1915.
13

BOTANICAL CHARACTERS OF THE LEAVES OF

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June 23

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Forms for the Observer’s Use
Application of the System to the Degiet
Noor Variety and Its Seedlings

. A. TAYLOR, Chief

CONTENTS

PROFESSIONAL PAPER

BULLETIN No. 223
Contribution from the Bareau of Plant Industry
Breeding Investigations

ING CULTIVATED VARIETIES
By

D STATES DEPARTMENT OF AGRICULTURE
THE DATE PALM USED IN DISTINGUISH-

SILAS C. MASON, Arboriculturist, Crop Physiology and

.

Washington, D. C.
Use of the Field Protractor

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BULLETIN OF THE

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No. 223 ye

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Contribution from the Bureau of Plant Industry, Wm. A. Taylor, Chief.
June 23, 1915.

(PROFESSIONAL PAPER.)

BOTANICAL CHARACTERS OF THE LEAVES OF THE DATE
PALM USED IN DISTINGUISHING CULTIVATED VARIETIES.

By Sizas C. Mason, |
Arboriculturist, Crop Physiology and Breeding Investigations. —

CONTENTS.
Page. Page.
Introduction. 2, <1 -.45 on jnauassopsoueeesis 1 | Forms for the observer’s use...............-- 13
The date tres. 2.5 ss case ckg encores eee se 3 | Application of the system to the Deglet Noor
Leaf characters of the date............-....- 3 variety and its seedlings...............--.. 16
Use of the field protractor.....-......-..--.- 13
INTRODUCTION.

At the present time most students of the date rely largely, if not
wholly, on the. fruiting characters for means of distinguishing the
numerous varieties. Z

While it is recognized that in the Old World date-growing countries
the natives distinguish almost intuitively the different varieties of
dates by the tree habit and leaf characters, but little attention has
been given to these points by European and American students of the
date and no attempt has been made to systematize these characters.

The date trees certainly possess such characters, and the varietal
distinctions are as constant in the trunk and leaf as they are in the
fruits. %

From the beginning of the study of the imported date trees in the
American gardens there has been felt the need of a method of com-
paring and describing the different trees in the absence of their fruit
and independently of their fruit characters.

This becomes of importance in assisting date work along two very
distinct lines—the identification and comparison of varieties, either
imported or originating in this country, and the study of seedlings
originating from the cross-pollination of different varieties.

/Note.—This bulletin is of interest to date growers, especially in the Southwestern States.
87664°—Bull. 223—15——-1

Missouri B TAMICAL
@seneed Cppnany

2 _— BULLETIN 223, U. S. DEPARTMENT OF AGRICULTURE.

To enable the observer to make such foliage comparisons in a pre-
cise and systematic manner, capable of tabulation for future refer-
ence, is the most important use to which this study of degeemeee
characters can be put.

Most of the workers in the date gardens of the Department of Agri-
culture soon learn to recognize the more prominent varieties by such
obvious characters as a slender or a heavy trunk; leaves with broad
or narrow rib bases, erect and rigid in growth or more or less spread-
ing, feathery, and graceful. Less elementary characters are recog-
nized, but not formulated, which would distinguish two varieties which
might agree in the more fundamental points. There are differences
in the broad outlines of the leaf blade as a whole and differences in the
blade, as to whether it is smooth and nearly flat or whether from
varying angles of the pinne it appears on the defensive with bayonet-
like points thrust out in all directions, as if to resist assault. __

Most persons who become familiar with date trees will distinguish
between trees of varieties which possess many characters in common
if they are side by side for comparison; fewer will be able to keep the
resemblances and differences in mind if the compared trees are on
opposite sides of the garden, and a still smaller number will be able to
keep varietal characters clearly in mind in going from one locality to
another.

The object of this study has been to ——— just what varietal
characters in date trees consist in; then to apply names and formulate.
these so that they may be used in classifying and determining varieties,
much as floral and foliage characters are used by the systematic

botanist.

Perhaps of all cultivated plants the date palm is se most mechan-
ical or geometrical in its external structure. The cylindrical, col-
umnar trunk has the overlapping leaf bases, like inverted tiles,
arranged in broad right or left spirals. The rachis: or rib, is long,
smooth, and rodlike, and its expansion toward the base is along
symmetrically molded surfaces.

The leaflets, or pinne, are in symmetrical ranks from either side of
the rib, and each individual has its polished sword-shaped blade folded
lengthwise with the precision of machine work. In the unopened leaf
the pinnz are placed with the compactness of the ribs of a fan, and in
expanding each assumes within certain limits a definite angle wath
the rachis peculiar to its class.

Having such features to deal with, the writer feels that no Farilicr
explanation is needed for the very mechanical way in which the sub-

ject of date-tree characters is treated. It is the caged method by
which the subject can be approached,

CHARACTERS OF THE LEAVES OF THE DATE PALM. 8

THE DATE TREE.

Date trees. have no true branches, but during their earlier years,
and under some conditions up to a considerable age, buds are pushed
in the axils of the leaves and later develop into suckers or offshoots.
These, if left undisturbed, may form trunks and tops of their own
and grow to a size second only to the parent tree and identical with
it in leaf and fruit characters. When these offshoots are removed
at a proper size and planted by themselves they afford the only
means we have of propagating the parent variety true to type.
(See Pl. I.)

The flower stalks of the date are produced from the axils of the
leaves in similar positions to those in which the offshoots are pro-
duced.

While many genera of palms have either perfect or monccious
flowers, all species of the genus Phoenix are dicecious, the male and
female flowers being borne on separate trees. In rare instances both
pistillate and staminate flowers are produced on the same spike.*

In noticing a date tree closely, one finds only a central columnar
trunk, from the one bud at the top of which new leaves are pushing
out, while around its sides the older leaves clasp the stem with their
broad-sheathed bases. If the tree has reached some age and the
trunk has gained a few feet in height, the older lower leaves will
probably have been cut away, leaving a foot or more of their bases
arranged in orderly position around the trunk in the manner of
reversed tiles. Closely wedged in between these are dozens of sheets
of very tough, coarse-matted fiber, called ‘‘leef’’ by the Arabs,
the remnants of the leaf sheaths. (Pl. II.) The real trunk of the
date tree is inside of these and is greatly strengthened and protected
by them. It is strengthened and supported by the wrapping of
their tough fibers against the leverage of the desert winds, which
exert a powerful pressure upon the broad top. It is protected from
bruising and battering or the gnawing of grazing animals, and
insulated alike against the intense heat or the sudden freezing
weather of the winter months, which may descend upon even a
<= desert.”

LEAF CHARACTERS OF THE DATE.

Upon a casual examination of a date leaf the most obvious feature
is the long flexible blade, which may vary in length from 3 or 4 feet
in a young plant to 9, 12, or even 16 feet in a tree of mature BOs

(PI. III.)

1 As the various species of this genus hybridize readily with one another, the so-called date palms grown
in many nurseries and sold for ornamental planting in California and Florida are often crossed to such
an extent that the true dactylifera characters, as found in the trees obtained from the Sahara, are difficult
to recognize, and the application of the rules laid down in this bulletin to such would lead to confusion.

2 Date trees ia Arizona and California subject for a few hours to a temperature of 15° or 18° F. may have
the outer leaves killed, or at 12° F. all exposed leaves may be killed and the protected bud or growing
point of the tree remain uninjured, so that new leaves are pushed from the center when spring opens.

