OF STEMS 45 



ground, bearing scale-leaves, leaf-buds and 

 roots. Those leaf-buds which grow above the 

 surface of the soil form green leaves, but 

 the underground portion of the stem bears 

 nothing but dry scales. In the arrowroot, 

 somewhat similar stems run beneath the sur- 

 face bearing dry, scaly leaver, and roots. 



4. The yam and English potato (but not 

 the sweet potato) are also enlarged stems and 

 not roots. Leaves on them are almost absent 

 being represented only by the * eyes ' which are 

 in reality leaf-buds, as is easily seen by keep- 

 ing some potatos or yams in a damp place for 

 a time, when the 'eyes' will grow, developing 

 finally into well marked steins bearing leaves. 

 Stems of the nature of the potato and yam are 

 known as tubers. The artichoke is interesting, 

 as its underground stem, with its very well 

 marked scale- leaves, serves to connect up the 

 type of stem met with in the ginger and 

 arrowroot and the true tubers. 



5. Stems also serve as the means whereby 

 plants climb. In some cases, for instance 

 convolvulus and beans, the ordinary stem 

 twines about any convenient support ; in other 

 cases, for example, passion-flower, grape vine, 

 portions of the stem are modified to form 

 special climbing organs, known as tendrils. 



