334 Dr. E. Strasburger on Fertilization in Ferns. 



with water, the contents of the canal swell visibly, and a 

 number of vacuoles appear in the internal granular mass. 

 The distention increases ; and at the apex, where the wedge- 

 shaped mass was collected, the pressure becomes considerable : 

 the free space in the canal is thus enlarged, and at last the 

 upper cells of the neck can no longer resist; they part at the 

 angles of contact, and the mucus is ejected with considerable 

 force. The opening of the canal of the neck occurs at two 

 periods : at first the mucus, which is massed at the summit, is 

 poured out, either at once or at short intervals ; then a period 

 of rest occurs, after which the mass collected in the central 

 cell is ejected altogether. The mucus is voided with sufficient 

 force to remove any foreign bodies that may lie before the 

 mouth of the canal, and thus to clear its orifice. The granular 

 inner mucus is thus deposited at some little distance from the 

 mouth of the archegonium ; the outer, highly refractive mucus, 

 on the other hand, which lined the Avails of the canal, diffuses 

 itself in the water in lines radiating from its mouth. After 

 this evacuation the naked germ-sphere remains in the central 

 cell ; it assumes a globose form ; and a transparent spot may, 

 under favourable circumstances, be seen at its summit just 

 above the nucleus, which may be denominated the germ-spot. 

 The germ-sphere is now ready for fertilization. 



Dr. Strasburger has been able to follow this process in all 

 its details. In Pteris the opening of the canal and the entrance 

 of the spermatozoids can be readily seen ; but Cei-atopteris 

 exhibits in the clearest manner the proceedings of these bodies 

 within the central cell, owing to the transparency of its pro- 

 thallium. After the canal was opened, the spermatozoids, 

 which had previously passed by it with the same indifference 

 that they exhibited towards other bodies, showed a remarkable 

 behaviour. When they reached the mucus before the canal, 

 their movements became slower ; they were evidently detained 

 there, and their motion stopped, by an opposing medium : 

 several remained fast in the mucus ; others succeeded in freeing 

 ing themselves and hastened away. But generally the course 

 of the spermatozoid was so directed by the mucus radiating 

 from the mouth of the canal that it steered head foremost for 

 that aperture. One is not to imagine, however, that there 

 was any diffusing stream or whirlpool, seizing on the sperma- 

 tozoid and drawing it towards the orifice ; for small granules 

 remained perfectly quiescent in that position. The movement 

 of the spermatozoid within the mucus then became slower ; it 

 did not cease to revolve on its axis, but the mucus directed it 

 to the canal ; so that its operation there may be compared to 

 the action of the stigmatic juice, or of the tela conductrix 



