_U.S. DEPARTMENT OF AGRICULTURE,
~ BUREAU OF PLANT INDUSTRY-BULLETIN NO. 102, PART I.

. Le a g ‘ ; ie TY. GALLOWAY. Chiof of Bureau. ee

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SUMMARY OF RECENT INVESTIGATIONS -
OF THE VALUE OP CACTI 38
AS STOCK FOOD, a.

DAVID GRIFFITHS,
Assistant Agrosronocisr, Farm MANAGEMENT INVESTIGATIONS,
BUREAU OF: PLANT PDE Srey; :

RF. PARE,

| CHEMIST, New Mexico CoLLEGE or Acricunture AND
Mercuanic Ape soos

Issupp January 4, 1907.

WASHINGTON:
GOVERNMENT PRINTING OFFICE,
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BUREAU OF PLANT INDUSTRY—BULLETIN NO. 102, PART I.

B. T. GALLOWAY, Chief of Bureau.

SUMMARY OP RECENT INVESTIGATIONS
OF THE VALUE OF CACTI
AS STOCK FOOD.

BY

DAVID GRIFFITHS,

ASSISTANT AGROSTOLOGIST, FARM MANAGEMENT INVESTIGATIONS,
Bureau oF Piant INpDustTrRY,

AND
R. F. HARE,

Cuemist, New Mexico CoLLeGr oF AGRICULTURE AND
Mecuanic Arts.

IssureD JANUARY 4, 1907.

WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1907.

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ILI GROG HOCMOSD oo Aa Aas Ree NS se ae RES eT ne Ry en EN Sree a a a
sinersaunplestotcacti analy. Zed “tan: sheesh ane eee yet aN ee ea
RNPICCTRCOMUCTNGNE th yee Braet <1) irene rep ih Geeta en We eS Seg tens
PASIIMCOM LCI beget y ree sarge shal gen i Sosy anay aie mip Cm aS Sa AE Sas
Hoodavaluekoiditterent parts ofthe: plamts2.092---425 522-50 -020-5-- 5-2 5-25:
ebalancederationyol prickly pear. ws oie feet PT ee eo aan
elaine value on thesthree erotps of Cachle se s-425 5925 ee. 5- ees
Cormmmongancdkscreutuic-mamess + alee ele se oes ee oe ease) Set eee
Chinatiexequmementsiot prickly pearss.2 4-4. 9262524242252 52-2 oes s eee :
dinemuserotspriclslyaear im Mexi@O 427855 e eee Se a oe
where ctesoiscactiand them analysesso: 2-2-0028. 522 s-seb - esc cee-

PE STO Ne

Puatst I. Nopal cardon (Opuntia streptacantha Lehm.), the most important of
the Mexacanpricklyspearsie--er -e-seeee = ee Fate earch Seatac e e

102—I

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B. P. I.—242.

SUMMARY OF RECENT INVESTIGATIONS OF THE
Pon CACIEAS STOCK FOOD:

INTRODUCTION. .

In connection with introductions, the improvement of species, and
a general study of the economic relationships of native and intro-
duced species of cacti the authors have jointly undertaken a somewhat
critical comparison of the species of this group from a forage stand-
point. In order to make the chemical work worth while it has been
necessary to put the characterizations of the different forms and
species in such condition that they are recognizable to others. This
could only be done by the use of copious notes in connection with
each, for names are of uncertain meaning and in many cases will be
of uncertain significance in this group of plants for a long time to
come. The chemical side of the investigations seems to be essential,
for when these studies were begun there was but little literature deal-
ing with the cacti from a forage standpoint.

aIn two publications of the United States Department of Agriculture (Bulletin
No. 74 of the Bureau of Plant Industry and Bulletin No. 91 of the Bureau of Animal
Industry) the value of the cacti as forage plants has been demonstrated. Since these
plants are known to possess important economic value more knowledge concerning
them is desirable. As a basis for future investigations, the Bureau of Plant Industry
and the Agricultural Experiment Station of New Mexico have collected specimens of
these plants and their fruits from a wide area, from which a large number of chemical
analyses have been made. The results are detailed in the following pages, which
contain 187 fodder analyses and 26 complete ash analyses. The territory from which
the material was collected extends from central Texas to California and southward to |
the central plateau of Mexico.

