THE FEUN TUini:. 



269 



midrib, and that, sometimes, one of the branches 

 forks again. This kind of vein is peculiar to Ferns, 

 and will enable you, at all times, to recognise them 

 whether their reproductive parts are present or not. 



After the leaf has been growing some little time, 

 you may remark a number of narrow pale bands 

 appearing at pretty equal intervals upon some of the 

 veins, and following their direction {fig- 1. «•)• P^^' 

 sently afterwards the whole of the skin of the leaf, 

 where these bands are, separates from the green part 

 below it : in course of time, something swells and 

 raises up the skin, till at last it bursts through it, 

 separating the skin into two equal parts, one edge of 

 which remains adhering to the leaf {fig. 2. a. a.). At 

 this period this cause of the swelling is discovered ; it 

 consists in a multitude of brown seed-like grains that 

 are crowded together very closely, and form a brown 

 ridge {fig. 3. a. a.). Botanists call the skin which 

 separates from the leaf the indusium, the ridge sorus, 

 and the seed-like grains thecte. In order to gain a 

 distinct view of all these parts, you should cut through 

 the leaf across the sorus, just after the indusium has 

 burst ; and then the edges of the indusium will be dis- 

 tinctly visible {fig. 4. a. a.), with the ridge-like recep- 

 tacle of the thecse rising up between them {fig. h. b.). 



The only means of propagating itself, which the 

 Hart's-tongue possesses, resides in the thecse. It has 

 no calyx, corolla, stamens, or pistillum, and conse- 

 quently neither fruit nor seed ; nevertheless it can 

 perpetuate its kind with the same certainty as the 

 most perfect plant. The theca {fig. 5.) is not a seed, 



