminal flower. Epip- 
hegus has branched flowering stalks and the flowers are ar- 
ranged racemosely or in a spike. In the other genera, Lath- 
raea, Orobanche, and Conopholis, of the Orobanchaceae the 
flowers are arranged in a dense spike. 

The bracts of the flowers in Scrophulariaceae are leaf-like 
becoming scale-like, or even scales in Hyobanche while in Oro- 
banchaceae they are scales. 

Comparative Study of the Flower 
Calyx. 

The calyx in the different genera studied shows considerable 
variation in the number of sepals, in form, and in hairs. 

In species of Pedicularis the calyx may be in the form of a 
funnel, or bell-shaped with from 2 to 5 teeth at the top. The 
teeth may be simple or further toothed or lobed. 

The calyx of Melampyrum lineare is comparatively small and 
is made up of a short tube below and 4 tapering teeth above, the 



i62 Boeshore — The Morphological Continuity of 

teeth being longer than the tube. These are in pairs, with the 
upper pair sHghtly longer than the lower pair. Short, blunt, 
unicellular hairs and stomata are distributed over the surface 
of the calyx. 

In Bellardia the calyx is much larger than in Melampyrum, 
and consists of the lower half of a bell-shape while the upper 
half is divided into 4 teeth. As in Melampyrum, the two lower 
teeth are about two-thirds the size of the upper ones. A prom- 
inent vein runs into each tooth. The hairs are numerous and of 
two kinds; very long, slender, unicellular, pointed hairs are 
found mainly along the edges of the teeth and prominent veins, 
and the less numerous 3- to 4-celled glandular hairs only along 
the main veins and edges of the teeth ; while between the prom- 
inent veins they are almost wholly of the pointed type, but short 
and unicellular. Stomata are also present. 

In Fistidaria (Alectorolophus Bieb., Rhinanthus L. p. p.) the 
calyx consists of 4 sepals in pairs, the parts of which are united 
almost to their tips, but the pairs are separated for more than 
half of their length. Two sides of the calyx are pressed together 
in the young state, which in the fruiting stage become inflated 
and persistent around the fruit. Two types of hair are found 
on the surface; a short unicellular, and a long multicellular 
pointed type, also a glandular type with two rounded cells form- 
ing the top. 

In species of Gerardia the bell-shaped calyx is 5-toothed, the 
teeth in most cases are shorter than the tube. In G. purpurea the 
teeth are very short to half the length of the tube and sharp- 
pointed. G. flava was referred to before as covered with a fine 
close down, which character applies to the calyx as well. A 
peculiar feature of the hairs in this species is the spiral thicken- 
ings found in them. The short pointed type is rare or wanting 
entirely. In G. aspera and G. purpurea the short, pointed hairs 
are the predominant type; these are both one- and several-celled. 
The latter has also short glandular hairs. Stomata are a com- 
mon feature in the three species. The epidermal cells are reg- 
ular in outline. 

In Euphrasia americana the calyx is small, 4-toothed, the 
teeth being longer than the tube and lanceolate. Pointed uni- 
cellular hairs are quite common, but are not found all the way to 
the tip of the calyx teeth. The short glandular hairs are con- 



Scrophulariaceae and Orobanchaceae 163 

fined largely to the angles formed by the bases of the calyx teeth. 
The former type is roughened along the margins. Epider- 
mal cell walls are wavy. 

Bartsia alpina has a relatively large calyx of 4 parts, with the 
teeth about as long as the tubular part. Long-stalked gland- 
ular hairs are abundant; the stalk consists of 3 to 6 slender cells, 
while the top of it has from 2 to 5 cells arranged in parallel rows. 
Pointed multicellular hairs, though present, are few in number. 
Epidermal cells are irregular in outline. 

In Harveya the tubular part of the calyx is short and the 5 
lobes extend almost to the base. As already described in con- 
nection with the stem histology, the hairs are of maximum size 
and wholly glandular. The stalk cells are comparatively wide 
and stout, are 3 to 6 in number, and capped by the gland cells. 
Unlike the majority of the genera already described, the hairs 
in this genus fringe the edges of the sepals. 

Hyobanche has a calyy of 5 parts which are almost distinct 
and more rounded than in Harveya. 

Among the Orobanchaceae similar variation may be seen in 
the calyx, as in Scrophulariaceae. According to Le Maout and 
Decaisne (27, p. 593) the "calyx is persistent, tubular or cam- 
panulate, 4-5 fid, or of 4 sepals more or less completely united in 
lateral pairs." 

In species of Orobanche variation occurs, for the calyx may be 
split both above and below, nearly or quite to the base; the di- 
visions may be 2-cleft or entire, or more or less unequally 2- to 
5-toothed. In 0. coerulea and 0. minor the teeth are about as 
long as the tube, and are lanceolate-subulate. The hairs on 
these two species are similar to those of Harveya but smaller. 

