410 [Proc. B.N.F.C., 



series of convoluted curves. This peculiar form of vernation is 

 called circinate. Almost all our British ferns have this mode 

 of growth. The stipes is the stalk, and the lamina the leafy 

 portion. The name of frond is usually given to the upper leafy 

 portion, irrespective of the stipes, which really forms part of it. 

 The leafy part affords great variety in the mode in which it is 

 divided. Some fronds are simple or undivided, as in 

 Scolopendrium ; others again are variously divided, and are 

 named according to the degrees of division. In the majority of 

 ferns, the mature fronds are alike fertile, and are similar in 

 appearance, but in certain species the habit is to produce some 

 of the fronds wholly barren, and others wholly fertile; the 

 fertile fronds are more or less contracted. The Blechnum 

 spicant is a good example of this form. The reproductive 

 organs of ferns consist of spores, enclosed in spore cases, these 

 spore cases being collected into groups called sori. The shape 

 and position of the sori form a very distinguishing- feature in 

 determining the species. In most British ferns the sori are 

 borne on the back of the fronds. To' this there are variations. 

 The spore cases of the greater number of known species are 

 small, rounded or obovate, hollow, laterally compressed, one- 

 celled bodies, nearly surrounded by an elastic ring or belt. 

 The spores of ferns are minute, roundish, angular or oblong 

 vesicles, consisting of twO' outer layers enclosing a thickish 

 granular fluid. They are very numerous, and arranged with- 

 out order within the spore cases. So small are they that when 

 thinly scattered over a sheet of paper, they are scarcely visible 

 to the naked eye. 



The spore consists of a single cell, very tiny, of 

 various shapes in the different genera of ferns, and 

 with various markmgs, and sometimes plain, and either 

 smooth or bristling with little points. From^ the part of 

 this minute germ cell which happens to be downwards proceeds 

 the root, whilst from its upper part proceeds the frond. When 

 the spore has fallen into^ a congenial position for germination, 

 the process of development begins by the enlargement and 

 multiplication of the cell of which it consists. This cell be- 



