VOLUME XXIx : NUMBER 4 
BOTANICAL: GAZE 
APRIL, 1900 
THE STRUCTURE AND DEVELOPMENT OF THE 
SPOROPHYLLS AND SPORANGIA OF ISOETES. 
CONTRIBUTION FROM THE HULL BOTANICAL LABORATORY. 
R. WILSON SMITH. 
(WITH PLATES XIII-XX) 
Few plants have excited more interest than Isoetes, a small 
genus of about fifty species, which has been variously classified, 
and the histology and development of which have been described 
in the most contradictory manner. It was with the purpose of 
obtaining, if possible, some data by which to clear up its homol- 
ogies and relationships, and especially of examining the founda- 
tion of a claim made in recent years of its being the point of 
contact between monocotyledons and vascular cryptogams that 
the following investigation was undertaken. . 
The intention at first was to have the work include not only the 
reproductive parts of the sporophyte, but also the development 
of the female gametophyte and of the embryo. But so small a 
Proportion of the spores was found capable of germination that 
the study of the prothallium had to be abandoned; and my 
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