The calyx of Epiphegus is small, the teeth very much shorter 
than the tube below. Cooke and Schively (28, o. 377) state 
the following concerning hairs: "One-celled, rarely two-celled 
hairs fringe the edges of the lobes. Below, across the base of 
the lobes, there extends a band of two or three-celled hairs, 
longer than the uoper hairs. All of these hairs are on the outer 
surface of the calyx ; none are present on the inner surface. They 
have a swollen granular appearance." The writer has found 
his own descriptions to agree with the above. 

In Lathraea the calyx is bell-shaped with 4 to 5 rounded teelli 
above. 



164 • Boeshore — The Murphological Co7itmuity of 

The calyx of Aphyllon is 5-toothed, the teeth equal to, or 
longer than the tube. Glandular hairs are numerous and dis- 
tributed over the entire outer surface of the calyx; shortly, these 
consist of a short broad basal cell, then a long cylindric cell, 
next to this 2 to 3 cells decreasing in size, and finally the top or 
capitate part of several rounded cells. Stomata are numerous 
and of the normal type. 

In Conopholis the calyx is orbicular, split in front, and toothed 
at the tip. Hairs and stomata are negligible in this genus. 

Stamens. 

The stamens in parasitic Scrophulariaceae and Orobanchaceae 
are 4, didynamous, in Gesneraceae, 5 to 4 to 2. 

As to anthers, a totally different relation holds between par- 
asitic Scrophulariaceae and Orobanchaceae on the one hand as 
compared with Gesneraceae on the other. In the former the 
top of the filament is broadly inserted into the swollen back of 
the anther, the lobes of which in the parasitic Scrophulariaceae 
and Orobanchaceae are prolonged above the connections, but 
in a striking manner are prolonged downward as two parallel 
or divergent aw^ns. These anther lobes in all except two gen- 
era of Scrophulariaceae {Harveya, Hyobanche) and two genera 
of Orobanchaceae (Campbellia, Aeginetia) are like each other, 
that is, are equally paired anther lobes. But in Ilarveya one 
anther lobe is large, normal, and poUeniferous, and prolonged 
below into a long horn; the other lobe is small, abortive, and 
radiates back from the top of the filament. The latter anther 
lobe in Hyobanche has been entirely absorbed, so that now one 
fertile anther lobe dehisces by a single basilar pore. 

It is of interest to find that in Christisonia and Aeginetia of 
the Orobanchaceae a similar structure exists, for, as in Hyo- 
banche and Harveya, each bears a single fertile anther lobe. 

As to antherine structure, this exactly agrees in parasitic 
Scrophulariaceae and Orobanchaceae and totally differs from 
anything encountered in Gesneraceae. The structure and ap- 
pearance of such genera as Melampyrum, Tozzia, Euphrasia, 
PediculariSy Buchnera, Gerardia, Bartsia, etc., absolutely resemble 
those of Orobanchaceae, and this the writer would regard as 
one of the most important points of contact between the two 
families. 



Scrophidariaceae and Orobanchaceae 165 

The anthers in the various genera of the Gesneraceae con- 
form to a totally different type from that shown ahke in Scro- 
phulariaceae and Orobanchaceae. In the former, when the 
flowers become nearly or quite regular as in cultivated varieties 
of Gloxinia and also in species of Streptocarpus, as well as in other 
genera, the anther lobes are adpressed at their tips and cohere 
so as to form a solid antherine box. When the flowers are ir- 
regular, as in nearly all members of the family, the 4 anthers are 
pressed together in pairs by their tips. In the entire group fur- 
ther, the bases of the anthers are either parallel and with blunt 
rounded extremities, or the anther lobes diverge in their lower 
part but are blunt and rounded in their divaricate bases. In 
no case studied by the writer is there any indication of the anther 
lobes being arranged in parallel pairs that at their lower ex- 
tremities become prolonged into horned or horn-like awns. 
This peculiarity is typical, as will be traced, in most of the 
known parasitic Scrophulariaceae and directly continued as a 
character to the Orobanchaceae. 

Of all the genera examined Gerardia flava might well be placed 
at the top of the list regarding the size of its anthers. As illus- 
trated in Plate XV, Fig. 17, the anther lobes are large, ellip- 
tical, rounded at the upper extremities and at their lower ex- 
tremities are projected abruptly into two long tapered, some- 
what divergent processes. The front and sides of the anthers 
are covered with numerous long, multicellular hairs. These 
are present also on the filaments. 

The anthers of G. purpurea (Plate XV, Fig. 18) are smaller and 
taper more gradually downward into processes that lie almost 
parallel with each other. The filament is inserted above the 
middle of the anther lobes. Anthers and filaments are hairy. 

