Developments of the Oophyte in Trichomanes . 281 
later that these are characteristic reproductive organs of the 
oophyte, and their presence serves to strengthen the conclusion 
that in these strap-shaped growths from the margin or tip of 
the pinnule we have to deal with prothalloid developments 
produced in an aposporous manner. 
But it is not only the marginal cells of the frond which may 
give rise to protonemal filaments ; it appears also that any 
marginal cell of one of the ribbon-shaped prothalli may do the 
same : this is shown in Figs. 32, 33. Between the filamentous 
(protonemal) and flattened (prothalloid) forms intermediate 
steps may be found : thus, in Fig. 31 is shown a growth from a 
single marginal cell of the frond, which passes over almost at 
once into a narrow flattened ribbon ; again, in Fig. 30, the right- 
hand branch consists of only two rows of cells, and this may 
be compared with Fig. 35, which is in part of its length a 
simple filament, but two of the cells have divided longi- 
tudinally, so as to show a transition to the flattened form. In 
face of these examples, which are only a few from the many 
observed, it is clear that there is little or no regularity of form 
or of place of origin in these prothalli, and that no sharp limit 
exists between the simple protonemal filament and the flattened 
expansion. 
Passing on now to further details, the typical protonemal 
filament consists of a simple row of cells of variable length 
(Figs. 27, 34) ; the septa dividing them are transverse, or very 
slightly inclined, and show a striated appearance in optical 
section. In some filaments each cell may produce one 
lateral outgrowth with considerable regularity (Fig. 34) ; occa- 
sionally more than one may arise from each cell ; or such 
appendages may be absent from a considerable proportion of 
the cells. These growths may develop in different ways : the 
large majority of them may remain of small size, and, turning 
brown, acquire the character of rhizoids (Figs. 33, 34) ; or 
they may repeat the characters of the parent filament as pro- 
tonemal branches (Fig. 33 p) ; or again, they may develop 
at once as flattened expansions (Fig. 34 x). The cells of the 
protonema are crowded with chlorophyll-corpuscles, and each 
