Developments of the Oophyte in Trichomanes. 273 
longitudinal sections be cut traversing the placenta, it will 
be seen that towards the base of the sorus the sporangia are 
of smaller size, many of those lowest down showing various 
degrees of arrest, corresponding to their basipetal order of 
development. As the frond grows old, these may resume 
activity of growth, which, however, does not result in the 
formation of normal sporangia with spores, but of irregular 
masses of tissue, which differ widely in appearance from 
normal sporangia (Figs. 2, 3, 4). These irregular masses may 
then produce, by direct vegetative outgrowth, rhizoids, r, 
similar in appearance to those of the normal protonemal pro- 
thallus, and finally a filamentous protonema. Growths simi- 
lar in nature, though often extremely irregular in form, may 
arise from the tissue of the placenta itself (Figs. 5, 6). In old 
fronds, where the general mass of the placenta has lost its 
activity, and turned brown, these growths are easily dis- 
tinguished by their colour. It is thus seen that in Tr. pyxidi - 
ferum irregular initial growths, derived by direct vegetative 
outgrowth of the tissues of the sporophyte, may form the 
starting-point for the production of the protonemal oophyte ; 
in fact, there may be traced a transition from the one gener- 
ation to the other by a purely vegetative process, without 
the intervention of spores. This has elsewhere been termed 
the process of apospory , and it is here again, as in the ex- 
amples previously described, associated with a partial sporal 
arrest x . It is to be regarded as a possibility that in other 
cases where a germination of the spores within the sporangium 
or sorus has been described, more careful investigation may 
disclose a similar aposporous development 
A Doubtful Vegetative Production. — In various other species 
of Trichomanes a vegetative multiplication of the oophyte by 
means of gemmae has been described 1 2 . Although I have 
examined a very large number of specimens of the protonema 
1 Compare Bower, on Apospory and Allied Phenomena, in Linn. Trans. Vol. ii. 
Part 14, p. 302, & c. 
2 Mettenius, 1 . c. Taf. v. ; Cramer, 1 . c. ; Goebel, 1 . c. p. 95 ; also a preliminary 
note by Bower on Tr. alatum in Annals of Botany, Vol. i. No. II (1887). 
