THE DIFFERENT KINDS OF STEM. 



27 



their rudimentary character as a protective covering to the 

 inner leaves, which grow in a tuft from the earth's surface, the 

 flower stem rising from their centre. 



In the tunicated bulb the scales enclose each other in a con- 

 centric manner, each scale embracing the entire circumference 

 of the bulb. The outermost scales are thin and dry, the inner- 

 most thick and succulent. Tunicated bulbs are restricted to 

 such plants as have sheathing leaves, and which, consequently, 

 embrace at their base the entire circumference of the stem. In 

 the scaly bulb the scales are free from each other and much 

 smaller, being imbricated, or lying one on the other, like the 

 tiles of a house. This bulb belongs only to plants, the leaves 

 of which are sessile, and therefore not connected with the 

 stem by a sheathing base. 



Fig. 6. 



Fig. 7. 



Fig. 6. Bulb of the garlic with a crop of young bulbs. 

 Fig. 7. Axillary bulblets, b, of Lilium bulbiferum. 



Bulbs being subterranean buds or undeveloped stems, give 

 birth to new buds or bulbs in the axils of their scales, the 

 rudimentary leaf-like nature of which is thus rendered apparent. 

 The young bulbs are called cloves. This mode of increase, is 



