10 SILVA OF NORTH AMERICA. CACTACEZ. 
at the apex, by a loose papery sheath, on a few species broad, flat, fleshy, and spreading,’ rarely thin, 
flat, paper-like, and elongated.? Flowers lateral, produced from areole on branches of the previous 
year between the bristles and spines, sessile, diurnal, or rarely nocturnal, cup-shaped, often large and 
showy. Calyx-lobes numerous, flat, erect, deciduous. Corolla rotate ; petals numerous, obovate, united 
at the base, spreading, red, yellow, or purple. Stamens numerous, shorter than the petals, inserted 
in many series on their base; filaments filiform, free or slightly united below; anthers oblong, two- 
celled, opening longitudinally. Ovary inferior, one-celled; style cylindrical, longer than the stamens, 
obclavate below, fistular above, divided at the apex into from three to eight elongated or lobulate lobes 
stigmatic on the inner face; ovules indefinite, horizontal, anatropous, inserted on numerous parietal 
placentas. Fruit baccate, sometimes proliferous, covered by a thick skin, succulent and often edible, or 
dry, pyriform, globose or elliptical, concave at the apex, surmounted by the marcescent tube of the 
flower, tuberculate, areolate or rarely glabrous, truncate at the base with a broad umbilicus.® Seeds 
numerous, immersed in the pulpy placentas, compressed, discoid, often margined with the bony raphe; 
testa bony, white, sometimes marked by a narrow darker colored marginal commissure. Embryo coiled 
around the copious or scanty albumen ; cotyledons large, foliaceous; radicle thin, obtuse, turned toward 
the hilum.‘ 
Opuntia, which originally was confined to America, has now become naturalized in many of the 
warm dry regions of the world.» About one hundred and thirty species are now recognized.® They are 
1 Subgenus 651 
(1898). 
2 The broad-spi 
to Argentina, and are still very imperfectly known. (See W. Wat- 
son, Gard. Chron. ser. 3, xxiii. 339, f. 129.) 
8 Professor Toumey suggests (in litt.) that the so-called fruit of 
Opuntia is really a terminal branch of the joint containing the 
Peireskiopuntia, Schumann, Monog. Cact. 
d species (Platy 
the) appear to be confined 
ripened ovary which is sunken into its apex, and that the mor- 
phology of the fruit of the whole Cactus family is probably simi- 
lar. In some cases the ovary-bearing branch is highly modified. 
In certain species, however, particularly in the cylindrical stemmed. 
Opuntias, it resembles a sterile terminal joint in all respects, except 
in the concave flower-scar at the apex. The proliferous character 
of the fruit, a character common in a greater or less degree to 
nearly all species of Opuntia, and occasionally found in other 
genera, would seem to indicate that this view is correct. Opuntia 
spinosior and Opuntia versicolor frequently produce proliferous fruits, 
and those of Opuntia fulgida are almost constantly proliferous. In 
the case of these species plants can be propagated by using the 
green fruits and even the ripe fruits as cuttings. Occasionally 
flat-stemmed Opuntias are found with an ovary developed in the 
apex of a branch resembling in all respects one of the narrow 
flat sterile stems of the plant. In Opuntia versicolor the ovary is 
frequently in the apex of a long joint, and there are innumerable 
transitions between these long fruit-joints and the typical pear- 
shaped fruit of the species. Ovaries in such stems are generally 
sterile, but occasionally contain one or many seeds. 
4 By Engelmann the species have been arranged in the following 
subgenera : — 
Puatopuntia (Proc. Am. Acad. iii. 289 [1856]), now usually 
extended to include his Stenopuntia (J. c.). 
Joints of the branches compressed, without a woody skeleton ; 
spines without sheaths. Fruit pulpy or rarely dry; raphe form- 
ing a prominent and bony margin round the seed. Embryo curled 
round the scanty albumen ; cotyledons contrary to the sides of the 
seed. 
CyLinproruntiA (Engelmann, J. c. [1856]). 
Joints of the branches cylindrical or clavate, more or less tuber- 
culate, with or without a solid or tubular and reticulated ligneous 
skeleton. Spines inclosed in a loose sheath or in some species 
Seeds hard- 
shelled, smooth, often marked by a conspicuous marginal commis- 
sure, usually marginless, embryo forming less than a circle round 
naked. Fruit fleshy or dry, setulose or spinescent. 
the copious albumen ; cotyledons contrary, oblique, or parallel to 
the side of the seed. 
5 Opuntias were probably among the first plants carried from 
America to the Old World, where they soon became naturalized in 
southern Spain; from Spain they were carried by the Arabs to 
northern Africa, and they have gradually and generally extended 
through all the warm dry parts of the world. (See A. de Candolle, 
Origine des Plantes Cultivées, 218.) 
In some countries naturalized Opuntias have become dangerous 
weeds, destroying the value of the land which they occupy with 
In New South Wales, 
where the Opuntia was introduced more than a century ago, differ- 
impenetrable thickets of spiny branches. 
ent species have become such pests that in 1886 an act was passed 
compelling persons, under penalty of fine and imprisonment, to 
clear their land of these plants. (See Maiden, Agric. Gazette New 
South Wales, ix. 979.) In South Africa Opuntias have spread to 
such an alarming extent that their destruction has been a subject 
of serious government investigation. (See Kew Bull. Miscellaneous 
Information, July, 1888, 165 ; September, 1890, 186.) In India, 
where Opuntias have long been naturalized, it is supposed through 
early Portuguese introduction, they spread rapidly and are con- 
sidered dangerous weeds (see Brandis, Forest Fl. Brit. Ind. 246); 
and in southern Texas hundreds of square miles of grazing land 
have been overrun and entirely ruined by different species of dwarf 
Opuntias. (See Bentley, U.S. Dept. Agric. Farmers’ Bull. No. 72, 14 
[Cattle Ranges of the Southwest].) On the other hand, the roots of 
Opuntias are said to have disintegrated the lava on the slopes of 
Mt. Aitna in Sicily, and, enriching it by the decay of their stems, 
to have gradually changed barren wastes into productive vineyards. 
(See Bois, Bull. Soc. Nat. d’Acclimatation de France, sér. 4, v. 643.) 
6 See De Candolle, Prodr. iii. 471. Seemann, Bot. Voy. Herald, 
293. — Engelmann, Proc. Am. Acad. iii. 289; Bot. Mex. Bound. Surv. 
ii. 45 ; King’s Rep. v. 118; Brewer § Watson Bot. Cal. i. 247. — 
