44 



GROWTH AND WORK OF PLANTS 



Fig. 45- 

 Easter lily "bulbs." 



lower side (fig. 44). The food is stored in the fleshy leaves. It 

 is of a proteid or nitrogenous nature, i.e., it contains nitrogen in 

 addition to carbon, hydrogen, and oxygen. The presence of pro- 



teids can be shown by heating 



portions of an onion in nitric 

 acid. The liquid becomes 

 pale yellow in color. Adding 

 a small quantity of ammonium 

 hydrate the color becomes 

 orange. The lily bulb (caster 

 lily, fig. 45) is similar to that 

 of the onion but the thickened 

 leaves are not so closely and 

 ompactly crowded. 



74. The corm. This is a short, thick, fleshy shoot in which 

 food is stored. The Indian turnip, or Jack-in-the-pulpit, is a 

 good example. This is circular and somewhat flattened or oval. 

 It is perennial, increasing gradually in size usually each year on 

 the upper side, while the lower side gradually dies off. Prop- 

 agation of the corm usually takes place by the formation of 

 small corms on the side. These eventually separate and form 

 new plants. New corms are also formed by the germination of 

 the seed. 



75. Tubers. A tuber is a fleshy thickened portion of a 

 subterranean stem containing large quantities of plant food. 

 There are rudimentary scale leaves, in the axils of which are 

 buds. These buds often resemble an eye, as in the potato tuber, 

 when they are called " eyes." The potato plant has slender 

 underground stems as well as aerial stems. It is on the ends of 

 these underground stems, which are thicker than the roots, that 

 the potato tuber is formed. Some of the starch that is made in 

 the leaves during the day is transported to these underground 

 shoots and stored up in the tuber. 



76. The potato is an interesting plant to study. The 

 potato plant is propagated by planting the tubers, or pieces of 

 them containing the eyes. Tubers kept in a warm room during 