4 BULLETIN 223, U. S. DEPARTMENT OF AGRICULTURE.

| The axis of this blade is a stout polished rib, technically called
the rachis, which may be several inches broad where the leaf is
attached to the trunk, but tapers to a slender tip of less than a
‘quarter of an inch. (See Plate I.) As the leaves are placed on the
trunk the face of the leaf, which is inward or toward the center of
the tree, may be called the ventral surface. The reverse of this,

_ away from the tree, is the dorsal surface. The right and left sides

will be designated with the leaf in a vertical position and with the
_ observer facing the trunk.
Tf an entire old leaf is cut away at its attachment to the trunk it
will be found that the thick, wedge-shaped base shows torn and
_ ragged margins, or perhaps a bit of matted fiber still clinging to it,
_ where the fibrous sheath has been torn away. At the line of attach-
ment sheets of this fiber encircle the tree. If a date palm be dis-
sected, cutting away leaf after leaf till we get toward the bud, we find
leaves with their original structure entire and the margins of sie wide
base of the rib thinning out to a continuous mat of brown fibers, which
forms a complete sheath encircling all the younger growth. As the
area of active growth is approached, near the center this sheath will
be yellowish white, soft, and succulent, not more than 2 or 3 inches
in diameter, and 8 inches or a foot in length. In a large tree the
- sheath may be 20 inches or more in length. On the opposite side
from the rachis the margin of the sheath has an upward expansion
into a broad lingua, or tongue, with coarsely incised margins and a
_ blunt-pointed or an acuminate apex, which sometimes protrudes
several inches against the inclosed leaves and which varies in a manner
somewhat characteristic of different varieties. The diagonal arrange-
ment of the fibers allows the sheath to expand a good deal, but the
continual pushing upward of new leaves from within and the expan-

sion of the trunk finally rupture it or tear it loose from the sides of the —
yib. Its lower margin remains attached to the trunk, so that this —

wrapping of old sheath fiber may persist for many years. In rare
instances, the variety Lagoo, for example, the sheath has ear-shaped
or auriculate expansions at the upper margin of its attachment to
the rachis. Figure 1 shows a typical date leaf with the various parts.
An entire leaf comprises the upper expanded portion, properly
called the blade, which includes the length from the first spines to the

top, and the lower portion, representing the petiole, including the —

broad, wedge-shaped base of the rachis and the sheath. The blade

is divided into the spine area and the pinne area, the exact separation
of which sometimes can be only approximated. Varieties differ
greatly in the proportion of the leaf blade occupied by the spines,

which may range from 18 or 20 per cent to 45 per cent of the entire
blade length.

|
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Bul, 223, U. S, Dept. of Agriculture. PLATE I,

A 9-YEAR-OLD DATE TREE IN THE COOPERATIVE DATE GARDEN, TEMPE, ARIZ.

A large number of offshoots, shown both at the base of the trunk and on its sides, are
trimmed up and ready for removal.

Bul. 223, U. S. Dept. of Agriculture. PLATE Il.

[Pom

FES Ang
Fe gm \ yh
‘ ‘ ha

A 20-YEAR-OLD MALE DATE PALM IN THE MECCA COOPERATIVE DATE GARDEN,
Mecca, CAL.

PLATE III.

, U.S. Dept. of Agriculture.

223

Bul.

Supund Joye srvad 0 UMOYS O18 S99T} OTL, “SUIPTING Ooo aT} Jo yoor oY] ULOIT Ysa SUPYOOT AOTA

‘Zldy ‘SdW3L LV N3GYV5 3Lvq 3AILvuado009

Bul. 223, U. S. Dept. of Agriculture. PLATE IV.

A Hayany DaTe TREE, 10 Years OLD, AT THE TEMPE COOPERATIVE DATE GARDEN.

This tree shows a number of offshoots on the trunk, 3 or 4 feet from the ground; also graceful
foliage and long, flexible ‘ribbon ” pinne,

CHARACTERS OF THE LEAVES OF THE DATE PALM, 5

The broad outlines of the blade vary considerably with different

varieties and are determined
by the length of the pinne
in different parts of the blade
and the angles which they
form with the rachis and
plane. To illustrate: If in a
given leaf the pinne at the
middle of the blade are 16
inches long and placed at
right angles, or 90°, with the
rachis and lie in the plane of
the blade; that is, so that
the leaf is flat, the leaf will
be 32 inches broad, not count-
ing the breadth of the rachis
fig. 2, A,bb). Let the same
length of pinne be placed in-
clined only 45° from the
rachis and still in the plane
of the blade, then the blade
will be but 22% inches broad
(fig. 2, A, ce). But let the
pinne, instead of lying flat
(fig. 2, B, b) diverge 45° from
the plane of the blade, as well
as 45° from the rachis (fig. 2,
B,c), then the leaf blade be-
comes a V-shaped trough only
16 inches broad, or half the
breadth of the blade with the
pinne flat and at right an-

gles. ;
_ A close inspection of the
rachis of the date leaf shows

that it is irregularly four-

sided; the inner or ventral
surface is usually strongly
arched or at the first spines
is made up of two ogee curves
turned together. The back
or dorsal surface is moder-
ately or often strongly

PINNAE AREA

Fig. 1.—A typical date leaf, showing its various parts.

rounded at the base, slightly rounded or rarely flattened toward the

6 BULLETIN 223, U. S. DEPARTMENT OF AGRICULTURE.

top. The sides or lateral faces are flat or somewhat concave, and
their inner margins, at first slightly converging, as they approach the
top are drawn so near together as to give a triangular cross section
to the rib.
The characteristic form or habit of tree tops of each date variety,
due to the curves of the leaf blades, is largely determined by the
flexibility of the

e rachis. This is gov-

Y erned in part by the

B .% degree of firmness and

a/ \ elasticity of the fiber

a a _ of the rachis, but

more by the way in
which the diameter
diminishes along the
different faces.

The feathery grace
of the Areshti variety
is due to the leaves

Peer. aa

able rigidity in the
lower portion, but
with the rachis di- -
minishing to a deli-
cate and slender flexi-
bility at the apex.
The broad, open top
and loose, lazy curves
of the Rharsleaves are
. due to a rather rapid
diminishing in the di-
Fig. 2.—Diagram showing how the size of the date leaf is affected by meter of the rachis a
the angles which the pinri form with the rachis. A representsthe short distance above
leaf as lying flat, the dotted lines (b b) showing the breadth the leaf ki .
would have with the pinnz at 90° of axial divergence, the solid lines the base, yet main-
(ec) showing the breadth of the leaf with pinne diverging 45° from taining too much size
theaxis. B represents a cross-section view of the leaf,bshowing the . - ‘
pinne lying in the blade plane, or flat, but with an axial divergence 10 the apical portion

of 45°; ¢ shows the same pinnz also diverging 45° from the blad i iri
plan P verging 45" trom the blade =o give grace OF Sir-

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Pek +297 13

ness. In the Thoory

and other varieties of that class the thick, strong rachis holds its size

and rigidity well up in the blade, curving only when forced out by

the growth of the inner leaves. Such trees have a stiff and uncom-
promising aspect through the entire top.

The relative size and form of the rachis in different portions of the

blade are so characteristic in the different varieties and such impor-

maintaining consider- __

ania RerCnEne dia enuenn eee”. eeenuaEanneaeinS -Aemeeha MIRE .. samen

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CHARACTERS OF THE LEAVES OF THE DATE PALM, 7

tant factors in determining the form assumed by the tree top that it
has been thought worth while to make outline tracings of the cross
sections of the rachis of leaves of the different varieties, four series of
which are reproduced with the descriptions of the respective varieties
as text figures in this bulletin. (See figs. 11, 13, 14, and 15.) The
first section is in all cases made just below the lowest spines; that is,
at the base of what has been defined as the blade of the leaf, the others
1 or 2 feet apart to the apex or near it.

THE PINN2.

The organs commonly called leaflets, or properly pinne, of the date
leaf, including those suppressed as spines, number from 50 or 60 to
130 on each side of the rachis. The two sides of the leaf are fairly
symmetrical as to the length of the pinne blades and the angles at
which they are placed with the rachis, but not quite symmetrical in
numbers, there sometimes being a difference of four or five pinne on
opposite sides of the leaf. While the occurrence of pinne in pairs
is not infrequent, it appears to be largely accidental, and with the
general irregularity of their positions they can not be regarded as
being paired and opposite in position in the sense in which the mem-
bers of many compound leaves are so recorded.

