CHAPTER IX 

 THE NON-VASCULAR PLANTS 



69. Introductory. We have been considering seed plants 

 exclusively. It is time to consider also the plants which 

 do not bear seeds. In doing so we shall follow what is called 

 the evolutionary sequence; that is, we shall begin 'with 

 plants whose structure is very simple and proceed from them, 

 as evolution proceeded, to those whose structure is com- 

 plex. We shall go from the lowest plants to the highest. 



All plants may be grouped into those which have a vas- 

 cular system and those which do not. It is quite certain 

 that those without a vascular system preceded those which 

 have it; those which have it evolved from forms which 

 were without it. So we will begin by considering the non- 

 vascular plants. 



Since wood is a part of the vascular system, the non- 

 vascular plants are, of course, not woody. They are all 

 soft plants of little height. Mosses and mushrooms are 

 examples of the non-vascular plants, while ferns and seed 

 plants are examples of those which are vascular. 



70. The Four Great Divisions. The plant kingdom is 

 divided into four great groups. Those plants which com- 

 pose the two lower or simpler of these divisons have no 

 vascular system ; those which compose the two higher or 

 more complex divisions are plants in which we find a vas- 

 cular system. 



360 



