l 75 
Apogamy in Ferns. 
and by the direct outgrowth of the sporophyte from the gametophyte. 
But in the variety Drummondae the sporophyte develops from the 
oosphere, and there is no cylindrical process. In the second place there 
is a very important difference between the behaviour of the nuclei of the 
prothallial cells in the two cases. In the aposporous prothallia of our 
variety there is neither nuclear migration nor fusion, but Lang describes 
and figures cells containing two nuclei as being situated £ near the border 
line between sporophytic and prothallus tissue/ We regard this as of 
paramount importance taken in connexion with the fact that whereas our 
prothallia were produced aposporously, those with which Lang was working 
had been grown from spores. It may therefore be taken as certain that 
whilst our prothallial nuclei, as regards the number of their chromosomes, 
are identical with the nuclei of the sporophyte, those of Lang’s prothallium 
only possessed half the number characteristic of the sporophyte. Hence 
the nuclear migration (and probable fusion) in this case would fall exactly 
in a line with what we shall describe for Lastrea pseudo-mas vars. poly - 
dactyla, Wills and Dadds (see p. 176). 
The results obtained from the study of this Fern may be summarized 
as follows:— 
1. Aposporous development of the prothallia occurs on the margin of 
the leaf. 
3 . There is no reduction of the chromosomes on passing from the 
sporophyte to the gametophyte. 
3. Whereas the ordinary Hart’s-tongue Fern possesses 6 4 (premeiotic) 
and 32 (postmeiotic) chromosomes in the sporophyte and gametophyte re- 
spectively, the variety crispum Drummondae exhibits some amount of 
variation, and contains from 80 to 100 chromosomes in its nuclei. 
4. There is no migration or fusion of nuclei in the cells of the prothallium 
of this variety. 
5. The embryo arises apogamously from the unfertilized oosphere. 
6. The oospheres may become enclosed each in a membrane before 
the archegonial neck opens. 
5. Lastrea pseudo-mas var. poly dactyla, Wills. 
This Fern has long been recognized as one which only produces 
apogamous embryos on the prothallia, which are nevertheless raised from 
the ordinary spores. In 1903 we published a preliminary statement of 
the cytological observations we had made on the plant. 1 These observa- 
tions not unnaturally were received with some degree of scepticism, but 
our further investigations have convinced us of the accuracy of our state- 
ments, and they have at the same time served, as we think, to invalidate 
1 Farmer, Moore and Digby, loc. cit. 