The pinne are borne on the lateral faces of the rachis, with normally
a single pinna at the apex. In Plates I and IV the terminal pinnz
show very plainly on a number of leaves.

On the lower part of the blade the leaflike pinne are replaced by
stiff acute spines, from 1 inch to 7 or 8 inches in length. These are
really modified pinne, as is clearly shown by the channel in one side
corresponding to the fold of the pinnzw blade; also by their mode of
attachment and arrangement in groups. The larger spines pass by
gradations into stiff spinelike forms, which will be called spike pinne.
Above these there are in some varieties extra long, narrow forms,
so thin and weak as to be pendulous, which will be referred to in
descriptions as ribbon pinne. In Plate IV the long, pendulous ribbon
pinnex can be noticed on the lower portion of several leaves.

Each pinna consists of a green, leathery, sword-shaped or ensiform
blade, folded lengthwise, and a cushiony expansion or callus, called
the pulvinus, by which it is attached to the rachis.

In a few varieties the lower pinnez and some spines do not immedi-
ately broaden beyond the pulvinus into the thin blade, but have a
short, solid, necklike portion, elliptical i in cross section, for which
the name collum (Latin for ‘‘neck’’) is proposed.

Toward the upper end of the leaf in certain varieties the folds of
the pinne blade are somewhat unequal, the lower or proximal fold
being a little broader than the upper one. Instead of being inserted
directly into the rachis it is attached along the side, running down-

$7664°—Bull, 223—15——2 2

8 BULLETIN 223, U. S. DEPARTMENT OF AGRICULTURE.

ward (decurrent) along the lateral face for an inch ortwo. With the
fold of the blade slightly broader than the face of the rib, a free wing
results, and a series of these with corresponding wings from the oppo-
site side of the rachis may form a narrow channel along the middle
of the inner face of the leaf. When such wings and channels are
conspicuous they constitute good varietal characters and also are
of some importance in affording harbors for scale insects, particularly
Phoenicococcus marlatti.

When the new leaves issue from the center of the crown, three,

making a complete circle of the stem, usually follow in close succession
_ and are crowded into the form of an irregular cylinder. This gives to
each emerging leaf the form of a third of a cylinder with an acumi-
nate apex, the pinne being folded as compactly as the ribs of a fan
upward against the rachis. With
the expansion of the rachis the
pinne diverge and the cushiony
pulvinus at the base of each, at
first scarcely noticeable, rapidly
expands, pushing the pinna to its
characteristic angle and holding
it there securely.

ANGLES OF PINN4E WITH THE RACHIS.

The difference ik appearance of

Fig. 3.—Diagram showing the construction of imag-
inary planes bisecting the date leaf longitudinally ,
by means of which the angles of divergence of the
pinnz from the rachis are read: PR, Plane of the
axis, which would divide the leaf into right and

left halves; PB, plane of the blade, dividing the —

leaf into dorsal and ventral halves.

the leaves of varieties of dates is
largely due to the different angles
at which the pinne diverge from
the rachis. At first sight these
are confusing and are best under-

stood by constructing two imag-
inary planes parallel with the leaf and vertical to each other. (See
fig. 3.) Note (1) the plane of the blade (PB), which would divide the
leaf into an inner or ventral half and an outer or dorsal half, and (2)
the plane of the rachis (PR) at a right angle to the first and dividing
the leaf into right and left halves.

_Tf all pinne lay in the first plane there would be only two ranks, a
right and a left rank, and the blade would be broad and flat, its out-

lines determined by the length and axial angles of the pinne. If the -

pinne were inserted vertically or at 90° to the second plane, they
would project from either side like the teeth of a double comb.

Actually but few pinne in Phoenix dactylifera lie in either position,
but the exact position of any pinna may be recorded with precision
by determining its angle with each of these two planes.

=

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CHARACTERS OF THE LEAVES OF THE DATE PALM. 9

It is not to be supposed that date leaves are so perfectly laid off
along geometric lines that we have but to read a set of angles, refer
to a table; and say with confidence, ‘‘this is Thoory,” or ‘‘this is
Hayany.” But it is true that certain ranges of angles are found
only in certain varieties, and, along with other characters, are impor-
tant factors in Eantiieation.

PINN4E CLASSES.

A third character in the insertion of the pinne remains. In all
species of the genus Phoenix the folded pinne are attached to the
rachis, with the margins and channel inward, or toward the ventral
face of the leaf, and in some species, as Phoenix canariensis, they are
quite uniformly attached with the channel directly inward, or at
right angles with the blade plane.

In the date palm, while all the pinnez face generally inward, or
ventrally, only a portion of them face directly inward or at right
angles to the blade plane. An important class of them are placed
facing obliquely forward or upward, and about an equal number
face obliquely backward or downward, thus giving three distinct
classes of pinne as to position.

Those with the fold facing directly inward, or attached at right
angles with the rib, will be called introrse,' using a botanical term
meaning ‘‘directed inward.”

A second class includes pinnz with the channel directed obliquely
upward, or toward the apex of the leaf, and for these the term
antrorse,? meaning ‘‘directed upward or higher. ” will be used.

In a third class the pinne have the channel directed more or less
obliquely, downward, or toward the base of the leaf, and the term
retrorse,? meaning ‘‘directed back or downward,” will be applied
to these.

PINN GROUPS.

Studying the pinnez along the side of a leaf, we soon notice that
these classes of pinne are not placed at random, but that there is a
regularity in their succession. In other words, the pinne along the
respective sides of the rachis are arranged in groups of two, three,
four, or, rarely, five, a group of two being the most common. These
groups fall into regular and irregular classes. The regular groups,
which constitute the normal or regular form of arrangement, consist
of a lower or proximal antrorse pinna and an upper or distal retrorse
pinna, between which may occur one, two, or, rarely, three introrse
pinne. Figure 4 shows the ventral surface and left side of a section
of a rachis with the pinne cut to about an inch long. There are

1 “‘Introrse, intror’sus (Mod. Lat.), turned inward, toward the axis.”

2 Antrorse, antror’sus (antero-, before, versus, turned toward), directed upward, opposed to retrorse.”’

3 Retrorse, retror’sum (Lat.), directed backward or downward.” (Jackson, A Glossary of Botanical
Terms.)

10 BULLETIN 223, U. S. DEPARTMENT OF AGRICULTURE.

four paired groups in succession, each of an antrorse pinna (@) and a
retrorse pinna (7).

Figure 5, A, shows a ventral view of a section of a leaf, on the
left side (ZL) of which, from below upward, is a triple group (a, 7, 7)
and a paired group (a,r). On the opposite side (/) is a paired group
below and a triple group above.

In figure 5, B, the right-hand side of a section cut well toward the
top of the leaf shows a triple group below and a quadruple group
above. It should be noted that the antrorse and retrorse pinne are
not placed as obliquely as in those near the base of the blade.

In figure 5, C, the left-hand side of a section in about the middle of
the blade shows a group of five pinne (a, 7, 7, 7, 7). This group is
found in comparatively few varieties and only in small numbers.

Thus, there are four kinds of these regular groups. Noting them
by the initial letters of the component pinne, they are, first, the

Fic. 4.—Section of a date leaf, showing the rachis and the bases of four paired groups of pinnz, each group
comprising an antrorse pinna (a) and a retrorse pinna (r).

simplest and most common paired group of an antrorse and a retrorse
pinna (expressed as a, r); the triple group, with one intermediate
introrse pinna (expressed a, 7, r); the quadruple group, pouding
two introrse pinne (a, 7,7, r); and the quintuple id, 3; 4, te

Of irregular groups of pinne there is a great variety—a, 7; a, 1, i;
a,a,7r; 4,7, 7; a,1, 4, r, ete. Often toward the apex of the blade the
groups Geccmne obscured and the classes not well defined, merging
into introrse pinnx. In some varieties there is, especially toward
the apex of the blade, a decided uniformity in leaflet insertion, the
antrorse and retrorse pinne nearly disappear, and the groups are
not well defined.

