460 



CACTUSES IN- DOORS AND OUT. 



them. They are also covered with a very hard epi- 

 dermis, which serves the same purpose of preventing 

 evaporation, and most of the species are clothed with 



^^■-4il;f/i/// 



Mamillaria micromeris. 



numerous spines and hairs which also check the loss of 

 moisture. These spines and hairs are nearly always 

 characteristic of desert plants. Some have supposed 

 that one of their chief functions is to protect the plant, 

 for any animal which frequents desert regions would be 

 very greedy of any plant which contains much mois- 

 ture. Yet not all of cactuses have spines. There are 

 some species even in arid regions which are perfectly 

 smooth, but in such cases the epidermis is probably thick 

 enough to sufficiently check evaporation. Cactuses 

 might be called vegetable jugs. 



The armament of the cactuses is itself exceedingly vari- 

 ous. It is oftenest made up of sharp and stiff spines. 

 These vary in kind and number and manner of 

 insertion. The number borne upon a tubercle is 

 usually characteristic of the species. Two mam- 

 illarias show these differences. I\T. iiiicroDuris 

 (Fig. E), i. £'. , "small parts," has from 20 to 40 

 small spines upon each tubercle, while M. niacro- 

 niei-is (Fig, A ), " large parts," has only about half 

 the number and they are very large and strong^ 

 M. macromci is is one of the largest flowered of all 

 mamillarias. In fact, the flower is almost equal 

 in size to the body of the plant. The covering of 

 the old-man cactus [Cereiis or Pilocereus senilis, 

 Fig. CC) is mostly composed of long and white 

 hair-like locks, while some species, particularly 

 the opuntias, possess many small prickles which 

 are detached by the touch and quickly enter the 

 flesh. An old-man cactus was once estimated to 

 bear 72,000 bristles, and upon a certain echino- 

 cactus they were reckoned at 51,000. 



The flowers of the cactus tribe are always sin- 

 gular and interesting, perhaps the more so because 

 they are so entirely unlike in expression to the 

 plants upon which they are borne. If the plants 

 remind one of the most scorching deserts, the flow- 

 ers, on the other hand, recall the choicest blossoms of the 

 conservatory and the garden. They are exceedingly va- 

 ried in form and color and size. The blossoms of the 

 night-blooming cereus and the phyllocacti are among the 



most attractive and showy of flowers, while those of the 

 rhipsalis are often inconspicuous. Yet this showy char- 

 acteristic of the cereus flowers is by no means common to 

 even the cereus tribe. The flowers of some of the species 

 are small and almost green. Fig. Q, Cereus chlorantlms, 

 represents a species which has yellowish-green flowers, 

 and their diminutive size can be understood when it is 

 known that the entire plant rarely exceeds ten inches in 

 height. This figure should be compared with Fig, A, 

 which shows plants of the same genus, and with S, one 

 of 1 the night-blooming cereuses of the gardens. These 

 dissimilarities are but a few of the surprises which 

 abound in this singular family, and which render it ex- 

 tremely attractive to the student of nature's wondrous 

 and never-ceasing diversity and beauty. 



The cactuses are peculiarly American plants. There is 

 but one of the thousand described species which is in- 

 digenous to other countries, and that one is so unlike 

 ordinary cacti that one would scarcely think of associ- 

 ating it with them. This plant is a rhipsalis, closely 

 allied to the mistletoe cactus of greenhouses. The home 

 of the cactus family is in the deserts of the southwestern 

 United States and Mexico and the Andean region of 

 South America, They appear to have been developed 

 through long ages to suit the peculiar climates of those 

 regions. In other desert regions there are plants which 

 are similar in form and yet very different in botanical 

 character. This is particularly true of the great desert 

 region of southern Africa, which is inhabited by many 



Fig. F, Mamillaria macromeris. 



plants so nearly like the cactuses as to be mistaken for 

 them by the ordinary observer, but which belong to an en- 

 tirely different division of the vegetable kingdom. These 

 cactus-form plants are euphorbias, many species of which 