Attention is called to the fact that the apparent high content of fats and protein in
the fruit of certain species is due to the large amount of these classes of nutrients found
in the seed. As these seeds are surrounded by a dense layer of wholly indigestible
tissue, the high content of ether extract and protein is misleading. The analyses
show that the fodder value of the fruit of cholla (Opuntia fulgida) especially is little
more than that of the stems. It will be seen that in chemical composition the different
forms of cactus compare favorably with ordinary green fodders and root crops.

There are many points of special interest in connection with the ash analyses, par-
ticularly the high content of potash, magnesium, and calcium. Altho the cane cacti
_ show a relatively higher food value, practical considerations relating to growth and
ease of propagation render them of less value than the prickly pear, except in certain
limited localities where they are especially abundant.—W. J. Sprnuman, Agriculturist
in Charge of Farm Management Investigations.

102—I

6 VALUE OF CACTI AS FOOD FOR STOCK.

The investigations have been conducted in cooperation between
the Office of Farm Management Investigations of the Bureau of Plant
Industry and the Agricultural Experiment Station of New Mexico
for the purpose of determining, if possible, the extent of variation and
the nature of the food constituents of the different species which are
likely to be utilized as food for stock. The plants are grouped under
three general headings—prickly pears, cane cacti, and miscellaneous—
the first group being by far the most important, tho the second is
largely utilized in sections where its different representatives grow.
Three or four members of this group have been fed to stock with |
more or less success. The third group consists of miscellaneous ~
species from other cactus genera, which on the whole are but little
utilized as stock feed, altho it is clearly shown that some of the species
have been fed in rare instances. The interest in this group is largely
a matter of comparison with the others. . ;

Details of the investigations are published in Bulletin No. 60 of
the Agricultural Experiment Station of New Mexico.

THE SAMPLES OF CACTI ANALYZED.

Considerable importance is attached to the method of sampling,
it being recognized that uniform samples of such succulent and vari-
able plants are difficult to secure. It appeared more logical, there-
fore, to describe the samples in such a way as to give other investi-
gators and the reader an accurate idea of the portion of the plant used
in the chemical analysis. The sample is indicated by a formula—
for example (2—1—-4—3-5) 3—in which the left-hand figure indicates
the number of terminal joints, the second number from the left the
number of joints next to the terminal joint, and so on, the figure
outside of the parentheses indicating the number of plants from
which the sample was collected. All samples were forwarded to
the laboratory in tin cans from which a minimum of evaporation
took place. They were prepared by first being sliced open, so as to
expose a maximum of cut surface, and dried by artificial heat at a
temperature of not more than 70° C. The spines were then singed
off by a small flame of complete combustion, care being taken neither
to deposit combustion products upon nor injure the specimens. In
the analyses the methods of the Association of Official Agricultural
Chemists were followed, with the exception of a few modifications
in the determination of certain ash constituents.

WATER CONTENT.

A collection of samples for chemical analysis was begun in 1904,
and a fairly complete set was secured during that year; but, owing
to the uncertainty due to the analysis of single samples, these were
nearly all duplicated in 1905, in most cases from the same localities.

102-1

ASH CONTENT. 7
Fortunately there was a great difference between the rainfall during
the months from January to March of 1904 and 1905. The effect
upon the water content of the plants is fairly well illustrated in the
different tables of analyses, altho no special effort was made to collect
the samples for the purpose of showing this feature in detail. There
are some apparent exceptions to the rule that the samples collected
In 1904 contain more water than those collected in 1905; but this
may be accounted for in some cases by the difference in the portions
of plant collected or in other cases possibly by local conditions.
The amount of water in the different samples analyzed varied from
60.99 to 95.5 per cent. The miscellaneous group is relatively more
succulent than either of the other two, the average amount of water
being 87.88 per cent, while the prickly pears averaged 84.26 per cent
and the cane cacti 78.47 per cent. As a rule, the fruit contained
more water than the stems and the younger growth more than the
older.

