MORPHOLOGY 



147 



to the natural system, with the other lower Cryptogams in the class 

 of cellular plants, as distinguished from the VASCULAR plants or 

 Pteridophytes and Phanerogams. A separation of the tissues into the 

 three systems of tegumentary, fundamental, and vascular tissue occurs 



Fig. 150. — Transverse section of the stem of Milium uiidulatum. I, Conducting-bundle ; c, cortex ; 

 i, peripheral cell layer of cortex ; /, part of leaf ; r, rhizoids. ( x 90.) 



for the first time in the vascular plants ; while the systems themselves 

 also exhibit a widely extended differentiation. 



The Ontogeny of the Internal Structure 



However a plant may arise, whether from an asexually produced 

 spore or from a fertilised egg, its first inception is always as a single cell. 

 In unicellular, spherical, or rod-shaped organisms, such as Gloeocapsa 

 polydermatica (Fig. 1) or Bacteria (Fig. 4), the whole course of develop- 

 ment is concluded with the cell division which gives birth to two 

 new independent organisms. If the cell divisions be continuous 

 and parallel, and the newly-developed cells remain in contact, 

 cell filaments (Fig. 4, a*) will be formed ; if the division walls 

 have different inclinations, and are at the same time all in the 

 same plane, CELL SURFACES are produced ; and if the walls are 

 formed in three dimensions of space, cell MASSES are the result. 

 Such an organism will attain but a low degree of development 

 if all its cells have a like value, and continuously reproduce 

 themselves in the same manner. With the distinction into base 

 and APEX a plant manifests a higher degree of differentiation. A 



