APOGAMY AND APOSPORY 59 
it has been shown by Farmer and Miss Digby that there is apogamy 
as well as apospory. The cytological investigation shows that in those 
cases where sporophytes were borne on the apogamous prothalli there is 
not any migration of nuclei from one prothallial cell to another, such 
as has been described for some cases of apogamy; nor is there doubling 
of the chromosomes in any other way. In fact, the chromosome-number 
is the same for the sporophyte as for the prothallus which bears it. 
Investigation of the aposporous transition from the leaf to the prothallus 
showed also that no change of number marks the passage from sporo- 
phyte to gametophyte. There is here a case of cytological uniformity 
throughout the whole cycle, with chromosome-number about’ 90. This is 
approximately the number found in the diploid stage of a typical Athyrium 
Jjilix-foemina. The condition of the variety is as though reduction had 
been omitted from the cycle: as a consequence the prothallus being 
itself diploid, fertilisation would be unnecessary to produce a new 
sporophyte: accordingly apogamous budding will suffice, and that is what 
actually occurs. : 
A near parallel to this has been worked out with similar exactitude by 
Strasburger in Marsilia Drummondit, A.Br.1 The typical chromosome- 
numbers aré 16 and 32 respectively for gametophyte and sporophyte, 
and normal plants show the usual succession of events. But on ger. 
mination of the megaspores borne by certain plants, the gametophyte 
was found to have the diploid character, and this was seen even 
in the division to form the ventral-canal-cell: thus the ovum itself is 
diploid. In such archegonia the neck does not open, so that fertilisation 
by spermatozoids is impossible: the unfertilised diploid egg develops 
apogamously into an embryo, which is naturally diploid also. An 
examination of the sporangia showed further that while in typical A/arsi/ias 
the reduction to 16 chromosomes takes place as usual in the spore-. 
mother-cells, in J. Drummondii the megasporangia show two types of 
spore-mother-cells: the one type is normal in number, and shows 
reduction: the other type is produced in smaller numbers in the sporangia, 
for instance only four in place of the usual 16: these on division 
have diploid nuclei, and the interesting fact is that their diploid state 
does not divert them from the usual characters of form and structure. 
Since the apogamous plants produce both diploid and haploid spore- 
mother-cells, it is accordingly not surprising that both apogamous and 
sexual plants should be produced from their sporocarps: and it is apparent 
that among the representatives of the species there will be individual 
cycles completed without any change of chromosome-number : certain 
cycles will accordingly be diploid throughout. In this they correspond to 
what is seen in Athyrium filix-foemina, vax. clartssima, Jones, though 
they differ in the detail that the diploid ovum here forms the embryo, 
while in the Athyr7um the embryo arises from the prothallus by apogamous 
1 Flora, 1907, p. 123, etc. 