The difference in the species in the field during a dry and a wet
season is very marked, and even prickly pear has its limit of drought
endurance. Experience in southern Texas demonstrates that it is
much reduced in value during very prolonged dry seasons, for it
becomes tough and leathery. ‘‘Fat pear”’ is largely the result of
distention of the tissues by water. Some species, Opuntia fulgida
especially, when a favorable moist season follows an exceptionally
dry one, will absorb so much water that the fruits and young joints
become ruptured by the excessive turgidity, and this often occurs
with the fruit of nopal camueso and other cultivated Mexican species.

ASH CONTENT.

Plants grown in the arid and semiarid Southwest, where there is an
abundance of soluble salts in the soil, are found to contain more ash
than those grown in regions of frequent rainfall. The cacti are cer-
tainly no exceptions to this rule. The average ash in the air-dried
stems and fruits of the prickly pears analyzed amounts to 18.25 per
cent, for the cane cacti 15.50 per cent, and for the miscellaneous group
13.54 per cent, one sample running as high in ash as 33.8 per cent of
the air-dried substance. These averages would be still higher if they
did not include the ash of fruits, which always contain less ash than
the stems. The average ash in the air-dried fruits of the prickly
pears, for instance, is 13.21 per cent, which is 5.4 per cent less than is
contained in an average of both stems and fruits of this group and 6.35
per cent less than is in the stems alone. It is the seed which is espe-
cially low in ash, the fleshy portion resembling the stem more closely
so far as its ash content is concerned. This is brought out very
forcibly in samples Nos. 8022a and 80226, the former being the fleshy

102—I

8 VALUE OF CAOTI AS FOOD FOR STOCK.

portion and the latter the seed of Opuntia phaeacantha. The fleshy
portion contained 25.60 per cent of ash, while the seed contained only
1.77 per cent.

The elements of the ash are present in about the same proportion as
in the ash of other plants, except potassium, magnesium, and calcium,
which are found in large amounts. It is probably the presence of
these salts, coupled with the high water content, that causes cattle to
scour when fed on an exclusive roughage ration of these plants.

In the following table there is given a complete analysis of the ash
of a few of the samples, together with the results of the analysis of a
composite sample, and an average of all the ash analyses made. Com-
plete ash analyses were made of 26 samples besides the composite,
which was a mixture prepared by carefully icniting in a muffle two
grams of the ash of each of the 187 samples of cactus analyzed.

TaBLe I.—Chemical analyses of representative samples of cactt.

2 hols
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2 Scientific name of cactus. Locality. Callea Horn. S) Aus
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6255 | Opuntia fulgida .............-. Santa Catalina | May 4,1904| (6-6) | 14.25| .74| 1.65
Mountains, Ariz.| :
6331 | Echinocereus enneacanthus ...| Eagle Pass, Tex..; May 10,1904) Plant...| 17.78 | .26 | 3.31

3000 | Opuntia macrocentra.-.-.--.---- Garfield, N. Mex..) July 11,1904 62 | 4.27
6699 | Cereus gigamteus -.--.........- MacsonAtrizesees | July 28,1904 17 | .44
7515 | Opuntia lindheimeri........... Encinal, Tex...-. Jan. 17,1905 ~ 14) | 229
COTM POSTER eee ee Spec SP St aN ee TE .38 | 3.17
Average ofall ashes.) oon sae ee Ee EE ee eee } . 40 | 2. 40
Pure ash.
2 6 y
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4 a S 2b S a a | Ae Se Bs os
2 | Scientific name of aloeealaes SAN Gleason a) a cs
iS cactus. ots hy g q Sls |S | oS! S a
| ® 5 iS p r= S a SA) on |] S23 2 on
3 See ee) Se ie |e les es | gee
(2) Vw S b0 35 Ss n 3 os or =| act Or feels
a gs is i ei) Ss ay |S a TeOl Sess | asi & |es) =
5 Sele lh ec l on les tees erste zl yy BS | oS
4 oebiashd) cst Oe ere eae aoe D 2 |S a
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P.ct.|P.ct.|P.ct,|P. ct. |P.ct.| P. et.) ©. ct.) P. ct.) P. ct.|| P. ct. |P. ct. | Ps ch | Prete
6255 Opuntia fulgida ../0.21 |0.53 |0.09 (24.31 10 11.89 | 0.00 | 0.63 | 2.54 | 2.00 | 1.33 |42.73 | 94. 36

