Ch. IV, 10] FOLTAGE-BEARING STEMS 



181 



The third and most higldy developed form of stem is found 

 where a swelhng dome of foliage is held outspread by a 

 system of stems radiating, tapering, and branching from a 

 relatively short central trunk, as well developed in our 

 common deciduous forest trees, — Oak, Maple, Elm, and 

 others (Fig. 123). Since the trunk thus melts away, as it 

 were, to the twigs, the form 

 is called deliquescent. It 

 permits a great lateral 

 spread as well as high eleva- 

 tion of the foliage, and is 

 the most effective of the 

 forms in the exposure of 

 great numbers of leaves to 

 light ; and correspondingly 

 it is the dominant forest 

 type the world over in both 

 temperate and tropical re- 

 gions. The damage which 

 would be entailed in win- 

 ter on such widespreading 

 forms by accumulation of 

 snow and ice on the leaves 

 is obviated by the shedding 

 thereof in the autumn. Here, also, a remarkable symmetry 

 of form is developed where space is sufficient, as Maples in 

 old pastures, Elms in meadows, or lawn trees attest (Fig. 

 124). In such cases the foliage has almost the form of a 

 sphere, or an ellipsoid, or a rounded cone. A crowding in 

 forests, however, produces the same effect as in the excurrent 

 type, excepting that the branches here tend to reach up to 

 a low dome or even flat top, as can be seen very clearly 

 when a deciduous forest is viewed from some mountain. 

 The effect is particularly striking where the dark spires of 

 evergreens break through the rolling plain of the deciduous 

 foliage. 



Fig. 123. — Sugar Maple, in a 

 pasture, showiuK the deliquescent 

 form. (From Bailey.) 



