STEMS BEARING FOLIAGE-LEAVES. 655 



the ground of forests somewhat as follows. The leaf -covered forest floor, sheltered 

 as it is by the trees, gives out but little heat, and the frost only penetrates it to a 

 slight depth in the winter, thus the tubers and bulbs are far less exposed to the 

 danger of freezing than in the open country. The early flowering and the quick 

 fading of the leaves are caused by the fact that the light required for the activity 

 of the green foliage can only penetrate to the forest ground while the crowns of 

 the trees are bare. Later, when a leafy canopy and shady roof is spread out above, 

 only a sunbeam here and there can steal through the chinks to reach the damp, 

 cool soil of the forest ground. But this scanty light would no longer suffice for the 

 work to be done by the green leaves of the bulbous plants, and they must therefore 

 achieve this before the leafly roof has developed. The weak light is, however, quite 

 sufficient for parasites and saprophytes, and it is worthy of notice that in the 

 summer in place of the green leaves of bulbous and tuberous plants, which even in 

 June have turned yellow and disappeared, the Monotropa without chlorophyll, the 

 leafless Epipogium, and a host of pale fungi spring up from the deep humus in the 

 gloom of the forest. 



o 



STEMS BEARING FOLIAGE-LEAVES. 



The foliage-stem (stirps 1 ) is characterized by the fact that the leaves borne upon 

 it are provided with green blades, and realize the popular idea of leaves. This 

 portion of the stem might indeed be called "foliage-leaf stem", and its essential 

 characteristic would be expressed in the term, but since the cotyledons frequently 

 assume the form of foliage-leaves, it is perhaps better, in order to avoid confusion, 

 to keep to the term "foliage-stem". No part of the plant is so striking to the eye 

 as the foliage-stem. The rhizomes, tubers, bulbs, and other forms of scale-bearing 

 stems are hidden from view in the earth, just like roots. The flowers borne by the 

 floral stems are ephemeral structures, the leafy stems alone retain their character 

 during the whole vegetative period as the most important portion of the plant. 

 When one attempts to reproduce the character of the vegetation of any region 

 either in words or in the form of a picture, it is to the leafy portions of grasses, 

 shrubs and trees that one confines oneself; these, blended in infinite variety, com- 

 pose the carpet of the meadow, the bush, the thicket, the woods and forests. It is 

 the style of architecture of the foliage-stem, so to speak, which expresses the style 

 of the whole plant-body. 



This peculiar style of architecture, and the habit of the whole plant subservient 

 to it, depends primarily upon the size, length and thickness of the foliage-stem, 

 is evident that in this respect conditions obtain quite analogous to those in the 



stem (stirps) ; (4) the floral stem (thalamus). 