In G. aphylla (Plate XV, Fig. 24) and G. aspera the processes 
are relatively short and less pointed than in the former species. 
Both anthers and filaments are covered with hairs. 

In Melampyrum lineare the anthers agree fairly well with those 
of G. purpurea, but are smaller. Along the filaments knob-like 
swellings of i to 2 cells are seen. 

The antherine condition of Harveya is set forth in Plate XV, 
Fig. 19 and has already been referred to. 

Other genera of Scrophulariaceae like Bartsia (Plate XV, Fig. 
20) Tozzia, Bellardia, show likewise the downwardly-direc- 
ted anther-processes. 



1 66 Boeshore — The Morphological Continuity of 

For Lathraea squamaria Kerner figures basal anther-processes 
similar to those in the above genera. 

The stamens of two species of Orobanche, also those of Aphyl- 
lon, Epiphegus and Conopholis are figured in Plate XV, Figs. 
25, 26, 27, 23, 22, all of which have the downwardly-directed 
processes. 

In Orobanche coeriilea the anther lobes are round above and 
taper gradually downward into rather short processes at their 
lower extremities, which are slightly convergent. 

In 0. minor the shape of the anther lobes is approximately 
rectangular, with the processes given off from the sides next to 
the filament. 

In Aphyllon the anthers are comparatively small. The fila- 
ment is inserted above the middle of the anther lobes, with the 
processes at their lower extremities. 

Hairs on the stamens are a constant feature in all the above. 

The parasitic Scrophulariaceae and Orobanchaceae thus have 
a character in common. Further, this character becomes more 
important when the function of the processes is considered, for 
in both groups these are contrivances designed to aid in the shed- 
ding and dissemination of the pollen grains. With regard to 
the genus Bartsia, Knuth (29, p. 229) says of B. apula the fol- 
lowing: "In this Dalmatian species each anther possesses a 
downwardly-pointing process, which is pushed to one side by 
insects, thus opening the pollen receptacle and causing pollen 
to be sprinkled on the head and back of the visitor." 

In connection with the description of pollination in Lathraea 
squamaria the statement is made by Knuth that the pollen can 
not fall out until the short, blunt point of an anther receives a 
blow from an insect. Again, under species of Orobanche the 
following is stated: "The four anthers are laterally united, and 
each lobe is provided with a sharp, stiff, downwardly-directed 
process. These processes are behind the stigma, and if any- 
thing strikes against them the bright-yellow, powdery pollen 
falls out of the anther-lobes, and is sprinkled on the proboscis 
or head of the visitor." 

Histologically the structure of the awns shows a striking 
agreement throughout the genera of Scrophulariaceae and Oro- 
banchaceae already mentioned, in that as one passes from each 
anther lobe toward their down vvardly-direc ted awns the epider- 



Scrophulariaceae and Orobanchaceae 167 

mis or exothecial tissues become increasingly thickened on their 
outer and lateral walls in u-shaped manner until toward the tip 
of each awn the thickening may be almost as deep as the cell 
cavity. Transverse and longitudinal sections of the awns of 
Aphyllon are figured in Plate XV, Figs. 29, 30. 

Were the above not a continuous morphological series from 
green to degraded parasitic plants, one can scarcely suppose 
that such similarities and histological details could have evolved 
in two such related families. 

Pistil 

In a study of the pistil the fundamental point for consider- 
ation is the supposed invariable two-celled ovary in Scrophulari- 
aceae and the one-celled ovary in Orobanchaceae and Gesner- 
aceae. This has already been discussed generally on pages 6-8. 
The varying structural details from a two- to one-celled con- 
dition, as well as the diverse views expressed as to the affinities 
of such genera as Hyobanche, Lathraea, Christisonia that show 
wavering transition from two- to one-celled states, emphasize 
again the fact that here we are dealing with a condensing and 
simplifying variation. No such transition-relations are even 
suggested betw-een Gesneraceae and Orobanchaceae. 

In the different genera of the Orobanchaceae the fused mar- 
gins of the carpels grow inward to a varying degree from shallow 
marginal placentas to deep parietal, that approach central pla- 
centation. So the fundamental point of supposed affinities be- 
tween Gesneraceae and Orobanchaceae entirely breaks down, 
while a natural and continuous affinity between degraded par- 
asitic Scrophulariaceae and still more degraded Orobanchaceae 
has been established. 

Hairs of the Pistil 

The presence of hairs on the style and ovary in the different 
genera of the two families is not a constant feature. They differ 
as to number, distribution, and type. The following results 
were noted: 

In Gerardia aspera the hairs on the style, though present, are 
few in number. 

In species of Odontites the base of the style and upper part 
of the ovary are very hairy, while the upper part of the style is 
almost glabrous. The hairs are long, narrow and pointed. 



