194 Mr J. Scott on the Sexuality of the Higher Cryptogams. 



render the occurrence of hybrids, in the true ferns, much 

 less probable, I believe, than in any other order of Crypto- 

 gams. The Botrychiums and Ophioglossums, as shown by 

 Hofmeister and Mettenius, afford much higher facilities for 

 successful casual hybridization than occurs in the true ferns. 

 Inasmuch as in the former the antheridial and archegonial 

 cells occur on opposite sides of the prothalli, so that an 

 equal, or even higher facility, is thus afforded for the con 

 junction of distinct individuals than the pure hermaphro- 

 dite conjunctions. In the latter — or true ferns — on tlie 

 other hand, where the antheridial and archegonial cells are 

 produced upon the same side of the prothallus, and this 

 being the under, an examination of the individual relations 

 of the prothalli in a single pot wall, I think, suffice to show 

 that the crossing of distinct individuals must here be a most 

 exceptional occurrence ; unless, indeed — as so generally 

 occurs in the higher plants — nature has provided certain 

 external agents. 



In the Selaginellas, the only genus of the Lycopodiacese 

 whose reproductive phenomena are known,* the greatest 

 possible facilities are afforded for hybridization by the uni- 

 sexual characteristics of their spores, and their production in 

 distinct organs ; one kind of spore — microspore — producing 

 spermatozoa; the other — macrospore — producing the arche- 

 gonial cells. From these relations of the reproductive organs, 

 it might be supposed that hybrids would be easily raised 

 experimentally between different species. The only points 

 to be studied being a slight regard to systematic affinities, 

 and the relative time required for the development of the 



Hofmeister has tlie following remarks on the above point : — " The repro- 

 duction of those Lycopodiacese which bear ]3owdery spores of one kind only, is 

 still a mystery. Repeated sowings of the spores of Lycopodiam clavatum, inun- 

 datum, and Selago, have yielded me no results ; but I have lately often observed, 

 that in spores of Lycopodium Selago, which had been sown for from three to five 

 months, numerous small spherical cells had been formed, similar to the mother- 

 cells of the spermatozoa of Selaginella helvetica. I have not yet found sperma- 

 tozoa inside these vesicles. De Bary has lately discovered that the spores of 

 Lycopodium inundatim produce a body composed of a few cells, whose structure 

 is not unlike that of the arcliegonium of a fern. It is probable, from these 

 observations, that the similarly formed spores of Lycopodium, Psilotum, &c., 

 are of different sexes, and, as in Equisetum arvense, produce partly archegonia 

 and partly spermatozoa.'' — " On the Higher Cryptogams," p. 398. 