. 07 16.61 | .62) .80 42.63 | 95. 37

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6331 | Echinocereus en- | .31 | .13 | .09 |22. 66 |5.
| _neacanthus.
3000 | Opuntia macro- | .53 | .00 | .56 |24.75 |8.25 | 8.33 | 1.57 | 1.56 | 2.14 | 1.16 .95 |44. 80 | 94.60
centra.
6699 | Cereus giganteus..| .30 | .07 | .15 |31.64 |5.78 | 6.66 | .00) .37/] .88| 4.12 | 3.32 |41.06 | 94.55
7515 Opuntia lindhei- | .20 | .00 | . 49 |26.71 |2.27 |14. 22 39] .43 | 1.11 | 1.15 | 2.15 |49.12 | 98.26
(epernole nic
Composite..| .36 | .31 | .83 |28.90 |6.85 |10.49 | .47 | 1.90 | 2.70 | 1.94 | 2.20 |33.76 | 90.71
se Neteee of | .31 | .24] .36 |27. 38 |5.31 | 9.71 42 | 1.58 | 1.39 | 1.64 | 1.84 45.90 | 95.75
all ashes. |

coy a For explanation of formula, see page 6.

VALUE OF DIFFERENT PARTS OF PLANT AS FOOD. 9

FOOD VALUE OF DIFFERENT PARTS OF THE PLANT.

The opinion is prevalent in southern Texas that the old woody
stems of Opuntia lindheimert fed there are much more valuable as a
stock food than the younger growths. So firmly do many believe
this that they practise cutting off and throwing away two or three of
the terminal joints when feeding. In Mexico, on the contrary, the
young growth is always fed; but there the species are commonly
much larger and stouter, and the trunks are altogether too woody
to be fed even if it were desirable to do so. The reasons for the opin-
ions current in Texas are rather clearly brought out in the analyses.
The younger growth has a relatively higher water content, and there-
fore probably causes more scouring, which is the only evil influence
overcome by a rejection of it. On the other hand, the old stems
- contain a much larger proportion of fiber and are really of less forage
value.

Guthrie,“ after comparing his own analysis of the stems of four
Australian species with the analysis of fruits made by Wolf, concludes
that the latter are of less forage value than the stems, because they
contain a smaller proportion of nutritious substance and more crude
fiber. Forbes,® on the other hand, concludes from analyses of Ari-
zona cylindrical-jointed species that the fruits of these species are
relished by cattle on account of their high ether extract (including
fats). Our analyses show that the ether extract is mainly a constit-
uent of the seeds, and since these pass thru cattle undigested can
contribute nothing to either the palatability or nutritive value of
this part of the plant. That the seed is not digested is plainly shown
in the case of Opuntia lindhewmert in many favorable seasons in por-
tions of Texas. In the vicinity of Austin, in the early spring of 1904,
there were numberless young plants springing up from cattle drop-
pings in many of the pastures. They were fully as numerous in some
situations as are the seedlings of the mesquite under similar condi-
tions in favorable seasons in the river valleys of Arizona and on the
plains of southern Texas.

This applies to the genus Opuntia, to which belong the prickly
pears and cane cacti. The seeds of the other group are very different
in character. There is no doubt that burros, which commonly feed
upon the fruits of the viznaga (Hchinocactus wislizent), get a great deal
of nourishment out of the seeds, which are very oily and easily masti-
cated. It is interesting to note that No. 8170a (Opuntia fulqida)
contains but little more food value in the whole fruit than is found
in the pulpy portion alone, but in this sample most of the seeds were
poorly developed or sterile. Other samples of fruit of the same
species show an apparently greater food value.

a Acricultural Gazette, New South Wales, 11: 671. 1900.
6 Arizona Agricultural Experiment Station, Annual Report, 15: 496. 1904.