1 68 Boeshore — The Morphological Continuity of 

In Rhinanthus the hairs are numerous from the stigma down- 
ward but decrease in number toward the base of the style and 
finally disappear. They consist of one cell pointed at the dis- 
tal end on the upper part of the style, and of 2 to 3 cells on the 
lower part of the style, and are broad at the base, tapering grad- 
ually toward the tip. 

In Bartsia alpina the numerous one- to several-celled hairs 
are distributed along the entire style and the upper half of the 
ovarian surface, being most numerous on the ovary. They are 
quite long and needle-like in appearance. 

In Bellardia they are exceedingly numerous along the entire 
stylar surface, and consist of one needle-like cell that is dark in 
color. 

In Orohanche coerulea the glandular type of hair is seen along 
the entire style, similar to the hairs found on other parts of the 
plant already described. 

The style and ovary in the genera Aphyllon, Epiphegus and 
Conopholis are glabrous, although the stigmatic areas of the first 
two mentioned are covered with comparatively short unicellu- 
lar hairs. 

The Nectary 

The nectarv of Scrophulariaceae is described by Wettstein 
(30, p. 39) as hypogynous, ring formed or one-sided. Beck (31, 
p. 127) gives a similar description for Orobanchaceae. "Nektar 
absondernden Stellen am Grunde der Stf. oder am Grunde des 
Frkn. ringformige, oft buckelig, seltener beutelformig vorspring- 
ende Nektarien. " For Gesneraceae Fritsch describes the nectary 
as a "Discus" usually well developed, ring to cup-shaped, or as 
reduced isolated glands, which may be also one-sided. While 
these general descriptions fairly agree in the three families, most- 
ly one-sided nectaries are characteristic of parasitic Scrophulari- 
aceae and Orobanchaceae, as will now be taken up. 

In Melampyrum pratense "the nectary expands toward the 
lower lip into a whitish rounded body, on either side of which 
runs a nc tar-secreting groove." 

In M. linear e the nectary consists of a similarly rounded body 
placed to one side of the ovary. 

The general description of the nectary for Rhinanthus is given 
by Knuth. He says that nectar is secreted by the fleshy base 



Scrophulariaceae and Orohanchaceae 169 

of the ovary which projects to the front, and it is stored in the 
bottom of the corolla tube. In all the species examined by the 
writer the nectary agrees with this description, but further, it 
is curved inward at the top and points directly toward the ovary 
as a tongue-like process. 

In Bartsia alpina the nectar is secreted by a cushion-like 
swelling at the lower side of the base of the ovary, extending a 
little beyond as a rounded knob. 

Lathraea squamaria has a large, roundly triangular and some- 
what lobed nectary situated at the base of the ovary. 

In L. clandestina the ovary is laterally compressed and tra- 
versed bv a longitudinal groove, bearing in front a three-lobed 
nectary. 

One species of Orobanche, crenata, "secretes nectar at the 
orange-yellow base of the ovary." 

The nectary of Aphyllon is a small, rounded, whitish swelling 
at the base and a little to one side of the ovary. 

In Epiphegus the nectary appears as a swelling on one side 
of the ovarv, antero-laterally in position, just above the base. 

The nectary of Conopholis is a rudimentary ovarian gland. 

The Seeds 

The seeds vary in number from 4 in one capsule of some gen- 
era of the Scrophulariaceae, (Melampyrum, Rhinanthus) to very 
numerous (as many as 1500 in one capsule) in other genera of 
Scrophulariaceae and Orobanchaceae. Increase in seed number 
is usually accompanied by a reduction in size, so that the seeds 
become very small in such genera as Epiphegus and Aphyllon. 
In structural details, the seeds of the purely parasitic genera are 
simplified and most degraded; in some of them the embryo con- 
sists of a small group of undifferentiated cells {Aphyllon, Epi- 
phegus.) 

To supplement the writer's information, gathered from his 
own examination of material, Bentham and Hooker's "Genera 
Plantarum" (32, pp. 967-980) was used as the chief source for 
genera of Scrophulariaceae. 

The seeds of Rhinanthus are few in number, sub-orbicular, 
compressed, and surrounded by a wing-like structure. The 
embryo is small. 

Melampyrum has from 2 to 4 seeds which are smooth, and have 
an aril-like appendage at the base. 



170 Boeshore — The Morphological Continuity of 

In Gerardia, the seeds are numerous, oblong wedge-shaped 
or angular; the testa is loose-fitting. 

In Euphrasia, the numerous seeds are pendulous, oblong, 
with longitudinal ridges. 

In Bartsia, the seeds are many, pendulous, or may be numer- 
ous and placed subtransversely, with wings and longitudinal 
ridges. 