Figure 5, D, shows the left side of asection from a leaf of Areshti, cut
near the top. Here no definite grouping could be made. The first,
fourth, fifth, and seventh show a slightly oblique retrorse position,
but such an area would be recorded as ‘‘indefinite.”’

In these the blade has nearly a plane surface, the pinne falling
most nearly into two ranks. Where the grouping is most pro-
nounced, six distinct ranks.of pinnz can be discerned, three on either
side of the rachis. This is best noted by looking from the apex down

~~. Sygate

CHARACTERS OF THE LEAVES OF THE DATE PALM. 11

the trough, or valley, of the blade, the rib being on a level with the
eye. The 6-ranked leaves have a ragged and aggressive appearance,
and with their formidable thorns and acute pinna tips are most com-.
pletely armed against predatory animals.

Examining the pinne of the three classes—antrorse, introrse, and
retrorse—we find that each has its well-defined relative position of

A B Cc D E

Fig. 5.—Sections of date leaves. A, An Areshtileaf. On the L side of the rachis is shown a triple group
of pinnz (a, i, r) and above it a paired group (a,r); on the R side, a paired group (a, r) below and a triple
group (a,i,r) above. B, Section toward the top of a Deglet Beida leaf, view of right side. Below isa
triple group of pinne (a, i, r); above, a quadruple group (a,i,i,r). C, A Deglet Beida leaf, showing on
the left-hand side of the rachis a quintuple group of pinne (a, i,i,i, r). The pulvinus of the antrorse
pinna (a) is caudate, having a tail-like prolongation reaching nearly to the next lower pinna. D, Section
near the apex of an Areshti leaf, in which the pinne are not distinguishable into groups, though Nos. 1,

_ 4, and 7 are slightly retrorse in position. E, A Deglet Beida leaf, showing pulvini of antrorse pinne: a,
a, Caudate; a, i, r; coalescent with the groups above and below by these prolonged pulvini.

divergence from the midrib, or rachis, measured by its angles of

divergence from the imaginary leaf planes. The antrorse pinnx
diverge least from the plane of the rachis, pointing strongly forward,
and their two ranks most nearly approach each other, thus forming
the greatest angle with the plane of the blade. The introrse pinnz
are placed most nearly at right angles with the plane of the rachis,
or rib, and more nearly to the plane of the blade than the antrorse. ~

The retrorse pinne generally point far forward, their divergence

from the plane of the rachis being slightly greater than that of the

12 BULLETIN 223, U. S. DEPARTMENT OF AGRICULTURE.

antrorse pinne. They may lie nearly in the plane of the blade, but
they usually form angles back of that plane which must be measured
dorsally.

_ Toward the base of the blade the groups may irregularly coincide
on opposite sides of the rachis, giving the pinne a tufted appearance

Fig. 6.—Micrometer, reading to 0.001 of an inch,
for determining the comparative thickness of

pinnae of date leaves of different varieties. Fig. 7.—Combination 2-foot rule and protractor with
oe ee vernier for determining the angles at which date-
. : l > : ‘=
and leaving naked spaces of sev- eaf pinnse diverge from the rachis

eral inches between them. In other examples the groups may be
coalescent through the caudate pulvini, or they may be so crowded
that the pinne overlap like the slats in a window blind.

Figure 5, H, shows on the left side of a section a triple group in the
middle, but coalescent with the groups above and below by the
caudate pulvini of the antrorse pinne.

by

an hy

pa.

CHARACTERS OF THE LEAVES OF THE DATE PALM, 13
THICKNESS OF THE PINN4 BLADE.

The pinne in different varieties vary considerably in texture as
well as in actual thickness of the blade. Some are decidedly harsh
to the touch, while those of the other extreme have a smooth, almost
silky feel. Relative differences in thickness of the blades would be
detected by the careful observer by comparison, but by the use of a
machinist’s micrometer this thickness can be made a matter of
record. These instruments are graduated to read to 0.001 of an-
inch or to 0.01 of a millimeter and should have the improved locking
device and safety ratchet for regulating the pressure. (Fig. 6.) —
For uniformity the measurement should be made at about the broad-
est part of the pinna blade and near the middle of one of the folds.
A number of the more familiar varieties have pinne that range from
0.012 of an inch (0.3048 mm.) to 0.020 of an inch (0.5080 mm.) in
thickness. Others are distinguished by the greater thickness of the
blade, as Thoory, with pinne from 0.023 of an inch (0.5842 mm.) to
0.026 of an inch (0.6604 mm.) or more in thickness.

USE OF THE FIELD PROTRACTOR.

For the measurement of the angles formed by the pinnz with the
rachis, or rib, a protractor with rather long arms is essential. As
one of the necessary capacity made with the fine graduations called
for in engineering is both cumbrous .and expensive, a single-jointed,
2-foot metal rule, with 5-degree graduations on the hinge circle ? and
vernier reading to degrees and half degrees on the limb, has been
found to be a very convenient instrument, giving the angles with
sufficient precision and being instantly available for measurements

in feet and inches. (See fig. 7.)
FORMS FOR THE OBSERVER’S USE.

For the field recording of characters the writer has devised a ruled
and printed form, a reduced imprint of which is shown as form A.

1 These instruments are furnished by tool makers in this country for the use of mechanics engaged in fine
work, graduated in fractions ofan inch or decimal equivalents. They may also be obtained by special order
graduated in hundredths ofa millimeter.

2 The hinge cirele is graduated five-eighths of the way around into spaces of 5 degrees each and figured
15°, 30°, 45°, ete., from the zero point at the inner angle when the rule is closed. Any angle a multiple of 5
degrees can accordingly be read with accuracy on this hinge circle, but for the degrees between these marks
the aid of the vernier on the movable arm is needed. As will be seen when this rule is closed, a 45-degree
space on the arm is graduated into 10 parts, so that one of them is equivalent to 4} degrees, or one-half degree
less than the 5-degree spaces on the circle. Every second space or the equivalent 1 degree of difference is
numbered 1 to 5 in order, the 5-line degree coinciding with the 45-degree line on the circle. Now, iftherule
beopened a very little, till the first vernier line marking 4} degrees coincides with the line of the first 5 degrees
on the circle, the arm has moved the difference between these, or one-halfdegree. Open till the second pair
of marks coincides, and twice4s, or 9, degrees of space have been moved to coincide with twice 5, or 10, degrees
on the other side, a movement gaining 1 degree. So we may open to 2°, 3°, 4°, ete. In the same way
starting on any even 5-degree mark, as 45°, we may open one-half degree, 1 degree, 2 degrees more. Hence,
to read any angle that has been taken, read first on the hinge circle to the last full 5-degree mark inside of
the angle, then add to this the degrees or half degrees to the coinciding line on the vernier. In figure 7 the
rule is opened to an angle of 12}°, 10 degrees being read on the hinge circle and 2} degrees on the vernier.

14 BULLETIN 223, U. §. DEPARTMENT OF AGRICULTURE,

The heading provides for entering the tree to be studied, locality,
garden, row and tree numbers, and date, below which the sheet is
ruled in horizontal lines for noting the angles of the different classes
of pinne: A (antrorse), 7 (introrse), R (retrorse). Above the lines,
az indicates that the axial divergences of the pinne—that is, the
angles by which they diverge to the right or left from the rachis—are
to be recorded.

