54 PLANT RELATIONS. 



A. Stems hearing foliage leaves. 



42. General character. — As the purpose of this stem is to 

 display foliage leaves, and as it has been discovered that the 

 essential life-relation of foliage leaves is the light-relation, 

 it follows that a stem of this type must be able to relate its 

 leaves to light. It is, therefore, commonly aerial, and that 

 it may properly display the leaves it is generally elongated, 

 with its joints {nodes) bearing the leaves well separated (see 

 Pigs. 1, 4, IS, 20). 



The foliage-bearing stem is generally the most conspicu- 

 ous part of the plant and gives style to the whole body. 

 One's impression of the forms of most plants is obtained 

 from the foliage-bearing stems. Such stems have great 

 range in size and length of life, from minute size and very 

 short life to huge trees which may endure for centuries. 

 Branching is also quite a feature of foliage-bearing stems ; 

 and when it occurs it is evident that the power of display- 

 ing foliage is correspondingly increased. Certain promi- 

 nent types of foliage-bearing stems may be considered. 



43. The subterranean type. — It may seem strange to in- 

 clude any subterranean stem with those that bear foliage, 

 as such a stem seems to be away from any light-relation. 

 Ordinarily subterranean stems send foliage-bearing branches 

 above the surface, and such stems are not to be classed as 

 foliage-bearing stems. But often the only stem possessed 

 by the plant is subterranean, and no branches are sent to 

 the surface. In such cases only foliage leaves appear above 

 ground, and they come directly from the subterranean stem. 

 The ordinary ferns furnish a conspicuous illustration of 

 this habit, all that is seen of them above ground being the 

 characteristic leaves, the commonly called " stem " being 

 only the petiole of the leaf (see Figs. 45, 46, 144). Many 

 seed plants can also be found which show the same habit, 

 especially those which flower early in the spring. This 

 cannot be regarded as a very favorable type of stem for 



