On Isoetes lacustris, L. 
BY 
J. BRETLAND FARMER, M.A., F.L.S. 
Fellow of Magdalen College , Oxford. 
With Plates V and VI, and Woodcut i. 
EW genera amongst the higher series of plants have 
JL attracted more general attention and interest than that 
which has for so long been centred round Isoetes. Regarded 
as a study in taxonomic research, the numerous points of 
contact which it displays with families which are otherwise 
sharply severed from each other in affinity, are sufficient to 
justify its claims on the comparative morphologist, whilst at 
the same time the anomalous character of its structure has 
long afforded ample and fruitful material for histological in- 
vestigation. 
The object of the present paper is to attempt the elucida- 
tion of some of the numerous points of development and 
organogeny which have hitherto, in spite of the numerous 
workers in the field, baffled or escaped explanation, and also 
as far as possible to give a connected account of the oophyte 
whose development has long remained obscure, in the hope 
that further light may thereby be thrown on the difficult ques- 
tion as to the position of Isoetes in the natural system. 
Von Mohl 1 , who may be said to be almost the first person 
who investigated carefully the structure of Isoetes , drew atten- 
tion to its more important peculiarities, such as the arrange- 
1 V. Mohl, Ueber den Bau des Stammes von Isoetes lacustris, Linnsea, 1840; also 
Vermischte Schr. 
[Annals of Botany, Vol. V. No. XVII. December 1890.] 