_ Below the lines, p indicates the angles of divergence from the plane
’ that would be formed by a perfectly flat blade. Below these a line
provides for the record of the “ Length of pinne”’ above the line and the
corresponding breadths below, the breadth being noted at the broad-
est part, the pinnez blade being unfolded and spread flat.

Form A.—Date variety, ....-...-- BaP. 4 Non orem sa ee garden...

1 2 3 4 5 6 7 8 +9 10 il 12

PO er ee ee er OE Ss FS es Soe ee ee Se ee ee Eee ees
ne ee a pe re ey eee ee ees ee ee
ee ee ee ee ee ee ee ee ee eee ee

ee ere er ee ee ee ee er ee ee eee Pee eee ete ee re Se pee

The vertical ruling in form A provides spaces for entries for each
foot of blade length from below the first spines to the apex.

For some leaves exceeding a length of 12 feet, the record has to be
carried to the ruled spaces below.

The length of the spine area and the total blade length are indi-
cated at the same time. An average leaf being selected, it is thought
that one or two characteristic readings to each foot of length from base

to apex, usually along one side of the blade only, will record the

characters effectively, and that two or three leaves each from as
many trees will indicate the leaf characters of a given variety. For
varietiés of paramount importance, such as Deglet Noor, Thoory,

Hayany, and a few more, of course a greater number of records are

desirable. \

“Ny lldet nat Si~

a Oa

oly. Paral esa tatiin

CHARACTERS OF THE LEAVES OF THE DATE PALM. 15
GROUP AND CLASS RECORD.

Following the above comes the record of the classes and groups of
pinne, made continuously from base to apex along one side of the
blade. The lower thorns, usually crowded, when not distinguishable
as to class or groups are indicated by a corresponding number of
straight marks, then
the groups are re-
corded by the compo-
nent initial letters
written together; for
instance, ar, ar, ar
would indicate three
successive groups, each
composed of one an-
trorse and one re-
trorse pinna.

ANGLE RECORD OF THE
PINNE.
_ In order to accom-
plish the graphic rep-
resentation of the va-
rious angles formed by
the pinne with the
axis and plane of the
blade, a diagram has
been prepared (form
B)! representing a
semicircular protrac-
tor as it might be ap-
plied for the reading
of the angles recorded
on form A.
_ The first illustration
OF Meese of Lonny Bos oagas Nose dite eas o6 09 et tres ths bse of the Sal,
(fig. 8) shows the pro- recorded on form B. The upper diagram shows the divergence
tractor scale as though pygitioer — sonata i tm
laid flat upon the leaf, ; g BER
the zero line AR drawn through its center being parallel with the
axis of the blade and zero toward the apex, the divergence of the
right and left ranks of pinne would be indicated at 10°, 25°, 45°, ete.
In the second illustration of the use of form B (fig. 9) the protractor
is placed as though cross-sectioning the rachis, the zero line PB coin-
ciding with the plane of the blade and the line of 90° bisecting the

1 Form B, reduced in size, is shown in figures 8, 9, and 10.

° A-R= Aus oF rachis : it i

16 BULLETIN 223, U. S. DEPARTMENT OF AGRICULTURE.

- rachis into two equal parts, right and left. The ventral face of the.

rib is shown at V, the dorsal at D.

It will be noticed that in the illustrations of the use of form B
(figs. 8-10), the protractor circle is carried 20 degrees beyond the
zero plane toward the dorsal face of the rachis. This is for recording
the position of the retrorse — of pinne, which, while sometimes
forming angles of a
few degrees toward
the inner or ventral
side, as a rule lie either
at zero or inclined 5°,
10°, or even 20° dor-
sally.

APPLICATION OF THE
SYSTEM TO _ THE
DEGLET NOOR VA-
RIETY AND ITS
SEEDLINGS.

As the Deglet Noor
is the most prominent
variety of date yet in-
troduced, a more ex-
tensive study of its
foliage characters
has been made than
of any other variety.
The followimg are

_ some of the moststrik-

P=Rachls

= face :
) P-8= Flone of blade

out:

The average of eight ex-
amples of Deglet Noor
leaves gives the spine area
as 35.5 per cent of the blade
Fig. 9.—Diagrams showing the characteristic divergence of the pinne length.

of a Deglet Noor date leaf, at 5 to 6 feet from the base of the leaf, For the same trees theav-
recorded on form B, The upper diagram shows the divergence from rti ‘cai

the blade plane; the lower, the divergence from the apex: A, An- erage prope OD: Oh Pp ne
trorse pinne; J, introrse; R, retrorse. of the different classes, In-

cluding spines where the ~

class is evident, to the total number on the blade, is as follows: Antrorse, 38.1 per
cent; introrse, 19.4 per cent; retrorse, 34.1 per cent; uncertain, 8.4 per cent. The
paired groups of pinne exceed all the othees together.

A larger number of observations of this variety may establish a somewhat different
set of ratios, but these must serve for a working basis till such can be procured.

As showing the application of such study of the leaves of a given
variety and its value in selecting plants for breeding purposes, a com-

ing points peguey

Wp: Shaeadennealeemenetes Sia ages Poe

—-

CHARACTERS OF THE LEAVES OF THE DATE PALM, 17

parison will be made of some of the Deglet Noor seedlings with the
average for that variety, or what may be called a standardized tree.

Two sets of readings were taken from the Deglet Noor fruiting
seedling raised by Mr. James Reed, at Thermal, Cal. In both of
these the data are well within the range of variation of the eight true
Deglet Noor records,
and the average of the
two is curiously near
to the average of the
Deglet Noor. The
pinne are more closely
crowded than in any of
the Deglet Noor rec-
ords, and the percent- =
age of introrse pinnee is
above the average, but
within the range.

The proportion of
paired, triple, and
quadruple groups of
pinne is remarkably
near the average. The
fruit of this presum-
ably half-blood Deglet
Noor seedling has not
been distinguishable
from that of the stand-
ard imported Deglet
Noor varieties. No ° 4=Awa of rachis
other Deglet Noor
seedling has been found
so closely duplicating

the Deglet Noor in
fruit. — Fig. 10.—Diagrams showing the characteristic divergence of the pinn
Of of a Deglet Noor date leaf, at 8 to 9 feet from the base of the leaf,
others that have recorded on form B. The upper diagram shows the divergence from

fruited, showing de-___ the blade plane; the lower, the divergence from the apex: A, An-
cided Deglet Noor a8 oi aed eae tom ana

characters in color, flavor, or texture of the fruit, none has been
found with the same close approximation to Deglet Nose foliage. Ina
slender-fruited seedling, for example, raised by the California Date Co.,
at. Heber, Cal., the fruit has the Deglet Noor flavor and texture in
a high degree. The form of this fruit is long and slender, entirely
distinct from the Deglet Noor. Referring to Table I, showing the
point characters, this variety, as compared with the Deglet Noor,

mI my i
tii
nH

itt

|
i

|
Mtl

18 BULLETIN 223, U. S. DEPARTMENT OF AGRICULTURE.

has the spine area shorter than any of the true Deglet Noor measure-
ments, while the pinne are more crowded and have lower percentages

of antrorse and retrorse pinne and higher percentages of introrse

and undetermined pinne.

There are also a lower percentage of double groups of pinne and
higher percentages of triple and quadruple groups than have been
noted in any true Deglet Noor. On the whole it is considerably out-
side the recorded range of variation for the Deglet Noor variety,
though nearer the type than the average of supposed half bloods.

It seems to be a good working hypothesis that there is a close cor-
relation between the leaf and fruit characters of the date tree. If
this be true, we should look for male trees having the leaf characters
within the range of Deglet Noor variation to give us trees most capa-
ble of transmitting Deglet Noor qualities where used as pollinators.
Failing in this quest, we must use those coming the nearest to such
character.

