6,8 THE GENERAL DEVELOPMENT OF PLANTS. 



composed of slender cells which grow in a downward direction, and 

 doubtless perform their part in absorbing moisture. A Moss, there- 

 fore, is like an ordinaiy herb in minia- 

 ture, and exhibits tlie three general 

 Organs of Vegetation, viz. Root, 

 Stem, and Leaves. 



111. Cellular and Vascular Plants. 



"While the Mosses emulate ordinary- 

 herbs and trees in vegetation and ex- 

 ternal appearance, they accord with 

 the lowest kinds of plants in the sim- 

 plicity of their anatomical structure. 

 They are entirely composed of cellu- 

 lar tissue strictly so called, chiefly in 

 the form of parenchyma (51) ; at least 

 they have no distinct vessels or ducts 

 (57) and no true wood in their com- 

 position. The Mosses, along with the 

 Lichens, AlgfE, Fungi, «fec., were there- 

 fore denominated Cellular Plants 

 by De Candolle. All plants of higher 

 grade, inasmuch as vascular and woody 

 tissues enter into their composition, 

 when they are herbs as well as when 

 they form shrubs or trees, he distinguished by the general name of 

 Vascular Plants. 



112. The strength which woody tissue imparts (54) enables 

 plants in which it abounds to attain a great size and height ; while 

 Mosses and other cellular plants are of humble size, except when 

 they live in water, in which some of the coarser Sea-weeds do indeed 

 acquu'e a prodigious length. Although true Mosses have no wood 

 in their composition, yet the so-called Club-Mosses have. So also 

 have the Ferns, the highest organized family of the lower grade of 

 plants ; and although these are mostly herbs, or else plants with 

 their more or less woody stems creeping on or beneath the surface 

 of the ground, yet in warm climates some species rise with woody 

 trunks into tall and palm-like trees. But even these, like the hum- 



FI6. 98. An individual of a Moss (Physcomitrium pyriforme), enlarged to about twelve 

 times the natural size. 99. Tip of a leaf, cut across, much magnified, to show that it is made 

 up (except the midrib) of a single layer of cells. 