In Tozzia, the seeds are ovoid-globose; the testa is appressed; 
and the embryo is small. 

The seeds of Buchnera are very numerous and ovoid or oblong; 
the testa is reticulate, subappressed. 

In Harveya, the seeds are very numerous; the testa is heavily 
reticulated and loose; the embryo is equal to half the albumen in 
amount. 

In Hyobanche, the seeds are numerous, small, globose; the 
testa is loose, reticulated. 

Lathraea has numerous small seeds, spherical in shape, and 
the testa is wrinkled. 

In species of Orobanche, the seeds are numerous, reticulated, 
wrinkled or striate; the embryo is minute with cotyledons scarce- 
ly differentiated. 

In Christisonia, the seeds are extremely numerous, very small, 
and subglobose, and the testa is reticulated. 

In Aphyllon, the seeds are numerous, small, light, surrounded 
by a tough leathery coat of flattened cells with thick indurated 
walls; the endosperm cells are filled with starch and enclose a 
small embryo consisting of a group of undifferentiated cells. 

In Conopholis, the seeds are of fair size, numerous, and some- 
what quadrangular in shape; the embryo is small, undifferent- 
iated; and the testa is heavily thickened. 

In Epiphegus, the seeds are very numerous (from 700 to 1800) 
small, oblong in shape; the embryo is a group of undifferentiated 
cells; and the testa cells are elongated with much thickened 
walls. 

Selection of Hosts 

The less parasitic Scrophulariaceae have a rather wide range 
of hosts. The species of Gerardia parasitize on Grasses, Com- 
posites, etc., as has already been stated. 

For Bartsia, the following are given as hosts: Avena flaves- 
cens, Phleum pratense, Trifolium pratense. 



Scrophulariaceae and Orobanchaceae 171 

Tozzia parasitizes on the roots of Ranunculus, Petasites, Rumex, 
and Alchemilla. 

Poa, Avena, Luzula, Carex, Senecio, Trifolium, Capsella, Epi- 
lohium, and Festuca, are given by Heinricher as hosts of Euph- 
rasia. 

The roots of Lathraea may attach themselves to the roots of 
Ash, Elm, Poplar, Hornbeam, and Hazel as hosts. 

Species of Orobanche seem to have a very wide range of hosts. 
According to Koch (16), Orobanche minor may parasitize on 44 
species of plants; 0. ramosa on 29 species; 0. speciosa on 13 
species, and 0. hederae on 3 species. These hosts may be found 
amongst members of Papilionaceae, Geraniaceae, Cruciferae, 
Oleaceae, Ranunculaceae, and others. 

Although various species have been given as hosts of Aphyllon, 
the writer quite agrees with Smith in finding it to grow only on 
the roots of Aster corymbosum. 

Epiphegus has been found to grow only on the roots of Fagus 
americana. Conopholis similarly parasitizes on but the one 
genus Qnercus, and so far as the writer has learned on the group 
of the red oaks. 

The writer feels deeply indebted to Professor John M. Mac- 
farlane who first suggested the work and whose valuable criti- 
cisms, and assistance have been a source of constant encour- 
agement in the preparation of this paper. Thanks are due to 
Mr. W. R. Taylor for the photographs in Plate XVI, to Dr. F. 
W. Pennell for the use of several slides, and to Mr. H. W. Stout 
for locating a growth of Conopholis. 

Summary 

A short review of the evidences dealt with above might be 
put in summary form as follows: 

I. All macroscopic and microscopic details suggest that the 
parasitic Scrophulariaceae and Orobanchaceae form a contin- 
uous and parasitically degrading morphological series that show 
transitional steps from green nearly autotrophic plants like 
Melampynim, Rhinanthus, and Euphrasia to increasingly con- 
densed and degraded genera like Bartsia and Harveya, on to 
Lathraea, that has been shown to be placed by some botanists 
in Scrophulariaceae, by others in Orobanchaceae, thence through 
species of Orobanche to Epiphegus, and finally Aphyllon and 



172 Boeshore — The Morphological Continuity of 

Conopholis. No such continuity exists between the wholly 
green autotrophic Gesneraceae and Orobanchaceae, nor are any 
members of the Gesneraceae parasitic. 

2. During progressive parasitism in Scrophulariaceae and 
Orobanchaceae commencing parasitism consists in a few of the 
fibrous roots becoming enlarged toward their extremities into 
parasitic haustoria, while other roots are still autotrophic in 
relation. With increasing parasitism these secondary roots be- 
come shortened and the primary root also condenses into a cen- 
tral knob or swelling as can be traced successively in Gerardia, 
Lathraea, Orobanche, Epiphegus, Conopholis and Aphyllon. 
Ultimately, complete vegetative fusion and enlargements be- 
tween primary root and ascending vegetative axis result in the 
formation of a rounded tuber {Epiphegus) or greatly swollen 
rounded or oval mass {Conopholis) difficultly distinguishable 
from the enlarged roots of oak on which the last grows. 

