THE HIGHER CRYPTOGAMIA. 199 



cells. This process is the first visible effect of impregna- 

 tion ; in abortive archegonia the canal remains open. Tn 

 the latter the walls of the canal throughout, and also those 

 of the central cell, assume a deep brown colour. In im- 

 pregnated archegonia this colour only extends downwards 

 over that part of the canal which is not closed. Immedi- 

 ately after the closing of the lower end of the canal, and 

 during the progress of active multiplication in the cells 

 adjoining the embryo-sac, the impregnated germinal vesicle 

 attains the size of the sac. Even before it arrives at this 

 stage two secondary nuclei usually appear in its interior in 

 the place of the primary one which has disappeared (PL 

 XXVI, fig. 5). The first septum by which the germinal 

 vesicle is divided, is not however formed until the latter 

 has entirely filled the embryo-sac. This septum stands at 

 right angles to the longitudinal axis of the prothallium, and 

 almost perpendicular to its surface. It diverges from a 

 perpendicular erected upon that surface, downwards and 

 forwards towards the indentation of the prothallium {a, b 

 in PI. XXVIII, figs. \\ 3 5 ; PL XXVII, figs. 6 \ 7 b ). 

 Soon afterwards an oblique septum is formed in each of 

 the two cells into which the germinal vesicle is divided ; 



attraction and condensation will yield abundance of moisture to the prothallia. 

 After one or two hours the surfaces of the larger prothallia, which are covered 

 with archegonia, are found almost covered with spermatozoa, partly in motion 

 and partly at rest. If a delicate longitudinal section through the parenchyma 

 of these prothallia be examined immediately, with a magnifying power of from 

 200 to 300 diameters, spermatozoa are sometimes found in all the archegonia 

 along the whole length of the section. I thus found three spermatozoon in 

 active motion in the central cell of the archegonium of Aspiclium filix-mas. In 

 this case the motion ceased seven minutes after the commencement of the 

 observation, and was accompanied (probably caused) by the coagulation of the 

 albuminous matter of the cell-contents. In the same fern on two occasions, and 

 also in Gymnogramma calomelanos and Pteris aquilina, I have seen a spermatozoon 

 in motion in the central cell of the archegonium ; and in the above-mentioned 

 species, and also in Asplenmm septeririonale, and filix-feviina, I have seen a 

 motionless body near the germinal vesicle (after the growth of the latter has 

 commenced) answering in form to a spermatozoon. Lastly, in Aspiclium filix- 

 mas and Pteris aquilina, I have often seen motile spermatozoa in the canal of 

 the opened archegonia, the motion of which spermatozoa ceased during the 

 continuance of my observation. I may add that these observations were very 

 numerous, and were undertaken with the view of following out the cell 

 development of the embryo. In a single prothallium, cultivated in the manner 

 stated above, and laid open longitudinally as I have mentioned, there will not be 

 found more than three, or at the most, four archegonia open at the apex; 

 spermatozoa will probably be found in not more than one in thirty of such 

 archegonia, and they will often not be found at all, 



