312 R. C. McLean. 
from the portions of other plant-tissues occurring in the sam e 
preparation. 
In general outline this specimen shows a median section of oval 
form across a thick-walled megaspore which has dehisced, the gap 
opened by the dehiscence being filled by a large pad or cushion of 
parenchymatous tissue, which also projects considerably toward 
the exterior. This pad is considered to represent the prothallus 
belonging to the megaspore. 
In the lower right-hand corner of the prothallus appear 
vesicles larger than the others. These are the supposed arche- 
gonia. 
The section passes vertically through the spore to which 
belongs the prothallus in question, and, so far as can be judged, is 
almost median, the spore-walls being thus presented in true 
transverse section. 
The spore-coat has dehisced, and the slit thus opened at the 
summit of the spore has been considerably widened by the 
expansion of the prothallus, so that a wide mouth is left, which is 
bridged by the ventral surface of the prothallus. 
The spore-coat itself, although thick, is not of cellular compo¬ 
sition, but is, in general, absolutely compact and opaque, being 
constructed of black, granular matter. 
Borne upon its exterior, forming an equatorial belt, are 
numerous slightly-branched appendages, of the same dark colour 
as the spore-wall, and apparently of substance continuous with it. 
These appendages are short, being but little longer than the thick¬ 
ness of the spore-wall, and seem to have been invested by a 
dark membrane, which appears in longitudinal section on each 
side of several of them. 
Appendages of the same kind, which are well known from many 
spores of similar character, occur in different forms and diversely 
distributed. They were originally described by Reinsch 1 as 
parasites of the spores, which latter he considered to be individual 
organisms, naming the supposed genus Triletes ; the appendages 
he placed in a genus Tricliostelium , belonging to a group called 
Stelidese. There seems little reason to believe that this view is 
other than fantastic. 
Apart from the equatorial belt, the exterior of the spore-coat 
is smooth ; and the coat is of even thickness, save where there is 
' Reinsch, J. P. “ Micro-Palaso-Phytologia Formationis 
Carboniferae,” 1884. 