So far, no male trees have been found among the Deglet Noor

seedlings which correspond to the best Reed seedling in being nearly
true to foliage type. Mr. Reed’s seedling male trees Nos. 1 and 2
are trees of a strong Deglet Noor character, but fall considerably
short of the type. However, they have been used as pollinators, and
many seeds of Deglet Noor fruit of such pollinations have been sown,
but none are old enough to have proved themselves.

TaBLe [.—Comparison of the average wes characters of four important varieties of date

palms.
Degiet
let Noor, |_j. 00”
Average leaf characters. _|Deglet Noor. Reed’s icomned Hayany. | Menakher.| Thoory.
seedling. |“ seed-
ling.
Blade length......... inches. . 126 116 | 110 122 144 126
Spine area:
Barat oo 43 38 24 23 32 32
Percentage of blade length 35.5 33 2 18 22 25.6
Total number of pinne on
one side of rachis..........- 91 98 96 96 122 69
mn:
SOG SE aa 32 35 30 31 27 , 25
Percentage of total....... 35-4 36— | 31+ 324+ 22-4 36+
Eee ES Poa. 20 24 26 19 58 16
Percentage of total 2 244+ |) 27+ 20— Aj — 23+
Retrorse. 2-6 30 32 29 33 35 at
ve remiage of total... 33— 33— | 30+ 34+ = 31—
eri goee eer, 9 7 ll
Pp tage of total... .. os oe wes 1
Number of of pinne: ee os oy = : on
In groups , two... 20 22 1/11 27 12 15
=) ercentage of total... _. €1— 67—| 40,7+ T+ 32+ 60
ae three. 2.2.5 9 7 19 8
ercen of total. 27+ 244 | 29.6 20 52 32
"econ teaver tolie ea 5 : 3 6 3
0! 8
——— of pinne: aed me . =
neheg 5.3855 -- 2 ery 016-0.022 |0.016-0.018 |_....... 0.017-0.020 |0.017-0.022 |0.022-0. 030
Millimeters.....------.-.. - 4064-. 5588 P 4064—. 4727 |... ..... . 4318-. 5080 | . 4318-. 5588 | . 5588-. 7620

eS

ey Ay

ee a

CHARACTERS OF THE LEAVES OF THE DATE PALM. 19

In the analysis of these characters (Table I) the Deglet Noor has
the highest percentage of spine area to total blade length and Hayany
the lowest. Menakher stands out from the group in having nearly
half of its pinne of the introrse class, while Hayany has the lowest
percentage of any in that class. While Deglet Noor, Hayany, and
Thoory have a majority of their pinne groups of the paired class,
Hayany leads in that respect in having but a fraction short of four-
fifths of its pinne groups in the paired class. Menakher, on the other
hand, has a majority of its groups of the triple class.

The descriptions of four date varieties which follow are given as
showing the application of this system of leaf study to the dates in
cultivation. Among the many varieties being tested in the gardens
of the Department of Agriculture these four take first rank in their
respective classes and present such a wide range in leaf characters
as to illustrate very. clearly the principles involved.

DESCRIPTION OF THE DEGLET NOOR VARIETY.

The trees of the Deglet Noor variety have slender trunks and
make a rather rapid height growth, the leaves being 9 to 11 feet
long, erect spreading, forming a rather narrow vase-shaped top,
becoming broader with age. The leaf base is narrow, diminishing to
a firm, gradually tapering rib, which has a slight, graceful flexibility
at the apical portion. Itisstrongly rounded dorsally, well arched ven-
trally, with the lateral faces of more than average breadth (fig. 11).

The spine area averages about 35 per cent of the blade length, the
spines firm, with stout bases, rather long, acuminate, acutely pointed,
crowded below, more scattered in the upper portion of the area, and
decidedly appressed. They pass to narrow spikelike pinne, 12 to 18
inches in length, and the longest pinne, 24 to 27 inches, are reached
at about the middle of the blade while but 1 inch to 14 inches broad.
The greatest breadth of the pinnz, 13 to 14 inches, is usually at
about 6 to 7 feet from the base, where the pinnze are 20 to 24 inches
long. They diminish steadily to 10 or 15, or rarely 18 inches, in
length and seven-eighths of an inch to 1 inch in breadth at the apex
of the leaf. The pinne throughout are acuminate in form and
acutely pointed, varying in thickness of the blade from 0.016 of an
inch (0.4064 mm.) to 0.022 of an inch (0.5588 mm.), from 0.017 of
an inch (0.1318 mm.) to 0.020 of an inch (0.5080 mm. ) being the most
common, the texture being firm and rather harsh than soft. The
blades are closely folded, and toward the apex of the leaf the proxi-
mal fold is slightly wider than the distal and decurrent along the
rachis. The pulvini toward the base of the blade are heavy, some-
times strongly caudate, but the groups are seldom coalescent.

The paired groups of pinne are in the majority, often comprising

60 to 70 per cent of the whole number, while there are about 22 to
30 per cent of the triple groups, and a few are quadruple.

20 BULLETIN 223, U. S. DEPARTMENT OF AGRICULTURE.

- The antrorse pinne comprise from 34 to 42 per cent of the whole
number, the retrorse class furnishing from 31 to 36 per cent, while of

SS 126 0)
4F : cs ()

96 we

2F
. 6 ;
. Cs ots)
oo ee
a c
yt ee

isi ~ | e
E

FiG. 11.—Cross sections of the rachis of a Deglet Noor date leaf, showing outlines at different distances from
base to apex.

the introrse pinne there are but 15 to 25 per cent. Unclassified
basal spines make up the balance.

CHARACTERS OF THE LEAVES OF THE DATE PALM, 21

In divergence from the rachis, the antrorse spines are usually
rather closely appressed, a divergence of only 5° is noted in some,
and other spines may diverge 25° or 30° from the axis. In some
leaves the entire rank of antrorse pinne to the apex may not diverge
more than 25° to 28°, but usually there is a spread through the
middle of the blade of 35° to 42° interspersed with others of only
20° to 23°. In divergence from the plane of the blade, the antrorse
class among the spines shows a good deal of variety, some basal ones
diverging sharply, the majority only from 12° or 15° to 20° to 30°
or more. From the middle of the blade to the apex their divergence
is from 20° to 30° or rarely 40°, 45°, or more.

The introrse class, seldom found among the spines in this variety,
shows strong axial angles of 40° to 50° and up to 72°, while from the

_ blade plane their divergence ranges from zero to 15°, 20°, or 25°, a
_ few forming angles of 35°, 40°, or even more.

Tn the retrorse class a few spines may stand out strongly from the
rachis, but the majority are rather appressed. The retrorse pinne
as a rule spread more than do the antrorse class at the same distances
out on the blade, ranging from 24° to 40°, 45°, or 48°.

Measured from the blade plane this class has a distinct position,
some being placed at zero or at 5° ventrally, but the great number

incline backward from the plane, forming dorsal angles of 5° or 10°.

For a comparison of Deglet Noor seedlings of various grades with
the pure variety, the above percentages and records of angles will be
found to afford the means for making very close distinctions. This
is important, from the fact that thus far comparisons seem to show
a strong correlation between leaf and fruit characters, the seedlings
bearing the nearest typical Deglet Noor fruit showing Deglet Noor
leaf characters in greatest detail. By analogy, it is presumed that
there will be a similar correlation between the leaf characters of male
seedling trees of a given variety and their capacity for transmitting
the characters of that variety when used as pollinators.

Putting the above dry array of figures into concrete form shows
that the Deglet Noor has a suit of leaves thoroughly well armed at
all angles of approach, especially the lower portion of the blade, with
acute spines and sharply tipped pinnew. The protection of the tender
emerging leaves, but especially of the emerging flower stalks, is well
provided for. In cultural practice the operator in our country is
accustomed to clip off with stout shears the most of the spines, in order
to give him access to the flower heads for pollination.

