Johnson . — On Stenogramme interrupta. 363 
plant (Fig. 8). This ‘fertile line/ as it may be called, increases 
in distinctness as the fruits form, becomes more convex, and 
may finally become very irregularly swollen (Fig. 9). It was 
with considerable interest that I began, in the autumn of 1889, 
the microscopic examination of the nature of the fertile 
line. The ordinary sterile thallus of 5 . interrupta shows, in 
cross-section, 4-6 layers of cells, of which the inner 2-3 layers 
consist of larger cells. Where the line is, the thallus is as 
many as 12 layers thick, the internal cells being much 
smaller, more numerous, and relatively richer in contents than 
elsewhere (Fig. 10). Microscopic examination shows that, 
when the line is only just visible to the naked eye, the female 
organs or procarpia are already beginning to appear, and that 
where the line is absent the procarpia are also absent. The 
gaps in the fertile line, to which the plant owes its specific 
name, are due to the absence of procarpia or to the non- 
fertilisation of procarpia present, in different regions of the 
fertile line. By making sections through the line in different 
directions, at the right stage, the procarpia are seen to be very 
numerous, extending, in almost continuous series, along the 
whole length of the line, 3 or 4 deep, on both surfaces of the 
thallus (Fig. 10). Thus, in a fertile line an inch long, there 
must be several hundred fertilisable procarpia. Each pro- 
carpium has the more usual floridean characters, and consists 
of a curved 3-4-celled special carpogenous branch, of which 
the free terminal cell is the carpogonium, from which the tricho- 
gyne grows out in the usual way, projecting, for some distance, 
on the surface of the thallus (Fig. 11). The curvature of the 
carpogenous branch is such as to place the carpogonium near 
to the surface of the mother-cell of the branch. This mother- 
cell is a large medullary cell, well marked by its rich protoplas- 
mic contents. After the spermatium has come into contact with 
the trichogyne and fertilisation of the carpogonium has taken 
place, the trichogyne is cut off by a septum from the fertilised 
carpogonium, which becomes connected by an ooblastema- 
filament with the mother-cell of the carpogenous branch - the 
auxiliary-cell (Fig. 11). The cell, thus resulting from the 
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