38 STEMS AND BUDS 



very prominent^ as in the easo of the liyacintli or onion, or they 

 may be small and on a very short, thick, fleshy stem, as in the 

 case of the Indian turnip. This last type is known as a conn. 



Bulbs or bulblets are sometimes borne on the stem above 

 ground; they are nothing more nor less than modified buds. 



Sometimes the underground stems become very thick and 

 fleshy and are known as tubers. The common white or Irish 

 potato is an excellent example of the tuber. The so-called 

 " eyes " are buds and indicate the nodes of the stem. True 

 tubers, such as the Irish potato, are fleshy stems and are entirely 

 different from the fleshy roots of such plants as the s\veet potato 

 and the dahlia. 



Two Chief Uses of Stems. — As previously stated, stems con- 

 nect the roots with the leaves and support the latter in the air 

 and light, but some plants, such as the cactus, have leaves that 

 are poorly developed and of little importance. The stems of 

 these so-called " leafless " plants are green and serve the same 

 function as leaves. (Page 47.) The stems of many other plants 

 are also green and perform the duties of lea^'es for a part or for 

 the entire life of the plants. The young twigs are usually green 

 and have stomata (Chapter IV), the same as leaves. How- 

 ever, these stomata soon lose their original character, and de- 

 velop into lenticles. (Chapter VIII. ) The lenticles are the 

 little specks which are so readily recognized on the smaller twigs. 

 (Figs. 20, 21 and 30.) They will be referred to again. 



Stems also serve for the passage of the water and food sub- 

 stances from one part of the plant to another. (Chapter VIII.) 

 These are the primary functions of stems, but they also serve 

 many other purposes. In the cacti and other plants living in 

 very dry regions they serve for the accumulation of considerable 

 quantities of water. Floating plants frequently have large 

 chambers filled with air which increases their buoyancy. Many 

 stems, such as tubers, serve for the accumulation of food sub- 



