SOME STRANGE GREENHOUSE PLANTS 



simple rosettes of bristles arranged about their sur- 

 face, and although it is not possible in individual 

 cases to connect the weapons they produce with 

 the particular foes against which they have to 

 defend themselves, yet the spiny and bayonet 

 protection increases according as the species in- 

 habit drier and more desert regions. 



Why some species produce a long straight stem 

 or column and others more or less globular masses 

 is also difficult to understand ; sometimes their 

 prickliness serves a double purpose, as, probably 

 in the case of the example shown in Figs. 69 and 

 70 (Plate 47), where the plant is seen to have 

 budded out numerous offshoots, all as bristly as 

 the original. 



The barbed bristles and hairs not only make 

 these offshoots unpalatable to their particular ani- 

 mal foes, but also serve to distribute the plant ; and 

 perhaps by the agency of their foes. The offshoots 

 are easily detached and cling like burs to the fur 

 and hairy paws of animals that move amongst them. 

 In this manner they are carried for considerable 

 distances, eventually being removed by the animal, 

 or falling to the ground, where they throw out 

 roots and develop. Each quaint form assumed by 

 a cactiform plant, then, is full of meaning in the 

 economy of its species. 



By way of contrast to these desert-loving cacti, 

 which, in order to live have to suppress their leaves, 

 let us turn to another plant (Fig. 71, Plate 48) 

 growing in a moister part of the greenhouse. What 

 a different story does this caladium tell ! Leaves 



lOI 



