412 PROPAGATION OF THE SPECIES. CHAP. IX. 



nera Blasia and Riccia, are also, according to 

 Gaertner, propagated only by gems ; while Mar~ 

 chantia, Anthoceros, Jungermannia, and Lycoper- 

 don are said to be propagated both by gems and 

 seeds. 

 Challenge s uc h j s the sum of the theory of Gaertner, who 



of Gaert- 

 ner. adds If it be said that these granules are not gems 



but seeds, let it be proved that they have the usual 

 integuments of seeds : and if it be said that they are 

 exceptions to the general rule, and are seeds though 

 destitute of the usual integuments, let it be proved 

 that the plants producing them are furnished with 

 sexual organs. 



Accepted The challenge thus held out to the Cryptogamist 

 a has been accepted by M. Corrca de Serra,* at least 

 with regard to the proscribed genera of submersed 

 Alga ; which he has endeavoured to restore to the 

 rank of seed-bearing plants. The true Fuel were 

 admitted by Gaertner to produce perfect seed, 

 though only upon the Adansonian notion of vege- 

 table Aphroditism ; but the Ceramiums, together 

 with the Ulva and Conferva were regarded as 

 producing gems merely, and on the following 

 grounds : 



1. Because in the Ceramiums and Ulv& the 

 grains are solitary, are not contained in a proper 

 uterus, and are consequently without a placentation, 



'2. Because in germinating they leave no coat 

 behind. 



* Phil. Trans. 1796. 



