28 COLLEGE BOTANY 



(1) The fundamental system or primary meristem is com- 

 posed of undifferentiated (i.e., parenchyma), actively growing 

 and dividing cells. Cells of this kind are very simple in struc- 

 ture, very rich, in protoplasm and very active during the growing 

 season. They give rise to all of the various types of cells and 

 tissues which we have just studied. In some of the lower plants 

 all the cells have this power of growth and division, but in the 

 higher plants the cells which possess this power are restricted to 

 certain locations which will be discussed in Chapter III. They 

 can be classified in two groups, the primordial meristem and 

 the cambium (see page 46). The sexual and the embryonic 

 cells also belong to this system (see Chapter VII). 



(2) The epidermal system is composed of cells which form 

 the surface covering of the plant. This system is composed of 

 modified parenchyma cells which are usually cutinized. It 

 includes the outside layer of cells of leaves and other very deli- 

 cate parts of the plant, the delicate appendages (trichomes) 

 which are found on various parts of the plant and which serve 

 for protection in some cases and for absorption in others. Sto- 

 mata and secretory cells are also found in the epidermal system 

 (see pages 78 and 81). In some plants the epidermis is appar- 

 ently made up of more than one layer of cells, but in most cases 

 of this kind the lower layers are derived from the ground meri- 

 stem and are not true epidermal cells. The epidermis on the 

 stems of perennial shrubs and trees is replaced by a cork cover- 

 ing which is frequently referred to as the epidermal system. 



(3) The fibro-vascular system is composed of fibrous tissue 

 of various kinds. It is both the strengthening and the circu- 

 latory system of the plant and is of the very greatest importance 

 in the very large and highly developed plants. 



