Notes . 
131 
cornmm , Lam., or (7. cartilagineum , Gaill. Semper thinks that the 
sponge in this case ‘ may with some probability be included in the 
family of the Chalinae/ 
GEORGE MURRAY, London. 
L. A. BOODLE, London. 
PRELIMINARY NOTE ON THE MORPHOLOGY AND 
DEVELOPMENT OP ISOETES LACUSTRIS, LINN.— The 
genus Isoetes has always been an object of interest to botanists ever 
since Hofmeister’s brilliant researches on the vascular cryptogams, 
but the accounts given by the different observers on the development 
and organogeny of the sporophyte are so conflicting, and moreover 
our knowledge of the sexual generation is so limited, that a renewed 
investigation of the whole subject seems desirable. In the present 
communication I propose to summarise, as briefly as possible, the 
more important of my own observations on one species, I. lacustris , 
to which my attention has been directed for some time past. I intend 
to deal here only with the germination of the macrospore, and to re- 
serve details of minor significance, as well as all account of the sporo- 
phyte, for treatment in a future paper, as this part of the subject 
requires critical discussion. 
The shape of each macrospore is, as is well known, that of a tetra- 
hedron with somewhat rounded sides, and the protoplasmic contents 
are enclosed in a number of coats which in mature specimens are 
differentiated into six layers. Peripherally is the episporium, a colour- 
less, glassy, and brittle layer, whose surface is beset with numerous 
irregular prominences. The episporium which is derived from the 
epiplasm of the sporangium stains with haematoxylin, though only to 
a slight extent. Within this outer layer is the exosporium, consisting 
of three brown cuticularised layers, but of which the two outer ones are 
frequently not easily distinguishable as separate coats. The two inner- 
most membranes are cellulosic in character and form the endosporium. 
The protoplasm which is contained in the spore includes a large 
quantity of reserve-material consisting of starch and oil, the latter 
being, however, eliminated during the process of soaking in turpentine 
to which the spores are subjected previously to their being embedded 
in paraffin. A number of sections through each spore were obtained 
by means of the Cambridge rocking microtome, and were arranged in 
series, thus permitting of an examination of the internal structure of 
K 2 
