146 



MORPHOLOGICAL DEVELOPMENT. 



by its relations to environing objects. If a branch of the 

 fungus here figured, be compared with one of the fungi 

 clustered together in Fig. 195, or, still better, with one of the 

 laterally-growing fungi shown in Fig. 196, there will be per- 

 ceived a kindred transition from radial to bilateral symmetry, 

 occurring under kindred conditions. The portion of the 

 pileus next to the side of attachment is undeveloped in this 

 branched form as in the simpler form ; and in the one case as 

 in the other, the stem is modified towards the side of attach- 

 ment. A division into similar halves, which, as shown in 

 Fig. 196 e, might be made of the whole fungus by a vertical 

 plane passing through the centre of the pileus and the axis 

 of the supporting body, might here be made of the branch, 

 by a vertical plane passing through the centre of its pileus 

 and the axis of the main stem. Among aggregates of this 

 order, the Algce furnish cases of kindred nature. In the 

 branches of Lessonia, Fig. 37, may be observed a substantially- 

 similar relationship. As their inner parts are less developed 

 than their outer parts, while their two sides are developed in 

 approximately equal degrees, they are rendered bilateral. 



§ 223. These few cases introduce us to the more familiar 

 but more complex cases which plants of the third degree of 



202 



aggregation present. At a, b, c, Fig. 202, are sketched three 

 homologous parts of the same tree: a being the leading 



