164 Farmer and Dighy— Studies in Apospory ' and 
in every way the statement already made in a preliminary communication 1 
to the effect that the transition from the sporophyte to the gametophyte 
in this Fern is attended by no reduction or alteration in the number of the 
chromosomes, nor is there any constant feature that would serve to dif- 
ferentiate these structures in the two generations respectively (cf. Figs. 8, 9, 
13, 14, 15). We have further compared the chromosomes of the sporophytic 
tissue (Figs 9, 23, 24) in the embryo with the young cells of older pro- 
thallia with the same result. 
It would be unsafe to predict that no case of chromosome reduction 
will ever be found to be associated with apospory, but at any rate it may 
be at once stated here that, so far as our present knowledge goes, apospory 
is always found to imply the absence of the meiotic phase from the life- 
cycle of the organism. And the natural corollary of this conclusion is that 
the embryos, when they occur on the ‘ gametophytes ’ of such plants, 
always arise apogamously, that is, they are formed without fertilization 
from cells or tissues that already possess the full complement of ‘ sporo- 
phytic ’ chromosomes which have persisted unchanged through that period 
of the life-history which is commonly termed the gametophyte. 
The cell of the sporangium that is destined to a prothallium grows out 
in a papilla and its nucleus there divides (Fig. 8). The chromosomes 
at this division have been repeatedly counted, and they are approxi- 
mately ninety. 
It will of course be readily understood by those who are familiar with 
cytological work of this kind that an exact estimation is impossible, but we 
have taken every care to get as near as possible to the real number. In 
our former communication the totals were underestimated, owing to the 
great difficulty of distinguishing the individuals. It is easier to arrive at 
most consistent results by counting the chromosomes when in diakinesis, 
i. e. just before they congregate on to the spindle. The division is 
typically premeiotic . 
The first division of the papilla most often results in the cutting off 
of a terminal cell (cf. Figs. 3, 6) that does not divide further, but forms 
a mucilage cell, whilst the more proximal cell by further divisions gives 
rise to the prothallium. It is important to note that all these mitoses are 
strictly of a premeiotic character, and no indication of a heterotype division 
is seen. A remarkable and constant character of the prothallial nuclei is 
afforded by the presence of several nucleoli often exhibiting curious forms 
(Figs. 10, 11, 12). They are quite diagnostic of the prothallia of this 
variety as distinguished from the type represented by Ath. Filix-foemina , 
and their presence affords a valuable criterion of the purity of cultures in 
the few doubtful cases that we have encountered. They are clearly ‘ chro- 
matin nucleoli,’ and their relation to the linin filament on approaching 
1 Digby, Miss L. ; loc. cit. 
