28 MORPHOLOGICAL DEVELOPMENT. 



dichotomously-branched form, and so gaining a more specific 

 character as well as greater size. 



Where, as in types like these, the morphological units 

 show an inherent tendency to arrange themselves in a manner 

 which is so far constant as to give characteristic proportions, 

 we may say that there is a recognizable compound individual- 

 ity. Considering the Thallophytes which grow in this way 

 apart from their kinships, and wholly with reference to their 

 morphological composition, we might not inaptly describe 

 them as pseudo-foliar. 



184. Another mode in which aggregation is so carried 

 on as to produce a compound individuality of considerable 

 definiteness, is variously displayed among other families of 

 Alga. When the cells, instead of multiplying longitudinally 

 alone, and instead of all multiplying laterally as well as 

 longitudinally, multiply laterally only at particular places, 

 they produce branched structures. 



Indications of this mode of aggregation occur among the 

 Confervoidece, as shown in Figs. 22, 23. Though, in some of 

 the more developed Algce which exhibit the ramified arrange- 

 ment in a higher degree, the component cells are, like those 

 of the lower Algce, united together end to end, in such way 

 as but little to obscure their separate forms, as in Cladophora 

 Hutcliinsice, Fig. 31 ; they nevertheless evince greater sub- 

 ordination to the whole of which they are parts, by arranging 

 themselves more methodically. Still further pronounced 

 becomes the compound individuality when, while the com- 

 ponent cells of the branches unite completely into jointed 

 cylinders, the component cells of the stem form an axis dis- 

 tinguished by its relative thickness and complexity. Such 

 types of structures are indicated by Figs. 32, 33 figures 

 representing small portions of plants which are quite tree- 

 like in their entire outlines. On examining Figs. 34, 35, 36, 

 which show the structures of the stems in these types, it 

 will be seen, too, that the component cells in becoming more 



