40 GLIMPSES INTO PLANT-LIFE 



in a thick leathery skin, which protects the plant 

 from the burning heat of the sun. Very little 

 moisture escapes through this thick green epi- 

 dermis ; therefore when rain falls the plants receive 

 and store up their liquid food, and live sparingly 

 upon it during the long periods of drought, which 

 last for three-quarters of the year. Some of these 

 cacti, as we see them at Kew, are tall, straight- 

 stemmed plants, others low-growing rounded 

 masses, little s[)in\' cushions, almost like vegetable 

 hedgehogs. 



In the arid prairies of Texas, advantage is taken 

 of the water}' stores of the cactus, for when other 

 sujjplies fail, its fleshy stems arc cut open, and 

 hcjr.ses and cows greedily devour the succulent 

 food, which answers the purpt)se of drink, as well 

 as affording nutritious fodder. 



Oin- British spurge-plants ha\e green lea\es, 

 a thin epidermis, and all the ordinary characters 

 (il the |)lants of a temperate region, but b}' com- 

 paring them with the s])urges found in Madeira, 

 we see how climate cau.ses adaptation to differing 

 conditions. One of these spurges growing in my 

 greenhouse has a tall column-like stem, no leaves, 



