372 



RELA TIOM TO ENVIRONMENT. 



not necessary since flowers are not formed. The mandrake, 

 Solomon's seal, Trillium, etc., have scale leaves on the fleshy 

 underground stems, while foliage leaves are formed on the aerial 

 stems, the latter also bearing the flowers. Some of the advan- 

 tages of the rhizomes are protection from injury, food storage 

 for the rapid development of the aerial shoot, and propagation. 



Many of the grasses have subterranean stems which ramify 

 for great distances and form a dense turf. For the display of 

 foliage and for flower and seed production, aerial shoots are 

 developed from these lateral upright branches. 



III. Specialized Shoots and Shoots for Storage of 

 Food.* 



724. The bulb.— The Inilb is in the form of a bud, but the 

 scale leaves arc large, thick, and fleshy, and contain stored in 



them food products manu- 

 factured in the green aerial 

 leaves and transported to the 

 underground bases of the 

 leaves. Or when the bulb is 

 aerial in its formation, it is 

 developed as a short branch of 

 the aerial stem from which 



/-/^f'i'hmN ifei'll^^ "^'^ reserve food material is 

 V/Yf)f. \\/ -^/WliJArtkn transported. Examples are 



found in manv hlies, as Easter 

 lily, Chinese liUes, onion, tulip, 

 etc. The thick scale leaves are 

 closely overlapped and surround the short stem witliin (also 

 called a tunicakd stem). In many lilies there is a sufficient 



Fig. 425- 

 Bulb of hyacinth. 



* Besides Ihese specialized shoots for the storapjc of food, food-substances 

 arc stored in ordinarj- shoots. For example, in the trunks of many trees 

 starch is stored. With the a]iproach of cold \yeather the starch is con- 

 verted into oil, in the spring it is cnnyerled into starch again, and later as the 

 Imds lief.;in to ^row the start h is ion\-ertcrl int(^ glucose to be used for food 

 111 many otlier trees, on the other hand, the standi changes to sugar on the 

 approach of winter. 



