BUDS AND STEMS 



121 



Leaflike Stems. — An exami- 

 nation of tlie hothouse smilax 

 (M yrsiphyllum) shows us that the 

 structures which at first sight ap- 

 pear to be leaves are really green, 

 leaflike branches. This we know, 

 because immediately below each 

 cladophyll, as the leaflike branch 

 is called, we find a tiny scale, evi- 

 dently the leaf. The cladophyll 

 occupies the same position with 

 relation to the leaf that a bud 

 which develops into a lateral 

 branch would occupy. Thus we 

 see it is homologous to a branch. 



Roots and Stems as Food. — 

 Underground stems and roots form 

 some of the most important sources 

 of man's food supply. Our com- 

 monest foods, as the potato, sweet 

 potato, carrot, parsnip, turnip, and 

 beet, are well-known examples. 

 Onions contain considerable pro- 

 teid material. The sago palm is 

 the chief support of many of the 

 natives of Africa. Each adult 

 tree will furnish 700 pounds of 

 sago meal, 2^ pounds being 

 enough to support a man one 

 day. The cassava root, from which 

 tapioca is made, is one of the 

 main supports of African natives. 

 Sugar, obtained from the stem 

 of the sugar cane and from the beet root, is a world-known commodity. 



The following table shows the proportion of foods in some of the com- 

 moner roots and stems: — 



1 2 



Stems of honey locust (i) and black locust (;2) ; 

 Z/5, leaf scars; the thorns (S) on the honey 

 locust are modified stipules (parts of leaves); 

 the thorns ( T) on the black locust are modi- 

 fied branches. 



Potato 75.0 



Carrot 89.0 



Parsnip , . 81.0 



Turnip 92.8 



Onion „ , 91.0 



Sweet Potato ...... 74.0 



Beet §2.2 



