442 *HE MICROSCOPE. 



observed, that ferns do not form buds like other plants ; but that their 

 leaves, or fronds as they are properly called, when they first appear, are 

 rolled up in a circular form, and gradually unfold, as in fig. 213. 

 Ferns have no visible flowers ; and their seeds are produced in clusters, 

 called sori, on the backs of the leaves. Each sorus contains numerous 

 thecse, and each theca encloses almost innumerable spores, and these 

 again the seeds. There are numerous kinds of fern, all remarkable for 

 some interesting peculiarity ; but which from want of space we cannot 

 here enumerate. 



The first account of the true mode of development of Ferns from 

 their spores was published in 1844, by Nageli, in a memoir entitled 

 Moving Spiral Fila/ments {spermMic fila/ments) in Ferns, wherein he 

 announced the existence of the bodies now called amtheridia ; but, mis- 

 taking the archegonia for modified forms of the antfieridia, he was led 

 away from a minute investigation of them. If he had followed the 

 development of the prothallia further, he would have detected the rela- 

 tions of the nascent embryo, which would probably have put him on 

 the right track. As it was, the remarkable discovery of the moving 

 spiral filaments occupied all his attention, and caused him to fall into 

 an error in certain important respects ; for example, he has represented 

 what is undoubtedly an a/rchegonium filled with cellules, sperm-cells^ 

 which, he states, " emerged from it as from the antheridia." This is 

 undoubtedly incorrect. 



With regard to the spermatozoids, his description is imperfect, the 

 only indication of the existence of cilia being a statement that he 

 occasionally saw a long filiform appendage, like that represented by 

 Meyen in the spermatozoids of Ghwra. On the other hand, the mathe- 

 matical definition of the movements of the spermMozoids is surely mis- 

 placed, since nothing can be more arbitrary or irregular than their course. 



These observations on the Ferns have acquired vastly-increased 

 interest from the subsequent investigations of Hofmeister, Mettenius, 

 and Suminski, on the allied Cryptogams, and above all, from Hof- 

 meister's observations on the processes occurring in the impregnation 

 of the Conifers. Not only have these investigations given us a satis- 

 factory interpretation of the archegonia and antheridia of the Mosses 

 and Liverworts, but they have made known and co-ordinated the exist- 

 ence of analogous phenomena in the Equisetacese, Lycopodiacese, and 

 Ehizocarpese, and shown, moreover, that the bodies described by 

 Mr. Brown in the Conifers, under the name of "corpuscles," are 

 analogous to the archegonia of the Cryptogams; so that a link is 

 hereby formed between these groups and the higher flowering plants. 