102—I

10 VALUE OF CACTI AS FOOD FOR STOCK.

Taste I1.—Chemical composition of the different parts of fruits of cactr.

aS af Nitro- Or-
Scientific name of Part of fruit , ro- gen, F ganic
Be: cactus. analyzed. Water. |; “Ash: | tein. Fat. freeex- Nee mat-
| tract. ter.
ple. |
| Pict. | P. ct. | -P. cbs || Pct. | Beet.) ech Paae
8022a | Opuntia pbaeacantha| Seed........-- 7. 26 io) 6/07) 1154 | 23718550233 90. 99
8022b | Opuntia phaeacantha|) Pulp........-- 92. 50 2.09 | . 20 - 07 4.63 ~ol 5. 41
8162a | Opuntia spinosior ..-| Whole fruit..:| 77.74 2.97| 1.74 1.12 | 11.50 4.94 19. 29
8162b | Opuntia spinosior...| Pulp.-........- 83. 04 3. 10 | 51)5) 24] 11.74 1. 33 13. 86
8173a | Echinocactus wisliz- | Seed.........- 8. 59 3.09 | 10.92 | 15.46) 36.59] 25.37 88. 31
eni.
8173b | Echinocactus wisliz- | Pulp....------ 94.14 96 | 63 06 3.05 1.16 | 4.90
eni.
8170a | Opuntia fulgida...__- Whole fruit...| 82.84 2.70 - 63 etoil |) ill a) 1.69 14. 46
8170b | Opuntia fulgida..---- JPN eseaceas 87.17 1.58 47 om 9. 66 91 11. 25

It must be undertood that we have analyzed here but few fruits
aside from those which are of more value for forage than they are as
food for man. None of the cylindrical-jointed species and but few
of the native prickly pears of the United States bear edible fruits.

A BALANCED RATION OF PRICKLY PEAR.

To determine in just what proportion cactus should be fed with
other foods to produce a balanced ration, it is necessary to know the
amount of digestible nutrients contained in the cactus, as well as
those of the food or foods with which it is to be fed. This has been
determined for most foods, but unfortunately there are as yet no such
data for the cacti. It is hoped to be able soon to obtain the coeffi-
cient of digestion for Opuntia lindheimert. For the present, all that
can be done is to assume this digestibility coefficient to be the same as
that of some food as similar in chemical composition and properties to
the cacti as possible. It is somewhat difficult to secure a green fodder
very similar in character to cactus, but perhaps its digestion coeffi-
cient will not be mist very far by assuming it to be the same as that of
immature green corn fodder. By using the coefficient for this fodder
the nutrients in Opuntia indheimer are found to be: Protein, 0.47 per
cent; fat, 0.26 per cent; carbohydrates, 7.85 per cent. This being the
case, cactus would have a nutritive ratio of 1:18, a ratio which
according to the best authorities would prohibit its use alone for any
feeding standard. The nutritive ratio for a standard ration varies
from 1:4 to 1:12, depending upon the age, character, and kind of
animal to be fed, as well as the object of the feeding; that is, whether
it is desired to produce work, flesh, or milk.

If the object of feeding is to produce milk, a cow giving a heavy
yield of milk should, according to the best authorities, be fed about
25 to 30 pounds a day of organic matter, containing from 1.8 to 2
pounds of digestible protein, from 0.4 to 0.7 pound of digestible fat,
and 11 to 13 pounds of digestible carbohydrates, making a nutritive

102—I

A BALANCED RATION OF PRICKLY PEAR. il

ratio of from about 1:5.5 to 1:7. If a cow requiring a ration of this
kind should eat cactus alone, it would take 160 pounds to furnish the
fats and carbohydrates and an additional 240 pounds to furnish
sufficient protein, and since to avoid scouring a cow should prob-
ably not be fed to exceed 50 or 60 pounds of cactus a day, it may be
readily seen how impossible it would be for a milk cow to get even a
one-sided ration from cactus alone.