The fruiting stalks, or sobata, of the Deglet Noor are one of its
most characteristic features. (Fig. 12.) They are, with the strands,
or shamrokh, which bear the fruit, pale lemon colored in contrast with
the orange-yellow or orange aisles of most varieties. They are un-

22 BULLETIN 223, U. S, DEPARTMENT OF AGRICULTURE,

usually long, from 3 up to 4 or 5 feet, and 1} to 14 inches broad on
mature trees. The fruiting head, or portion bearing the strands, is
short, the strands numerous, often 18 to 24 inches, or occasionally
27 to 30 inches long, sometimes forked. The proximal naked
portion.of the strand (one-third to one-half of the length) is sharply
and irregularly quadrangular in cross section, the fruiting por-
tion irregularly oval, with short zigzag angles. From 20 to 30
fruits are sometimes set on a single strand. With the growth of

SS \\\

NEY

aie
A’
Ke
vO)
S\
“i

=
ys A
Cae ces a
ee
QE
iW

me

Y

& PX
Sts

yt) ay,

NG, =
YAS
susie
AY 1 A

ral Qa
DISISS

¢ Ce

19,
0
SDs
ca

SAY
as
fat
ws we
ei
SARS
SAU
Pieene
CY nA YW.
LY a KN
LST cho C4
TING AREA

A AN

'
“A
'
'
1
1

FRU

av8)

Fig, 12.—A bunch of dates of the Deglet Noor variety, showing the fruit
stalk, or sobata; the fruiting head, or portion on which the strands are
borne; and the strands, or shamrokh, comprising the clear.area and the
fruiting area.

the fruit in weight,
the stalk curves
downward, till the
entire load often

hangs suspended ~

nearly vertically.

DESCRIPTION OF THE
HAYANY VARIETY.

(Birket el Haggi, Birket el
Hajji, Birket el Hadji.)

The trees of the
Hayany variety
have rather slender
trunks and mod-
erate outcurve of
leaves, forming a
broadly vase-
shaped top.

The leaf bases are
rather coarse,

broadly wedge

shaped, narrowing
abruptly to a

wedge-shaped petiole. The rachis is of medium size, well rounded
dorsally, and the lateral faces rather broad, the size diminish-
ing gradually, but there is a decided grace and flexibility toward

* Several trees of this variety were received by the Office of Foreign Seed and Plant Introduction under
the name of “Birket el Haggi” from Mr. Em. C, Zervudachi, of Alexandria, Egypt, in 1901, and listed
under S. P. I. No. 7635. Upon fruiting they proved to be identical with “Hayany,” S. P. I. No. 6438,
secured by Mr. Fairchild earlier in the same year. Hayany is the correct name of the variety, which is
the most numerous and most popular date of Lower Egypt. The name “Birket el Haggi” is only men-
tioned among Egyptian dates by Delchevalerie, who erroneously mistook the locality designation for the

real name of the variety. : :

On the writer’s visit to the Birket el Hagg district in September, 1913, he found that the people knew of
no date named “ Birket el Haggi,” but that they had thousands of ““Hayany”’ trees, the fruit of which was
among the earliest to reach the Cairo and Alexandria markets, and so tock the locality name, as ““Chau-
tauqua grapes” or “ Riverside oranges” do in our country. Popenoe, ‘‘ Date Growing in the Old and New
World,” adopts the form “Birket el Hajji,” in conformity with classic Arabic pronunciation, though
“ Birket el Hagg”’ is the correct transliteration of the name of the pool and village accepted by all Egyp-

tians and is on most of their maps.

a

CHARACTERS OF THE LEAVES OF THE DATE PALM. 23
the apex of the leaf (fig. 13). The spine area is unusually short,
about 18 to 25 per cent of the blade length, and the spines are
rather long, slender and acute;
where considerably shadéd Ra fe:
they are inclined to be weak ¢
and soft. The spines merge
into narrow spike pinne, fol-
lowed by ribbon pinne 24 to
30 inches long and one-half to JOB

five-eighths of an inch wide,
which are frequently pendu-
lous, but soon give place

through the middle of the re
blade to those of normal form, 96
18 to 24 inches long and 1 inch

to 1} inches up to 14 or 2

inches wide with narrow at-

tenuate tips, gradually dimin- a
ishing to about 10 or 12 inches i,

long at the apex. The pulvini
are but moderately developed
and creamy in color.
The lower 10 or 15 pinne on
either side have a solid neck, :
which will be called the collum, 4S

from one-half inch to 2 inches

in length, just above the pul-

vinus, from which the pinne

expand into the folded blade of

normal form. These are most 24
strongly developed on the re-
trorse class of pinne. This
character, while slightly devel-

oped in a few other Egyptian

varieties, is almost an identi-

fying character for this variety.

The pinne blades are smooth

and rathersoft, notrigidly acute

at the apex, but inclined tosplit S4A5E

up. The axial divergence Of Fig. 13.—Cross sections of the rachis of a Hayany date
the pinne is, for the antrorse rag ee at different distances from base
class, only about 20° to 35°

near the base, becoming 45° or 50° toward the apex. The introrse
and retrorse classes diverge more strongly, in some leaves to 60° or
65°. In divergence from the plane of the blade the antrorse pinne

24 BULLETIN 223, U. 8S. DEPARTMENT OF AGRICULTURE.

form ranks which diverge 30° or 40° to 55° or 60°, while the introrse
and retrorse pinne lie within 10° of the planes or diverge a little
dorsally.

At Tempe, in a heavy adobe soil with an excess of subterranean

moisture, this variety has been prolific in offshoots and sets them well

up on the trunk, one

tree as early as 1909

() having six offshoots

< at a height of 4 to 44
feet.

The fruit stalks are

orange yellow, about

O) 24 or 3 feet long, 1?

132 to 2 inches broad, the

fruit head compact
and heavy, and the

strands, or shamrokh,
48" 1 of medium length and
420

143

rather coarse.

DESCRIPTION OF THE
MENAKHER VARIETY.
The trees of the

Menakher variety are

of beautiful and strik-

ing appearance. The

growth is vigorous,

though not as rank as
- some other varieties,
and the height growth
of the trunk has been
rather slow.

The foliage is a dark
rich green, with abun-
‘dant glaucous bloom.
The leaves are 9 to 12
feet long, curving out-
ward rather stiffly
below, but with an in-
creasing flexibility to-

wt

Fic. 14 —Cross sections of the rachis of a Menakher date leaf, showing .
outlines at different distances from base to apex. ward the apex, which

gives along and beau-
tifulsweep. The leaf bases are 7 to 9 inches broad, heavy, narrowing
gradually to a stout, strongly rounded rib, which tapers Te toa
moderately slender apex (fig. 14).

PLATE V.

Bul. 223, U. S. Dept. of Agriculture.

Four SECTIONS OF A MENAKHER DATE LEAF. (NEARLY NATURAL SIZE.)

Fig. 1.—A leaf section near the base, showing a paired group, a, r, of very acute spines.
Fic. 2.—A section at 8 feet, showing a quadruple group, a, i, 7, r, below and a triple group,
a,i,r,above. Fias. 3 and 4.—Sections at 10 and 12 feet. showing some well-defined retrorse
pinne, r, r. The others will class as introrse, and no regular groups can be determined.

CHARACTERS OF THE LEAVES OF THE DATE PALM, 25

‘The spine area is s from 20 to 25 per cent or more, rarely 33 to 36 per
cent of the blade length. The closely set spines are short or of medium
length, strong, but acute, closely appressed, passing to narrow spike
pinns 20 to 24 inches long: The regular pinne at 5 to 6 feet from the
leaf base are 17 to 24 inches long, 1} to 1? inches broad, decreasing
in length rather gradually to about 9 to 12 inches long at the apex.
(PE

The pinne blades are 0.017 of an inch (0.4318 mm.) to 0.022 of an
inch (0.5588 mm.) thick, firm in texture but not harsh, broadest near
the base, tapering evenly to a rather acuminate acute apex. In the
upper portion of the leaf the proximal fold of the pinnx blade is decid-
edly broader than the distal, decurrent along the rachis, but the prom-
inence of the ventral arch of the rachis leaves the channel formed by
opposite wing margins rather open until near the top of the blade.

