FERN GENERATION, NORMAL AND ABNORMAL. 



251 



thorough exponent as was Count Suminski, and when we reflect 

 that these drawings were published more than half a century 

 ago, when the facilities for such investigation were certainly less 

 than at present, our admiration must be increased. 



The normal mode of fern-generation has now, I think, been 

 fairly illustrated, and chronologically we come next to Professor 

 Farlow's discovery in 1874 of the first found abnormal method, 

 called apogamy, because it shortened the life cycle by the 

 reproduction of the fern from a simple non-fertilised bud which 

 formed upon the prothallus in precisely the same spot as the 

 normally fertilised ovules occupy. Pteris cretica was the fern 

 upon which this discovery was made, and on further investiga- 

 tion it was found to do this constantly and not exceptionally. 

 Professor de Bary followed this up and found that our familiar 

 crested form of male fern (Lastrea pscudo-mas cristata) did 

 precisely the same thing, no archegonia being formed on any of 

 the prothalli examined, so that all the young plants were 

 asexually produced. The normal form of the same species pro- 

 duced in his cultures normal plants, but L. Kny has recently 

 found that it also produces apogamously in some instances. 



In all cases of apogamy recorded, with one exception, the 

 young plants arise precisely as if engendered in the usual way, 

 and their true genesis can only be verified by previous microscopic 

 examination, when a small dark spot is seen instead of the 

 thickened cushion bearing the archegonia, which as appendages 

 to the ovaries are formed on the under side of the prothallus, as 

 already mentioned. The first fronds are also identical in form 

 with normal ones. The single exception occurs in the case of a 

 prothallus now figured on the screen, which arose in one of my 

 own sowings of Athyrium filix famina. This, after attaining 

 an abnormally large size, quite half an inch across, remained 

 dormant for several months. It then commenced to develop 

 two horns, as figured, upon each of which, and far away, as will 

 he seen, from the archegonial site, an ordinary bud appeared. 

 Both these buds grew as large as pins' heads, and eventually 

 developed fronds of some size, the first bearing no less than ten 

 pair of pinnae. In this case, it will be seen, the apogamic 

 character is accentuated by the distance from the usual genera- 

 tive point on the under side of the prothallus, and it is further 

 differentiated by the previous formation of a bulbil (Farlow's 



