Spore-Formation in Leptosporangiate Ferns 1 . 
BY 
R. P. GREGORY, B.A., 
St.John's College , Cambridge. 
With Plate XXXI and a Figure in the Text. 
P REVIOUS accounts of the formation of the spores in Ferns differ from 
one another as regards essential features ; so that an independent 
examination was undertaken as a preliminary to work upon the nuclei 
of the gametophyte generation. 
The investigation recently made by Farmer and Moore 2 into the 
reduction-phenomena of certain plants and animals led to a new inter- 
pretation of the processes undergone in the formation of the chromosomes at 
the heterotype division, indicating the occurrence of a transverse fission 
of the chromosomes at that division. A more extended examination of the 
Leptosporangiate Ferns was therefore made, with results which I think 
leave no doubt that the essential features of the phenomena described by 
Farmer and Moore occur throughout this group of plants. 
The species which I have examined are Pteris tremula , Scolopendrium 
vulgar e, Asplenium marinum , the so-called hybrid between Scolopendrium 
vidgare and Asplenium Ceterach , O node a sensibilis % Davallia capense , 
Fadyenia prolifer a (all included among the Polypodiaceae) ; Alsophila 
excelsa and Dicksonia davallioides (Cyatheaceae). The processes of spore- 
formation are exactly similar in all these types, except as regards the 
number of chromosomes present 3 . 
i. Earlier Work upon Spore-Formation in Ferns. 
Calkins 4 , working upon Pteris tremula and Adiantum cuneatum , 
described a process of tetrad (‘ Vierergruppen ’) formation at the heterotype 
division, very similar to that observed in various animals by several 
authors 5 . From this he drew the conclusion that a transverse division of 
the chromosomes, involving a qualitative reduction, took place in the Ferns. 
1 An early account of the results given here appeared in the Roy. Soc. Proc. vol. lxxiii. p. 86 
(Feb. 4, 1904). 
2 Farmer and Moore, ’03. 3 See p. 447. 
4 Calkins, '97. 5 See Wilson, ’02, p. 246 et seq. 
[Annals of Botany, Vol. XVIII. No. LXXI. July, 1904.3 