3. In progressive degradation the elongated ascending leafy 
axis of Gerardia or Bartsia shortens steadily, and in Harveya and 
Hyobanche becomes a short axis bearing reduced nonchloro- 
phylloid foliage leaves. These are seen in Lathraea to become 
the characteristic scales investigated by numerous observers. 
In Orobanche the leafy axis is reduced to a short tuber that is 
separated from the condensed primary root by a constricted 
neck {0. cruenta), or the primary root and scaly axis become 
continuous as in 0. minor. This by progressive degradation 
becomes a slightly constricted root part below and a stem part 
above, covered by tooth-shaped leaf-scales, or an oval tuber on- 
ly, that is primary root below and tooth-scale stem above {Epi- 
phegus). In Conopholis even this distinction is largely oblit- 
erated. 

4. In the less parasitic types, e. g., G. flava, the leaves are 
large green and actively vegetative, but by gradual stages be- 
come in time small and scale-like in G. aphylla. In Harveya 
and Hyobanche they are scattered along 2 to 6 inches of the con- 
densing axis. In Lathraea, these scales are largely underground 
colorless, or purplish-white, and extend over i to 3 inches of the 
vegetative shoot. In Orobanche the brown, yellow or red scales 
cover the short tuberous vegetative axis for one to one-fourth 
of an inch. The same is true for Epiphegus, or the scales are 
rather shorter for Aphyllon. In Conopholis the intimate fusion 



Scrophulariaceae and Orobanchaceae 173 

of root and vegetative axis has resulted in practical obliteration 
of any distinction of parts. 

5. The inflorescence axis from being greatly elongated to 
constitute a several- to many-flowered raceme becomes a rela- 
tively simplified axis with a reduced number of flowers, the cli- 
max of which is reached in Conopholis, which bears a spike with 
40 to 10 flowers. In Aphyllon each inflorescence is represented 
by a single flower. 

6. It has been shown that the histological details, of stem and 
leaf in the above progressive series of degrading parasitic types, 
agree fundamentally with and verify the naked eye characters. 

7. The sepals of Scrophulariaceae and Orobanchaceae have 
been found to show fundamentally similar structures and at 
times to show similar condensation in the former from a five- 
leaved to a four-leaved calyx through absorption of the odd se- 
pal, as in Tozzia, Euphrasia and others. Lathraea, as an inter- 
mediate type, may have a five to four-lobed calyx, and finally, 
species of Orohanche and Boschniakia may show five to three se- 
pals making up the calyx. 

8. In structure the stamens have been shown to constitute 
an important link in the chain of evidence, for in all Gesneraceae 
the anther lobes more or ]ess converge and press against each 
other at the apex and are rounded, as well as often divaricate at 
their bases. In Scrophulariaceae and Orobanchaceae the mac- 
roscopic and microscopic details proclaim progressive modifi- 
cations in that the bases of the parallel anther lobes grow down- 
ward into stifT awn-iike horns, whose terminal cells are similarly 
thickened throughout the series, and show a similar mode of 
unequal thickening. In pollination, therefore, authors like 
Ogle, Miiller, and Knuth demonstrate similar pollination ar- 
rangements for Scrophulariaceae and Orobanchaceae that diflfer 
markedly from those in Gesneraceae. 

9. Histologically, the sepals and stamens have been shown in 
many of the types to bear tapered multicellular hairs inter- 
spersed with capitate-glandular hairs that suggest strongly an 
origin in common. 

10. The nectary in Gesneraceae is a cylindric structure that 
appears either as a simple girdle, or as a series of connected 
nectariferous knobs; very rarely is it a median unpaired swell- 
ing. In Scrophulariaceae and Orobanchaceae the nectary is 



174 Boeshore — The Morphological Continuity of 

often a median knob in line with the antero-posterior axis of the 
flower, or somewhat displaced. 

11. Evidence has been given to show that while the ovary is 
two-celled in Scrophulariaceae and usually one-celled with deep 
to shallow placentas in Orobanchaceae, all transitions between 
these can be traced from Harveya and Hyobanche to Lathraea 
clandestina and Christisonia albida, etc. 

12. As to seeds, these are few (4-12) and fairly large in the 
less parasitic Scrophulariaceae, becoming decidedly small and 
numerous in Harveya and allied types of Scrophulariaceae as 
well as in all of the Orobanchaceae. 

13. In structural details and morphological complexity the 
seeds show continuous degradation changes from the less para- 
sitic genera of Scrophulariaceae to the most degraded genera of 
Orobanchaceae, such as Aphyllon and Conopholis, in which a 
rudimentary endosperm and formless embryo are alone devel- 
oped up to the time of germination. 

