THE STEM 57 



the form of a rosette, and pressing back the grass and 

 other low herbage, make a wa}' for the inflow of hght. 

 At the same time the stem, with the growing point and 

 niueh of the fohage, is safe from tlie teetlr of grazing 

 animals: though it would be hard to say just how mneh 

 this kind of security has had to do with tlie development 

 of the shortened stem. For other advantages of the acau- 

 lescent habit may have played a part in the gradual acquire- 

 ment of a shortened stem througli successive generations 

 of Dandelionlike plants ; such as the increased moistness 

 of the half-subterranean situation, and the relatively stable 

 temperature of the soil. 



83. Certain steins develop whollj' beneath the surface, as we shall 

 presently see, the leaves alone, with the flowering axis, appearing above 

 ground. To such forms as these the Dandelion and other acanlescent 

 plants offer a natural transition from the ordinary aerial type. In the 

 buried stems tlie lialiit of taking refuge in the soil is fully formed. In 

 the Dandelion it may he in process of foniration. At least we may 

 see in the latter one stage in the change of habit by which the Jack- 

 in-the-pulpit, for example (Figs. 50, 17o), has become, as to its stem, 

 a confirmed dweller beneath ground. 



84. Thus far only vertical stems, or stems of a more or 

 less upright character, have been considered. There are 

 all gradations between these and prostrate or horizontal 

 forms, many species habitually taking a leaning attitude, 

 lietween tlie vertical and tlie liorizontal. 



85. Of the creeping, or repent, kinds the Partridge Berry 

 is a good example. It freqtients moderately shaded situ- 

 ations, especially open woods, where it runs along upon 

 the ground, striking root at short intervals and spreading 

 its small, rounded, evergreen leaves quite close to the sur- 

 face. Each j'car it is covered by the leaves fallen from 

 the trees. These accumulate froiu season to season upon 

 the older parts of the stem, which thus finally becomes 

 partly subterranean through burial by the leaf mold, 

 loses its leaves, and gradually decays at the older extrem- 

 ity. The young, growing sections of tlie slioot, not more 

 than a year or two old, pusli forward continually, over 

 tlie dead leaves, and thus remain subaerial. Such cases 



