58 A DESERT FRUIT. 



dronglits of its almost rainless habitat by flrinldng as 

 much as it can when opportunity offers, hoarding up the 

 superfluous water for future use, and economisiug 

 evaporation by every means in its power. 



If you ask that convenient fiction, the Man in the 

 Street, what sort of plant a cactus is, he wuU probably 

 tell you it is all leaf and no stem, and each of the leaves 

 grows out of the last one. Whenever we set up the Man 

 in the Street, however, you must have noticed we do 

 it in order to knock him down again like a nine-pin 

 next moment : and this particular instance is no 

 exception to the rule ; for the truth is that a cactus is 

 practically all stem and no leaves, what looks like a leaf 

 being really a branch sticking out at an angle. The true 

 leaves, if there are any, are reduced to mere spines or 

 prickles on the surface, while the branches, in tlie 

 prickly-pear and many of the ornamental hot-house 

 cactuses, are flattened out like a leaf to perform foliar 

 functions. In most plants, to put it simply, the leaves 

 aro the mouths and stomachs of the organism; their 

 thin and flattened blades are spread out horizontally in 

 a wide expanse, covered with tiny throats and lips which 

 suck in carbonic acid from the surrounding air, and 

 disintegrate it in their own cells under the influence of 

 sunlight. In the prickly pears, on the contrary, it is the 

 flattened stem and branches which undertake this essen- 

 tial operation in the life of the plant — the sucking-in of 

 carbon andgiving-out of oxygen, which is to the vegetable 

 exactly what the eating and digesting of food is to the 

 animal organism. In their old age, however, the stems 

 of the prickly pear display their true character by be- 



