CHAPTEE VIII. 



THE SHAPES OF BRANCHES. 



221. AGGREGATES of the first order supply a few examples 

 of forms ramified in an approximately-regular manner, under 

 conditions which subject their parts to approximately-regu 

 lar distributions of forces. Some unicellular Algce, becoming 

 elaborately branched, assume very much the aspects of small 

 trees ; and show us in their branches analogous relations of 

 forms to forces. Bryopsis plumosa may 

 be instanced. Fig. 200 represents the f)/\n\y . 



end of one of its lateral ramifications, 

 above and beneath which come others of 

 like characters. Here it will be seen that 

 the attached and free ends differ; that 

 the two sides are much alike; and that they are unlike the 

 upper and under surfaces, which resemble one another. The 

 more highly developed members of the same group of Alga, 

 the Siphonece, show a marked radial symmetry coexisting 

 with very elaborate branching, e.g., Neo- 

 meris, Cymopolia, and others. 



222. Fig. 201 shows us how, in an 

 aggregate of the second order, each proxi 

 mate component is modified by its rela 

 tions to the rest; just as we before saw 

 a whole fungus of the same type modified 

 56 



