THE CELLS OF MOSSES. 3 



the Mosses or Musci, which are what I allude to, are of all tribes 

 of plants the best adapted for studying how vegetable cells come 

 into existence, increase in size, multiply, and reach maturity • 

 because Mosses in all the early stages, and in many of the later 

 conditions of their growth, are mostly of a semi-transparent 

 nature, while they have this great advantage, that the various 

 stages of growth can be found at every time of the year, and 

 almost everywhere ; to which is to be added, that nearly all of 

 them have the peculiarity of reviving, as it were, after being dried, 

 their cells taking up water the moment they come in contact with 

 it, and swelling to their original size, even though the plant may 

 have been kept perfectly dry for years. Owing to this, it is 

 actually possible to intermit the study of the Mosses for a shorter 

 or longer period, and that with the same specimen, and to resume 

 it almost where one left off. 



Thus we can start with the single cell of the germinating 

 spore of a moss, and trace it up step by step through the proto- 

 nema and the prothallium stages, till we find it developing into a 

 little budlet of leaves, the beginning of the plant, of leaf, and 

 stem, and branches, and capsule-crowned seta. For this purpose, 

 specimens can be readily found in abundance in spring and early 

 summer, on damp clay under trees, and the shady side of ditch- 

 banks, and open field-drains, where the green stratum, covering the 

 earth like a thick emerald cobweb, will usually furnish every stage 

 of growth : — The single germinating cell ; the tubular bulging of 

 its inner coat; and its dividing transversely, as the cells multiply by 

 the growth which takes place only at the apex of the filamentous 

 shoot, or branch ; and the origin of the buds which eventually 

 develop into the leafy plant. 



These protonema growths will furnish examples of complete 

 cells, in which can be found, according to their age and develop- 

 ment, these three parts : — i. The firm, elastic, outer, enclosing 

 membrane, called the cell-ivall ; 2, The soft, inelastic, semi-fluid 

 substance inside the cell-wall, called the protoplasm^ in which is 

 generally imbedded a more solid, rounded body called the nucleus; 

 and 3, The cell-sap^ which is a watery fluid occupying the centre. 

 In the protoplasm will be found the chlorophyll granules or 

 colouring grains, which give the green colour to vegetable or 