14. Physiologically it has been shown that in transition from 
the less parasitic Scrophulariaceae, like Odontites and Gerardia 
which parasitize on a variety of hosts, transitions are shown to 
genera like Orobanche, some species of which seem to confine 
their parasitism to the species of a family or even to the species 
of a genus, as pointed out by Beck (p. 31), while finally in such 
a highly degraded type as Epiphegus abundant evidence shows 
it to be purely parasitic on Fagus americana, Aphyllon to be 
similarly wholly parasitic on Aster corymbosum, and Conopholis 
on one or two species of Qiiercus. 

Conclusions 

From a review of the above observations, the writer believes 
that ample evidence has been adduced to show that direct and 
distinct continuity can be established from non-parasitic through 
semi-parasitic Scrophulariaceae to the most degraded parasites 
of the family, and that these again show direct continuity with 
the still more degraded and condensedly parasitic types of Oro- 
banchaceae. 

Alike logically and biologically, therefore, the two types 
should be treated in continuous descending series from the high- 
est to the most degraded genera. 



Scrophiilariaceae and Orohanchnceae 175 

Explanation of Plates. 

Key to the lettering of Figures 1-16. 

r — The primary root from which are giv'en off secondary rootlets. 

st — Stem. 

hr — Host root 

fl — Foliage leaf. 

fs — Foliage scale. 

i — Inflorescence axis. 

Plate XII. 

Fig. I. Root system of Gerardia fiava showing parasitic attachment. 
(From a drawing by Mr. J. Stauffer in Gray's "Structural Botany.") 
Fig. 2. Root system of Gerardia purpurea. Natural size. 
Fig. 3. Root system of Gerardia aphylla. Natural size. 
Fig. 4. Root system of Orobanche minor. 

Plate XIII. 

Fig. 5. Root system and part of stem of Orobanche minor attached to 

clover root. (After Koch). 
Fig. 6. Stem and root system of Aphyllon uniflorum parasitic on the 

roots of Aster corymbosum. Natural size. 
Fig. 7. Tuberous swelling consisting of stem and root system of Epi- 

phegus virginiana. Natural size. 
Fig. 8. Stem and root system of Orobanche cruenta with constricted neck 

at the junction of stem and root. Natural size. 
Fig. 14. Root, underground stem, and lower part of inflorescence axis 

of Lathraea japonica. (X H)- 
Fig. 15. Orobanche minor. Note the short condensed stem, from i 

downward, as compared with that of Lathraea. (X H)- 
Fig. 16. Aphyllon. Stem still more condensed and shorter than that 

of Orobanche. (X K)- 

Plate XIV — Note the gradual condensation and shortening of stem in Figs. 
9-13. Foliage leaves become scales. 
Fig. 9. Gerardia flava. (X 34)- 
Fig. 10. Gerardia aphylla. (X %)• 
Fig. II. Gerardia aspera. (X M)- 
Fig. 12. Harveya capensis. (X J^). 
Fig. 13. Hyobanche. (X 14)- 

Plate XV — Figures 17-27 show the downwardly-directed processes at the 
base of the anther lobes. (X 10). 
Fig. 17. Stamen of Gerardia flava. 
Fig. 18. Stamen of Gerardia purpurea. 

Fig. 19. Stamen of Harveya coccinea. Note the elongated sterile an- 
ther lobe. 
Fig. 20. Stamen of Bartsia. 
Fig. 21. Stamen of Melampyrum. 



Fig. 


22. 


Fig. 


23- 


Fig. 


24. 


Fig. 


25- 


Fig. 


26. 


Fig. 


27- 


Fig. 


28. 


11 


5). 


Fig. 


29. 



176 Boeshore — llie Morphological Continuity oj 

Stamen of Conopholis, front and back views. 

Stamen of Epiphegus, front and back views. 

Stamen of Gerardia aphylla. 

Stamen of Oroha^iche minor. 

Stamen of Orobanche coerulea. 

Stamen of Aphyllon uniflorum, front and back views. 

Epidermal cells and stomata on a scale of Conopholis. (X 

Transverse section of the awn-like horn at the base of an an- 
ther of Aphyllon. The epidermal tissue shows cells with the outer and 
radial walls much thickened in u-shaped manner. (X 115). 
Fig. 30. A longitudinal section of the awn-like horn of an anther of 
Aphyllon.. (X 115). 

Plate XVI. 

