THE MORPHOLOGICAL COMPOSITION OF PLAKTS. 21 



ically. Still further pronounced becomes the compound 

 individuality, when, while the component cells of the 

 branches unite completely into jointed cylinders, the com- 

 ponent cells of the stem begin to multiply laterally, so as to 

 form an axis distinguished by its relative thickness and com- 

 plexity. 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 coherent, have undergone changes of form 

 which obscure their individualities more than before : not 

 only are they much elongated, but they are so compressed as 

 to be prismatic rather than cylindrical. This structure, be- 

 sides displaying integration of the morphological units car- 

 ried on in two directions instead of one; and besides displaying 

 this higher integration in the greater merging of the indi- 

 vidualities of the morphological units in the general individu- 

 ality ; also displays it in the more pronounced subordination 

 of the branches and branchlets to the main stem. This differ- 

 entiation and consolidation of the stem, brings all the second- 

 ary growths into more marked dependence ; and so renders 

 the individuality of the aggregate more decided. 



We might not inappropriately call this type of structure 

 pseud-axial. It simulates that of the higher plants in cer- 

 tain leading characters. We see in it a primary axis along 

 which development may continue indefinitely, and from 

 which there bud out, laterally, secondary axes of like na- 

 ture, bearing like tertiary axes ; and this is the mode of 

 growth with which Phaenogams make us familiar. But the 

 resemblance goes no further ; for these pseud-axes are devoid 

 of those lateral appendages those leaves or foliar organs 

 which true axes bear, and the bearing of which ordinarily 

 constitutes them true axes. 



185. Some of the larger Algce supply examples of an 



