THE ROOT. 



49 



12. The tuber is an irrcfjular fleshy l)ody produced at the 

 ends of the fibres sent out from the root. They consist in the 

 po' which is the Ixjst exam[»Ie of this variety, of huds, 



in., ; il in celhilar substance consisting principally of 



starch, wljich is to become the food for the development 

 of the buds. The huds arc what are commonly called the 

 eyt's of the potatoe, and ihey form that part of it which is 

 used by the fainier lor propaijating this useful vegetable. 



Fig. 29 represents the form and 

 general arrange:iient of tubers. 



55. It is not unfrequently the 

 case that variations from the above 

 types occur ; hut the student will 

 readily, by carefully observing the 

 above definitions, determine to 

 ;) which they belong. 



13. The bulb, is a leaf bud en- 

 closed in scales or concentric lay- 

 ers, and is found either at the base 

 or summit of the stem, or in the 

 axils of the leaves ; and differs in 

 no respect from the buds hereafter 

 to be described, but in separating 

 itself from the parent and forming 

 an ind«;pendent individual. The 

 Onion and Lily form examples of this variety. Fig. 30, 

 r^O gives an illustration of (he bulb. The tree 



onion, as it is called, bears bulbs on the sum- 

 // \ mit of its stem. The buttons, as gardeners 



W ^J term them, are of this character. Some spe- 



m ^dr cies of the lily bear them in the axils of the 



leaves, and they separate from the stem and 

 fall to the earth, and become plants bearing 

 bulbs in their turn. Bulbs are sometimes dis- 

 tinguished into scaly, lx;ing covered with scales as in the lily, 



and tunicated, being formed of concen- 

 tric coats, as in the onion. 



56. At the extremities and sides of the 

 fibres of roots, small bodies are observ- 

 ed composed of lax cellular tissue, called 

 spongioles from their resemblance to sponge, 

 (see tig. 31.) it is through the spongi- 

 oles that all the nourishment of the plant 

 enters, that enters by the root. Duhamel» 

 a long time since, observed that trees ex« 