A ration of 40 pounds of cactus with 10 pounds of wheat bran and
12 pounds of corn stover would furnish the nutrients In somewhat
near the proper proportion. In a ration of this kind the cow would
get 21.16 pounds of organic matter, containing 1.68 pounds of pro-
tein, 11.82 pounds of carbohydrates, and 0.49 pound of fat, which is
iL) THEMIO) Oh LB Ya ree

If aration is desired in which the cactus is fed with dried brewers’
erain and cotton-seed meal, it could be made by feeding 60 pounds of
cactus with 14 pounds of brewers’ grain and 1 pound of cotton-seed
meal. In this case 20.58 pounds of organic matter are fed, containing
2.85 pounds of protein, 10.38 pounds of carbohydrates, and 1 pound of
fat. This ration would contain the nutrients in the ratio of 1:4.5. If
this ration is considered too narrow, it could be widened to good advan-
tage by feeding with it a small quantity of coarse, dry fodder, rather
than by increasing the amount of cactus.

A balanced ration of cotton-seed meal and cactus can not be pre-
pared, for if the meal be fed in just sufficient quantity to furnish the
proteids it would necessitate the feeding of too much cactus to sup-
ply the remainder of the carbohydrates. From this it must not be
inferred that a mixture of these foods would not make a desirable
ration; in fact, current successful practise has demonstrated that it
will. For example, a ration of prickly pear and cotton-seed meal was
fed to steers for one hundred and five days in a recent experiment
conducted by the Bureau of Plant Industry at Encinal, Tex., with a
gain of 1? pounds of flesh a day at a cost of only 33 cents. Any
ration of these two foods that would secure this gain each day would
contain an excess of the proteids over an amount necessary for a bal-
anced ration. Fortunately, however, an excess of proteids can be
utilized in serving the function of the carbohydrates in the animal
body, and this no doubt is what took place in the above experiment.
Usually proteids are the most expensive foods for man and beast,
and it is poor economy to substitute them for carbohydrates; yet
such a condition is not uncommon in Texas cattle feeding, where
cotton-seed meal is cheaper than other more starchy foods.

102—I

1 VALUE OF CACTI AS FOOD FOR STOCK.
RELATIVE VALUE OF THE THREE GROUPS OF CACTI.

On account of several practical considerations the prickly pears
are of much more value than either of the other two groups. They
are more numerous in the wild state, they adapt themselves to culti-
vation more readily, make a more rapid growth, and are more readily
propagated from cuttings, all of which are of vital importance in the
economic use and handling of the crop. Practically all of the Mex-
ican prickly pears are fed to stock to a greater or less extent, espe-
cially those growing where fodder is the most scarce, but there is only
one cylindrical-joimted species (Opuntia wmbricata) which is used to
any appreciable extent. The experience of the writers has shown that
Cereus giganteus is readily eaten by cattle when chopped up, but
they know of no actual feeding having been conducted with it on
any commercial scale. Mr. C. R. Orcutt states that Hchinocactus
orcuttii, which is typical of a considerable group of species, is occa-
sionally fed in Lower California. It is only in rare instances, how-
ever, that any great quantity of feed can be secured from cacti, out-
side of the genus Opuntia, and the greater part of the feed in this
genus is produced by the flat-joited forms. There are about five
species in the cylindrical-jointed group which have been fed with
some success. Opuntia imbricata, from Mexico, has been referred to,
and in various writings the use of Opuntia arborescens, Opuntia spi-
nosior, and Opuntia fulgida are mentioned. To these should be
added Opuntia prolifera from the coastal region of southern Cali-
fornia. These species constitute, without doubt, the best of the
cylindrical-jointed group, and when extent of territory covered, suc-
culence, and ease of propagation are taken into consideration Opuntia
fulgida and Opuntia wmbricata are probably the most valuable of
this group. Opuntia arborescens has a decidedly valuable character-
istic in that it extends farther to the north than any of the other
economic species of any of the groups, and it is fed to a considerable
extent in localities from southern Colorado southward.