Fig. 32. Aerial flowering shoots of Conopholis showing attachment at 
the base to the swelling on the oak root. Originally there were 40 
shoots growing from the one swelling. (X K)- 

Fig- 33- Tuberous swelling on oak root showing the numerous excres- 
cences from which the flowering shoots arise. (X H)- 

LITERATURE CITED 

1. Wettstein, R. Die natiirlichen Pflanzenfamilien IV. 3. B, 1895. 

2. Beck, G. R. Die natiirlichen Pflanzenfamilien, IV. 3. B, 1895. 

3. Fritsch, Karl. Die natiirlichen Pflanzenfamilien IV. 3. B, 1895. 

4. Baillon, H. Histoire des Plantes, X, 1891. 

5. Le Maout, E. and Decaisne, J. Descriptive and Analytical Botany, 
English Translation, 1876. 

6. Warming, E. A Handbook of Systematic Botany, 1895. 

7. Heinricher, E. Die griinen Halbschmarotzer. Jahrbiicher fiir wis- 
senschaftliche Botanik, 32, 1898. 

Die griinen Halbschmarotzer. Jahrbiicher fiir wissenschaftliche Botanik, 
36, 1901. 

8. Solms-Laubach, H. Ueber den Bau u. die Entwicklung parasicischer 
Phanerogamen. Jahrbiicher fiir wissenschaftliche Botanik, 6, 1867-68. 

9. Beck, G. R. Monographic der Gattung Orobanche. Bibliotheca Bot- 
anica, Heft 19, 1890. 

10. Koch, L. Die Entwicklungsgeschichte der Orobanchen, 1887. 

11. Henderson, M. W. Contributions from the Botanical Laboratory 
of the University of Pennsylvania, V, 19 19. 

12. Beck, G. R. Die natiirlichen Pflanzenfamilien, IV. 3. B.. 1895. 

13. VVorsdell, W. C. On the Comparative Anatomy of Certain Spec- 
ies of the Genus Christisonia. Annals of Botany. IX, 1895. 

14. Kerner, a. The Natural History of Plants, translated by Oliver, 
I, 1895. 

15. Kerner, A. The Natural History of Plants, translated by Oliver, 
I. 1895. 

16. Koch, L. Die Entwicklungsgeschichte der Orobanchen, 1887. 



Scrophulariaceae and Orohanchaceae 177 

17. Cooke, E. and Schively, A. F. Observations on the Structure and De- 
velopment of Epiphegus virginiana. Contributions from the Botanical Lab- 
oratory of the University of Pennsylvania, II, No. I, 1904. 

18. Smith, A. C. The Structure and Parasitism of A phyllon uniflorum , 
Gray. Contributions from the Botanical Laboratory of the University of 
Pennsylvania, II, No. I, 1904. 

19. Koch, L. Die Entwicklungsgeschichte der Orobanchen, 1887. 

20. WoRSDELL, W. C. On the Comparative Anatomy of Certain Spec- 
ies of the Genus Christisonia. Annals of Botany, IX, 1895. 

21. Gray, A. New Manual of Botany, Seventh Ed., 1908. 

22. Wettstein, R. Die natiirlichen Pflanzenfamilien, IV, 3. B, 1895, 
22,. Kerner, a. The Natural History of Plants, translated by Oliver, 

L 1895- 

24. Solereder, H. Systematic Anatomy of the Dicotyledons, trans- 
lated by Boodle and Fritsch, I, 1908. 

25. Wilson, L. L. VV. Observations on Conopholis Americana, Contri- 
butions from the Botanical Laboratory of the University of Pennsylvania, II 
No. I, 1904. 

26. Ch.\tin, G. a. Translation in Solereder's "S>stematic Anatomy of 
the Dicotyledons," I, 1908. 

27. Le Maout, E. and Decaisne, J. Descriptive and Analytical Bot- 
any, English translation, 1876. 

28. Cooke, E. and Schively, A. F. Observations on the Structure and 
Development of Ephiphegus virginiana. Contributions from the Botanical 
Laboratory of the University of Pennsylvania, II. No. I, 1904. 

29. Knuth, p. Handbook of Flower Pollination, III, 1909. 

30. Wettstein, R. Die naturlichen Pflanzenfamilien, IV, 3. B, 1895. 

31. Beck, G. Die natiirlichen Pflanzenfamilien, IV, 3. B, 1895. 

32. Bentham, G. and Hooker, J. D. Genera Plantarum, II, 1876. 



Bol. Contrih. Univ. Pont. 



Vol. V, Plate VI. 




Taylor ox Reproduction ix Acer. 



Bot. Contrib. Univ. Penn. 



Vol. V. Plate VII. 




Taylor on Reproduction in Acer. 



Bot. Contrib. Univ. Pcvn. 



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46 ^ 42 \J 45 

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BOESHORE OX SCPOPHULARIACEAE AND OROBANXHACEAE 



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BOESHORE ON SCROPHULARIACEAE AND OrOBANCHACEAE 



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