1 86 Farmer and Digby. — Studies in Apospory and 
with its embryo arising from the oosphere, is plainly nearer the type than is 
either clarissima , Jones, or unco-glomeratum , Stansfield, in which it arises 
from the vegetative parts of the prothallium. 
It is furthermore of special interest to find that the same sequence 
is shown by a comparison between the cells of the first leaves of the sporo- 
phyte generation, taking the epidermal cells as the basis of measurement. 
We selected these because there was less likelihood of the introduction 
of error, since the uninjured leaf can be used. Sections introduced so 
many complications as to render any estimations based on them almost 
valueless. 
It would be doubtless going too far to suggest that these varieties 
of the Lady Fern should be regarded as of specific rank. The fact that the 
offspring are to some extent variable and unstable would alone render such 
a course undesirable. But they may perhaps be justly considered as 
4 mutations ’ which possess the faculty of continuing to vary, and even 
apparently of reverting to the parent form. It remains, however, to be 
seen whether these apparent reversions are really to be so regarded, and an 
attitude of caution respecting them is desirable, at any rate for the present. 
We propose to investigate the progeny of the forms here studied in the im- 
mediate future, in the hope of deciding some of the questions here suggested. 
The forms of Lastrea- are less regular in their divergence from the parent 
form and from each other than are those of Athyrium . In one sense, 
however, the trend of variation is in a direction opposite to that pre- 
vailing in the varieties of the latter genus, at least so far as we know them 
at present. For whereas in Athyrium the type is surpassed by its varieties 
in cell-size, &c., in the three varieties of Lastrea the reverse is the case. 
Of course a more extensive study of the varieties of each Fern may show 
that this difference is merely accidental, and that each type really stands 
more in the mean than at one end of the variations. 
Treating Lastrea pseudo-mas , and its three varieties studied by us, in the 
same manner as the former genus, the subjoined table will summarize the 
general nature of the differences. 
Lastrea 
pseudo-mas. 
Prothall ial cells of average i oo 
size (near growing-point) 
Nuclei of ditto ioo 
Epidermal cells of average ioo 
size (sporophyte) 
Antherozoids ioo 
Chromosomes : — 
gametophyte 73 
sporophyte 144 
Lastrea ps.-m. 
var. polydactyla , 
Wills. 
L^astrea ps.-m. 
var. polydactyla , 
Dadds. 
Lastrea ps.-m. 
cristata 
apospora. 
85 
70 
60 
60 
70 
75 
90 
IOO 
70 
? 
85 
90 
66 
90 
60 
132 
1 3 ° 
66? 
60 & 78 
