Structure & Development of Targionia hypophylla. 111 
the archegonia it surrounded were still unfertilised,” but in my prepa¬ 
rations it was found that the completion of the involucre— i.e., its 
closure, the development of the interlocking marginal teeth, and the 
other processes described below—never took place unless one or 
more of the archegonia had been fertilised and showed the early 
stages of embryogeny. Hence the development of the involucre 
Fig. 2. Targionia hypophylla. A. Median longitudinal section of plant 
with nearly mature sporogonium. B, C. Early stages in development of 
sporogonium, in longitudinal section. D. Part of suture of involucre, showing 
the interlocking tooth-like cells on the margins of the valves. E. Part of 
involucre caused to gape by pressure, showing the interlocking marginal cells. 
F. Part of section of capsule, soon after the rounding off of the spore mother- 
cells, between which are the sterile (elater-forming) cells. G. Spore-mother¬ 
cell and young elater. H. Part of section of capsule showing two fixed 
elaters. 