The use of these species, however, and, in fact, the extended use of
nearly all the native species of this country and Mexico, presupposes
artificial preparation. In dry seasons in southern Arizona, cattle feed
upon the pendent bunches of fruits of the cholla (Opuntia fulgida),
but it is done at a great sacrifice of comfort. The Texas pear
(Opuntia lindhevmerr) 1s grazed to a considerable extent by cattle,
sheep, and goats without any preparation whatever, and even such
thorny forms as cardon, shown in Plate I, are grazed by cattle in
extreme cases. %

a For further discussion, see Bulletin 74 of the Bureau of Plant Industry.
102—I

g PLATE I.

. of Agriculture.

Bul. 102, Pt. 1, Bureau of Plant Industry, U. S. Dept

NoPAL CARDON (OPUNTIA STREPTACANTHA LEHM.), THE Most IMPORTANT OF THE MEXICAN PRICKLY PEARS.

VARIOUS NAMES OF CACTI IN USE. 13

COMMON AND SCIENTIFIC NAMES.

Considerable attention has been given to the popular names by
which the various species are designated, especially the larger Mexican
forms, but inasmuch as these are to be more fully considered in
another publication now in process of preparation a full discussion of
the subject is postponed.

The chaotic condition of the scientific literature and the general
imperfection of knowledge of prickly-pear forms have rendered it very
difficult to properly name the species discussed. The purpose of the
writers has been to present the exact status of their information,
indicating a doubt wherever one occurs. The Engelmann species,
which are largely United States forms, are comparatively easily deter-
mined, in most cases thru a reference to the types in the herbarium
of the Missouri Botanical Garden. In case of long-established species,
however, it is absolutely impossible to correlate the specimens with the
literature and determine what name belongs to the plant under dis-
cussion. Opuntia tuna, for instance, has been paraded in literature a
great deal, and to it has been assigned all sorts of species; but, as
pointed out by Berger and Maiden especially, no one knows what the
species is, and the writers know of no way by which its identity can
ever be determined.

Some species are referred to their proper genera only. Others
are given common names besides, but the majority of them are given
scientific names. All species receiving chemical analyses are repre-
sented in our collections by specimens mounted upon sheets in the
ordinary way or put up in boxes or in liquid. Many are growing
in conservatories or upon one of the plantations maintained by the
United States Department of Agriculture, while the seeds of many
species have been widely distributed to those interested in the scien-
tific and economic study of the group. The work is therefore well
supported by specimens to which access wil! be had in completing in
the future such naming as has not hitherto been undertaken. It was
early recognized that good dry specimens were absolutely necessary
for this work in order to make the chemical analyses and determi-
nations of permanent value.

Whenever a sample or set of samples represents a striking or con-
stant variation it is treated separately in the text; consequently
Opuntia lindheimeri, for instance, appears several times under two or
more headings. Each number or group of numbers is accompanied
by a brief set of notes made in the field beside the plant when the sam-
ples were collected, elaborated and perfected by subsequent experience.
These are presented as field notes simply and not as full technical
descriptions. This rather full set of notes, popular and scientific
names, and, as a final resort, our specimens and photographs, will
make it possible to easily verify the determinations of the writers.

102—I

14 VALUE OF CACTI AS FOOD FOR STOCK.

CLIMATIC REQUIREMENTS OF PRICKLY PEARS.

Prickly pears and other cacti are apparently inseparably connected
in the public mind with drought and heat, but this conception of the
requirements for their best development is far from perfect. Our
driest deserts produce none of these plants in economic quantities,
and the same is true of our hottest regions. Rather than say they
are adapted to conditions of extreme heat and drought, it should be
said that they thrive best in a region which has an equable tempera-
ture and a considerable rainfall periodically distributed. There is
certainly no region in the world where these plants grow naturally in
such profusion as they do upon the plateau of Mexico, but this is not a
hot country; neither is it excessively dry. It is very dry during a
large part of the year. It is a desert as compared with eastern Texas,
for instance, but it has a considerable rainfall during an average year.
The rain falls mostly in the summer, and then the country looks like
anything but a desert. The average rainfall at Zacatecas for the
past ten years, as stated by Mr. Albert L. de Lautreppe, who has
made a special study of the weather records of that city in connection
with a business venture, is 314 inches, but the average for the seasons
from January to April and from October to December is only five-
eighths of an inch to 24 inches, while the average for the other months
of the year is 34 to 74 inches a month. June, July, and August are
the rainy months, having an average rainfall of 44 to 74 inches each
for the past ten years.

