262 Linnaan Society. 



which give the appearance just mentioned either lying on its exter- 

 nal surface or forming that portion of it which lies heneath the valves. 

 From the appearances and impossibility of separating the cells from 

 the membrane I am inclined to believe that the cavity formed by this 

 membrane is completed by the cells, or, in other words, that the 

 sac is partly membranous and partly cellular. It is possible that 

 this last described membrane may exist before germination begins, 

 notwithstanding the numerous unsuccessful dissections which I 

 have made to discover it, the failure being owing to its extreme de- 

 licacy ; but I am pretty well satisfied that it is a product of germi- 

 nation, because I have not the slightest difficulty in demonstrating 

 it after that has commenced, nor is there the slightest trace of it in 

 any stage of the development of the sporule. However this may be, it 

 is quite certain that fresh cells are gradually formed on the external 

 surface of the cellular part of the sac, and that the valves of the 

 third membrane are very, soon ruptured and gradually turned back 

 by the growth and protrusion of this button-like cellular germ. 

 The enlarging cellular mass then distends the conical projection, 

 unfolding the plicae of that body^, and at length appears externally, 

 with four of its cells projecting beyond the general mass and com- 

 pressed into a quadrangular form, I fancy by the pressure of the apex 

 of the cone, the aperture in which is quadrangular. These projecting 

 cells soon harden and acquire a reddish brown hue, and in the ad- 

 vanced stage of germination appear like a brown quadrangular space, 

 which I should have little hesitation in referring to the above cause 

 did I not find several similar spaces on the germinating sporules of 

 Isoetes lacustris, which I could not refer to such an origin : it must 

 be observed however that I have not seen the earlier stages of germi- 

 nation in Isoetes. Soon after the exposure of the entire germ, which 

 is effected by the reflexion of the valves and conical membrane over 

 the side of the sporule, where they lie quite concealed by the germ, 

 little fibrillee or rootlets begin to shoot from one side. They are 

 simply articulated tubes or elongated cells applied end to end with 

 frequently a bulbous extremity, and each is produced from one of 

 the cells of the germ. They differ much in length in diflferent 

 sporules ; in some they are not longer than the sporule, whilst in 

 others they are three or four times that length, and, in common with 

 the cells of the germ, contain granules which in these are colourless 

 but in the germ green. The cluster-like appearance of the cells 

 which form the germ, soon after the appearance of these fibrillae be- 

 gin to change, the cells becoming flatter and more intimately con- 

 nected with each other. At the same time an internal change is taking 



