154 BOTANY PA3CI i 



more rapidly growing portions. In the Anthocerotaceae and Bryineae, 

 on the other hand, stomata similar in structure to those of the 

 Pteridophytes and Phanerogams are found in the outer cell layer of 

 the spore capsules. It would seem, however, that these stomata of 

 the Bryineae are probably not homologous with those of higher 

 plants. It is more reasonable to regard them as merely analogous 

 formations, such as from internal causes so often occur in the 

 evolution of organs. In the stems of many of the Bryineae there is 

 also developed a simple form of conducting bundle (Fig. 161); and 

 the many-layered midrib of the single -layered leaf lamina is al>i> 

 traversed by a conducting strand. In spite of their more advanced 

 differentiation, the Bryophytes may still be included, just as they 

 were originally in 1813 by AUGUSTE PYUAME DE CANDOLLE ( 14 "'), in 

 his classification of the vegetable kingdom according 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 epidermal, fundamental, and vascular tissue occurs for 

 the first time in the vascular plants associated with the development 

 of roots ; while the systems themselves also exhibit a widely extended 

 division of labour. 



The Ontogeny of the Internal Structure 



Just as the phylogenetic development of the vegetable kingdom 

 has proceeded from the simple to the complex, every plant in its 

 ontogeny passes through a corresponding development. The study of 

 the ontogenetic development is termed embryology. The early stage 

 of a new plant body is called the embryo or germ, and its further 

 development is spoken of as germination. 



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 development is concluded with the cell division which gives birth 

 to two new independent organisms (Fig. 1). 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. With the distinction into BASE and APEX a plant 

 manifests a higher degree of differentiation. A VEGETATIVE or 

 GROWING POINT is then developed, usually at the apex (Fig. 5). 

 This retains its embryonic nature, while the parts produced from it 



