318 NOTES AND MEMORANDA. 



It was tlicn shown that, in some cases, the prothalli of Pteris cretica, 

 instead of the usual growth from a fertilized archegonium-cell, pro- 

 duced ordinary buds, from which the new fern plant developed without 

 any sexual action whatever. The observations now published by Da 

 Bary were made with the intention of ascertaining more in detail the 

 frequency with which the non-sexual mode of reproduction occurred 

 in ferns, and its relation to similar processes in other groups of the 

 vegetable kingdom. 



He found, on sowing the sj)ores of Pteris cretica, obtained both from 

 ciiltivated jilants of that species and from forms which grew wild in 

 Italy, that, in all cases, the prothalli produced only the non-sexual 

 buds, to which he gives the name of " Farlowsche Sprossung." In the 

 few cases where antheridia, archegonia, and the normal embryonic 

 development ajiparently occurred, he found, by watching the further 

 development of the fern, that the prothalli were not those of Pteris 

 cretica, but came from the spores of other species which had acci- 

 dentally found their way into the cultures. Of the ditferent species 

 studied by De Bary, in thirty-four, exclusive of varieties, only the 

 normal development by embryo-formation in the central cell of the 

 archegonium was observed ; in three, Aspidium Filixmas var. cristafum., 

 Aspidium falcatum, and Pteris cretica, only the non-sexual budding. 

 The prothalli of Pteris cretica may or may not bear antheridia. When 

 present, they have the same structure as in the typical PolypodiacecB. 

 In by far the majority of cases there are no traces of archegonia, even 

 in a rudimentary condition. Out of hundreds of cases, only seven 

 were found with archegonia, and they all aborted. Aspidium Filix- 

 mas perfectly resembles Pteris cretica in the distribution of antheridia 

 and archegonia, but in Aspidium falcatum archegonia occurred in at 

 least 25 or 30 per cent, of the prothalli. Although in the cases 

 observed they had all aborted, De Bary thinks it possible that cases 

 may occur in which the normal embryo-formation takes place, which 

 is hardly possible in the two species first named. 



The budding process, in all three cases, consists in the formation 

 of a protuberance on the under surface of the prothallus, from which 

 grow a first leaf, root, and stem-bud as in the normal embryo-formation, 

 although their relative position and date of development vary. The 

 protuberance is generally found just at the back of the sinus, where 

 the fertilized archegonium normally occurs. Variations were seen in 

 which the first leaf grew from the upper surface of the prothallus, 

 and, at times, two leaves were produced, one on the upper and one on 

 the lower surface. Secondary forms may be produced upon elon- 

 gations of the lateral lobes of the prothallus. Some of the more 

 l^eculiar forms are figiired in the plate which accompanies the article. 

 In the three species under consideration, as the normal reproduction 

 by an embryonal growth has been lost, and another, non-sexual form 

 of reproduction has taken its place, we may infer tbat they have 

 descended from some ancestral form in which the sexual mode of 

 reproduction existed. This is illustrated by the case of Aspidium 

 Filix-mas var. cristatum, which is undoubtedly derived from the 

 typical Aspidium Filix-mas, in which only sexual reiu'oduction is 



