HOFMEISTER 117 



Gymnosperms also, and demonstrated that in all of them 

 there was an alternation of a sexual with an asexual 

 generation, each starting from a single cell. These results 

 were published between 1849 and 185 1 under the title 

 Vergleichende Unterstichungen hoherer Kryptogamen, a 

 treatise which was translated into EngUsh in 1862, at the 

 instance of the Ray Society, and also in 1852 as Beitrdge 

 zur Kenntis der Gefdsskryptogamen, etc., while several 

 genera were dealt with individually at later dates, such 

 as Riella in 1854 and Salvinia in 1857. 



It is quite impossible to give you any adequate idea 

 of the contents of these and other researches pubUshed by 

 Hofmeister during the decade 1849-59, but when I tell you 

 that in them we are presented with detailed accounts of the 

 anatomy and hfe cycles of many Bryophyta and also of the 

 chief genera of Pteridophyta, such as Pilularia, Salvinia, 

 Isoetes, Ophioglossum, Equisetum, and Selaginella, 

 together with comparisons of these and other genera with 

 Coniferae and Angiosperms, you will readily recognise 

 that Hofmeister's work was, in the true sense of the 

 term, epoch-making. As I have already said, Hofmeister 

 showed that alternation of a sexual with an asexual 

 generation was common to all the plants usually spoken 

 of as Mosses and Vascular Cryptogams, and further that 

 these two phases could be recognised in Gymnosperms 

 and Angiosperms as well. In the Ferns the spore gave 

 rise to an inconspicuous, green, parenchymatous plant, 

 the prothallus, on which archegonia and antheridia were 

 produced, and the fertihsed ovum in turn developed into 

 the fern plant, or sporophyte, producing spores once 

 more and thus completing the cycle. In Mosses the 

 spore developed into a much more highly differentiated 

 gametophyte with stem and leaves, or structures that at 

 least corresponded to these organs ; but in this case the 

 fertihsed ovum did not become an independent plant 

 but a semi-parasitic sporocarp or sporogonium, whence 

 in turn spores were derived. 



