68 PKOCEEDINGS OF THE AMERICAN ACADEMY 



IV. 



AN ASEXUAL GROWTH FROM THE PROTHALLUS OF 



PTERIS SERRULATA. 



By William G. Farlow, M.D. 

 Read, Jan. 28, 1874. 



While studying the development of the archegonium in the Polypo- 

 diace«, a few weeks ago, in the botanical laboratory of the University 

 of Strasburg, a peculiarity was first noticed in the prothallus of Pteris 

 serrulata which seems to have an important bearing on the question of 

 the fern prothallus in general. 



The material used was taken from a pot in which Pteris serrulata 

 and Aspidium molle had been sown. At the beginning of the investi- 

 gation there were a number of seedlings of both the above-named 

 species which were considerably advanced in growth ; and in addition 

 there were numerous prothalli, from some of which young plants 

 had begun to grow, and others still younger on which no incipient 

 plantlets could be discovered with the naked eye. A search was 

 made among the latter for prothalli in a condition suitable to demon- 

 strate the earliest stages of growth after the fertilization of the arche- 

 gonium. Some of these prothalli were normally developed, having 

 both antheridia and archegonia, from which occasionally an embryonal 

 growth was seen. During the search, however, numerous specimens 

 were found presenting the anomaly of scalariform ducts in the sub- 

 stance of the- 2:)rothallus ; and such prothalli, when still further devel- 

 oped, showed that the young fern-jjlautlets produced by them were the 

 result of a direct budding of the cells, and not of the changes caused by 

 the act of fertilization in a single embryonal cell. The number of 

 cases in which the above-mentioned peculiarity was manifested was 

 about fifty ; but, undoubtedly, the actual number was greater, inasmuch 

 as some of the young fern-plantlets in the pot, which were too old to 

 allow one to say whether they were of the regularly developed (that 

 is, by growth of an embryo) or not, probably belonged to the number 

 of those developed by direct budding. The shape of the prothalli was, 

 as usual, more or less obcordate ; and those in which the anomaly 

 presented itself, although variable in outline, were narrower than the 



