CHAPTER 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 

 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. 



222. Fig. 201 shows us how in an aggregate of the se- 

 cond order, each proximate component is 

 modified by its relations to the rest ; just 

 as we before saw a whole fungus of the 

 same type modified by its relations to en- 

 vironing objects. If a branch of the fun- 

 gus here figured, be compared with one of 

 the fungi clustered together in Fig. 195, 

 or, still better, with one of the laterally- 