While many species appear to be able to withstand high tempera-
tures, they develop naturally in the greatest profusion where the heat
is not excessive. The plateau of Mexico is a region with compara-
tively equable climate. Some species thrive under extremes of
heat. Opuntia lindhevmeri is at home in the lower Rio Grande Valley
of Texas and Chihuahua, and the closely related Opuntia engelmanni
and Opuntia engelmann cycloides thrive in southern Arizona, where
the mereury often reaches 111° F. On the other hand, there are
species which grow where the winter temperatures go to at least —40°
F., but the plants are small and of no economic importance in them-
selves except as they may be used to give a hardy character to more
valuable species. The valuable species of the Mexican highlands
thrive where the temperature falls to 14° F. in very rare instances.
Usually the freezing point is only rarely reached here. During the
past winter (1905-6) the mercury dropt at the city of Zacatecas
to 14° F., and many of the more delicate spineless forms, as well
as the natives, were badly injured. No pear was killed outright, but
the branches were frozen down for four or more joints. These rotted
and dropt off, but the old trunks survived. Opuntia lindheimer,
the common species of southern Texas, has been injured very severely
within the memory of the present generation. It suffered some injury

102—I

SPECIES OF CACTI AND THEIR ANALYSES. 15

during the winter of 1904-5. In the vicinity of San Antonio many
of the plants droopt badly after the coldest weather, which regis-
tered a temperature of 12° F. The majority of the plants straight-
ened up again, but in many the distal joints dropt off as the result
of freezing.

THE USE OF PRICKLY PEAR IN MEXICO.

In Mexico the use of the prickly pear is much more varied than in
this country. There the established plantations are guarded from
animal depredations either by rude fences or hedges of some of the
tall columnar species of Cereus or the more spiny opuntias. The
latter are planted thickly in borders around the more nearly spineless
forms, which stock eat readily.

All of the species are fed to stock indiscriminately. Whatever is
available and can be spared is singed and fed to cattle. So far as
observed, the durasnillo (Opuntia leucotricha) is preferred to all others.
This is due to some extent to its small fiber content, but more espe-
cially to its abundant delicate spines, which are singed off more
readily than those of other species which have fewer spines.

However, the extent of cattle feeding upon this kind of food is
not so great in Mexico as one would suppose from the abundance of
the material and the great extent of time during which the practise
has beenin vogue. The fact is that the average Mexican peon can not
afford to feed to stock what he himself can use so profitably in other
ways. The prickly pear is to him primarily an article of human
food, and its place can not be taken by any other plant.

The young joints as well are eaten by man in Mexico, and the
dried stems and joints are used for fuel. Of course, this fuel is
exceedingly poor, but it serves the purpose in that land where this
commodity is exceedingly scarce. The feeding of cacti to stock,
therefore, is a secondary -consideration. The lmbs which break
off and such other portions of the orchard material as can be spared
without seriously jeopardizing the tuna crop, together with such
wild forms as are available, are fed to cattle. On some of the large
haciendas, especially those devoted to maguey culture, the feeding
of pear to work oxen during the grassless season is a regular practise,
but then only wild forms are used. Overa large part of the Repub-
lic, therefore, altho the prickly pears are much used for forage, their
principal use is as an article of human food.

THE SPECIES OF CACTI AND THEIR ANALYSES.

Tn all, 67 species and varieties of cacti are discust, all of which
have been analyzed chemically, some represented by as high as five ~
samples. One hundred and eighty-seven fodder analyses and 26
complete ash analyses have been made. The following brief table
will illustrate the characteristic composition of representative
samples, together with an average of all the samples.

102—I

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AS FOOD FOR STOCK.

VALUE OF CACTI

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