THE STEM 57 



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

 other low herbage, make a way for the inflow of light. 

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

 much of the foliage, is safe from the teeth of grazing 

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

 this kind of security has had to do with the 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 through 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 stems develop wholly 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 acaulescent 

 plants offer a natural transition from the ordinary aerial t3'pe. In the 

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

 the Dandelion it may be in process of formation. 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, 173), 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, 

 between the vertical and the horizontal. 



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

 is a good example. It frequents moderately shaded situ- 

 ations, especiall}" 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 year it is covered by the leaves fallen from 

 the trees. These accumulate from season to season upon 

 the older parts of the stem, which thus finally becomes 

 partly subterranean througli burial by the leaf mold, 

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

 ity. The young, growing sections of the shoot, not more 

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

 the dead leaves, and thus remain subaerial. Such cases 