The pulvini are moderately heavy, frequently slenderly caudate,
and there are many coalescent groups in the lower portion of the blade.
The paired groups of pinne are considerably outnumbered by the
- triple and quadruple groups. The introrse pinne usually comprise
from 40 to 48 per cent of the entire number on the blade, but some-
times yield to a high number of the retrorse class.

The slight axial divergence of all classes of pinnx and the rather
even and moderate divergence from the blade plane give to this
variety a smooth, even leaf, which, with its dark, rich color, is very
attractive.

The antrorse spines have but 10° to 15° of axial divergence, the
lower antrorse pinne 15° to 20°, spreading to 30° toward the tip of ~
the leaf.

The antrorse pinne diverge axially about 45° through the middle
of the blade and 30° at the apex. Both these classes form angles with
the blade plane of 20° to 30° or 36° in the outer 2 feet.

The axial angles of the retrorse pinne are a little greater than in the
first-named classes, the lower pinne 20° to 28° or 30°, the rest of the
blade 30°. These spines diverge about 15° deriaily. the pinne 5°
dorsally, or all the upper portion at zero. In a few instances the
retrorse spines and lower pinne have a dorsal divergence of 30° to 33°.

The fruit stalks are heavy, 3 to 4 feet long, the fruiting head 12 to
15 inches long, with numerous strong strands 12 to 18 inches in
length, making a heavy, compact bunch of fruit.

But two genuine trees of the Menakher variety were finally pre-
served of the importation made by Mr. T. H. Kearney in 1905. One _
of these is at the Cooperative Date Garden at Tempe, Ariz. The —
other is at Mecca, Cal. The Tempe tree has made the slower growth,
though it is a healthy and vigorous-looking tree. In November, 1912,
its terminal bud was only 3 feet from the ground, while that of the
Mecca tree was 7 feet high, with a trunk diameter of 2 feet. Whether

—- 26 BULLETIN 223, U. S. DEPARTMENT OF AGRICULTURE.

the greater heat at Mecca or the difference in the soil is the cause of
this difference in growth is not easy to say. The Tempe garden is
located in a strip of land having a heavy adobe soil and so high a
percentage of alkali that ordinary grain and forage crops can not be
grown upon it. By the underflow of ground water from irrigated
districts above, the water table has not been below 4 feet for a number
of years and stands near the surface in the winter months.

The conditions at the Mecca garden are in strongest contrast with
these. ‘The soil is a fine sand, the bed of the old Salton fresh-water
lake, having a considerable percentage of calcareous material in the
form of partially decayed small fresh-water shells, and underlain
with a few shallow strata of blue clay or silt. The only organic matter
has been supplied by cover crops and the liberal application of stable
manure around the roots of individual trees.

There is but a slight trace of alkali, and irrigation with very pure
water from an artesian well has been abundant. While too positive
conclusions should not be drawn from the behavior of a single tree in

-each locality, a similar slowness of growth has been noted in several -

trees of Thoory at Tempe, as contrasted with a very vigorous and
rapid growth of that variety at Mecca and Indio. At the same time a
number of varieties, such as Deglet Noor, Rhars, Itima, and Tadala,
under Tempe conditions have made a rather better growth than in the
sandy soil and greater heat of Mecca.

The presumption is strong that the Menather variety finds both the
temperature and the sandy soil, with the absence of the alkali of the
Mecca garden, the more congenial. In fruiting, both trees have been
slow to develop fruit of normal quality, but have improved from year

to year. At Tempe, however, it hardly seems likely that this variety

has heat enough to perfect its fruit. While a good crop was set in
1912, it was found still immature on November 10. Some fruits were
coloring properly on one side and had ripened a portion of the flesh,
which was of excellent flavor, but the most of them were tough
and ‘‘cottony,” and a good sample box could not have been collected.
At Mecca a good deal of fruit developed sufficiently to be finished by
‘“‘slow maturation”’ into a very excellent product. The rarity of this
variety in Tunis and the consequent scarcity of offshoots that may be
purchased will probably prevent its assuming commercial importance
in the Salton Basin for many years to come.

Yet, considering the past year’s performance of the Mecca tree,
the writer feels that the Menakher should be regarded as promising
to become one of the great commercial dates of the Salton Basin
when it can be propagated in sufficient numbers.

DESCRIPTION OF THE THOORY VARIETY.

The trees of the Thoory variety are of very robust growth, with
short heavy trunks. The long, heavy, rather yellowish green leaves

lia oie! Maal

CHARACTERS OF THE LEAVES OF THE DATE PALM, 27

are stiffly erect or spreading in an angular manner by bending near
the base. The leaf bases are 5 to 8 inches broad, diminishing gradually

Fig. 15.—Cross sections of the rachis of a Thoory date leaf, showing outlines at different distances from base os
to apex.

to a broad, heavy rib, which tapers but slowly to the apex, where
there is a slight flexibility (fig. 15).

28 BULLETIN 223, U. 8S. DEPARTMENT OF AGRICULTURE.

The spine area is short, 15 to 30 per cent of the blade length, the
sparsely set spines rather short, slender, acute, passing to a few stout
spike pinnez, 18 to 21 inches or, rarely, 25 inches long at 3 to 5 feet
from the base. These are followed by pinne 18 to 23 inches long,
diminishing slowly toward the apex, still 15 to 18 inches long at 8 or
9 feet, and the last apical ones dropping to 12 or 13 inches.

The pinne blades are coarse, harsh, and acute, 14 to 2 inches broad
through the greater portion of the leaf and 14 to 14 inches at the apex.
They are 0.018 of an inch (0.4572 mm.) to 0.024 of an inch (0.6096
mm.), occasionally 0.030 of an inch (0.7620 mm.) in thickness. The
pulvini are heavy, often short caudate, and coalescent groups are
common. The average space for each pinna on the rachis is broad
(1.64 inches to 2.18 inches are recorded); the spines are close together
at the base, but wide apart above, while the pinne range from 2 inches
apart in the middle of the blade to 1} inches, or as close as 1 inch in
the apical portions, but from their unusual breadth and small angles
of divergence they appear crowded and overlapping. —

The paired groups of pinne are in a decided majority, the triple
groups average about half as many, and there are a few quadruple
groups. The antrorse pinne diverge from the rachis by rather
slight angles, the basal spines 25° or 30°, those above but 5° to 15°,
the pinne from 10° to 12°, 15°, or 19°, with a small number at 25° to
32°. They form blade-plane angles of 10° to 15° for some of the
spines and lower pinne to 22°, 25°, 32°, to 39° and 40° at 6 to 9 feet,
with 30° to 35° near the apex.

An examination of leaves with the stiff, acute, antrorse pinne placed
at these angles will convince one that their defensive efficiency is
about perfect.

The introrse pinne, relatively of minor importance in this variety,
have an axial divergence of 40° to 72°, some of them being at
zero with the blade plane, others diverging 10°, 20°, to 30°, or 63°.
The retrorse pinne diverge from the rachis from 25° or 30° through
35° and 48° to afew at 55° or 57°. These angles, combined with their
dorsal divergence of 5° to 10° from the blade plane, give these two
rather ragged ranks a very effective position for defense.

The fruit stalks are strong, 14 to 2 inches in diameter and 2 to 4
feet long; the strands are coarse, 12 to 24 inches long; the color a
bright orange.

The fruit of this variety, which affords one of the best examples of
the dry-date class, is produced in heavy crops, the few trees in bearing
showing a tendency to bear in alternate years.