306 Mr. J. B. Farmer. [Jan. 31, 



January 31, 1889. 

 Professor G. G. STOKES, D.C.L., President, in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Paper was read : 



I. l< On Isoetes lacustris, Linn." By J. BRETLAND FARMER, B.A., 

 F.L.S. Communicated by Professor S. H. VINES, F.R.S. 

 Received January 22, 1889. 



The genus Isoetes has 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 organogeiiy 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 plant my attention has been directed for some time past. 1 

 intend to deal here only with the germination of the macrospore, and 

 to reserve details of minor significance, as well as all account of the 

 sporophyte, for treatment in a future paper, as this part of tbe 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 haBmatoxylin, 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 

 innermost membranes of all, are cellulose 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 turpen- 

 tine, to which the spores are subjected previously to their being 



