INTRODUCTION. 



In the lowest orders of plants reproduction takes place by the developement 

 of cells, which being set free by the bursting of the parent cell, enclosing 



Fig. 34. Pig. 36. 



Protococcus nivalis, show- 

 ing cells and vesicles, 

 partly embedded in a 

 slimy jelly. 



Fig. 35. 



Fig. 37. 



Hydnum castrensis. Feather moss. 



Marchantia polymorpha. 



them, become independent beings, capable of producing others in the same 

 manner. In somewhat higher tribes, only a small portion of the cells of 

 which they are formed, have this reproductive power, and they are always 

 found in certain and definite parts of the plant ; these cells are called spores, 

 and this form of reproduction occurs in the sea weeds, 

 lichens, and fungi, &c. In some of the liverworts there 

 is a distinct set of organs of fructification. The little 

 bodies forming radii on them are spore cases ; these when 

 mature, burst and scatter their contents or spores, which 

 originate new plants, their outer coat rupturing, and the 

 inner projecting in a long tube filled with new cells ; these 

 increase into a leafy projection, from the lower part of 

 which, root fibres proceed. 



In mosses the organs of reproduction are more com- 

 plex. There are small capsules or urns on long stalks, 

 furnished with lids which fall off when the spores con- 

 tained in them are mature ; these spores are developed 

 round a columella. After being scattered on the earth, 

 the outer coat of these spores ruptures, and several mi- 

 nute tubes are projected, each of which contains gra- 

 nules, each capable of forming a new plant. In the 

 ferns the spore cases are found on the backs or edges of 

 the leaves, disposed in various forms, these cases are filled 

 with a fine brown dust, which is scattered on their burst- 

 ing. This dust is composed of spores which vegetate in 

 a peculiar manner; at first the outer coat is ruptured, and 

 the inner one projects in a long tube, within which, as 

 well as in the original cavity, new cells are formed from 

 the included germs. These cells at first coalesce and form 



Polypodium vulgare, or 

 Wall Fern. 



