

TYPES AND KINDS OF STEMS 49 



old the branching system is readily seen. In the depressions 

 the concentric rings are the scars formed by the falling away 

 of the leaves, the scars marking the point where the leaf bases 

 were attached. In these leaf scars are numerous minute pits, 

 the scars of the fibro-vascular bundles of the leaf. 



78. Crown stems, or acaulescent plants. The dandelion 

 is a good example of this kind of stem. These are sometimes 

 called "stemless" plants, and this is the meaning of acaulescent 

 plants. The plant appears to be composed only of root and 

 leaves. But there is a very short section of the stem, difficult to 

 limit, above the root and to which the leaves are attached. It 

 is at the crown of the root, and for this reason such a stem may 

 be called a crown stem. Many biennials have crown stems. 

 The beet, turnip, parsnip and carrot are also examples, but 

 because of the large, fleshy root of these plants they are some- 

 times called crown tubers. 



The crown stem of the 

 dandelion is perennial 

 and bears the foliage 

 leaves. But each year 

 it develops one or more 

 flower stems which die 

 down after the seed 

 ripens. In the fleshy 

 roots mentioned above, 

 during the second year a 

 tall leafy stem is devel- 

 oped which bears flowers 

 and seed. The fleshy Fig. 47. 



rOOtS are reservoirs for Section of onion "bulb," showing thick fleshy leaves. 



the storage of food material (see Chapter III). 



79. Bulbs. A bulb is a specialized shoot with a very short 

 stem which is covered with numerous overlapping thick leaves, 

 as in the onion, hyacinth, lily, tulip, etc. The onion bulb is 

 made up largely of broad, thick, short, fleshy leaves, or the 

 leaf bases, which overlap very closely and make a more or less 



4 



