^70 LETTER XXIII. 



nor is it a body whose functions are of a nature similar 

 to those of the seed ; you require a pretty good mi- 

 croscope to examine it correctly, but with such an 

 instrument you will make it out to be a roundish 

 compressed body, seated on a jointed stalk, which runs 

 up one side of the theca {fig. 5. a.). Upon examin- 

 ing a good many of the thecse, you will no doubt 

 remark some of them burst open {fig. 6.) ; and then 

 you will find that they are hollow bodies, containing 

 a quantity of extremely minute oval grains {fig. 6. «.), 

 called SPORES, by Botanists. It is in the spores that 

 the power of increase resides ; every one of them 

 will form a new plant, and consequently they are 

 analogous to seeds ; but, as they do not result from 

 the action of pollen upon a stigma, they are not real 

 seeds, but only the representatives of those organs 

 amongst Flowerless plants. 



How simple is all this ; how different from every 

 thing we have seen in other plants ! and yet no 

 doubt as perfectly adapted to the multiplication 

 of Ferns as any more complete contrivance. How 

 prodigious too is the power that these plants possess 

 of disseminating themselves ! Hart's-tongue, owing 

 to its small size, is one of those in which the power 

 resides only in a small degree ; and yet a little com- 

 putation will shew even its means to be prodigious. 

 Each of its sori consists of from 3000 to 6000 thecae ; 

 let us take 4500 as the average number. Then each 

 leaf bears about 80 sori ; which makes 360,000 thecsB 

 per leaf; the thecse themselves contain about 50 

 spores ; so that a single leaf of Hart's-tongue may 



