360 XXVI. REPRODUCTION OF THE PTERIDOPHYTA. 



narrow coils bear long fine cilia. Between the posterior coils 

 lies a delicate vesicle containing granules which give the starch 

 reaction. By the addition of a little iodine the spermatozoids are 

 very beautifully fixed. Fuller investigation shows that the pos- 

 terior broader coils contain the nucleus of the spermatozoidal 

 mother-cell. 



The Archegonium. By the anterior indentation of the pro- 

 thallium, on the median cushion, we see the female sexual organs 

 the archegonia. Nearest the indentation, they are still imperfect; 

 farther in, are ripe but unopened ; still farther, perhaps dead and 

 opened, brown inside. The female -sexual organs are very easy to 

 distinguish from the male. They project above the surface of the 

 prothallium in the form of short, cylindrical structures, curved 

 away from the anterior sinus. This free portion of the arche- 

 gonium is only its neck, whilst the ventral portion is found sunk 

 in the tissue of the prothallium. In the neck we distinguish a 

 unilamellar wall, formed of four cell-rows, and a central canal, 

 the contents of which, in ripe archegonia, appear granular in the 

 central portion, and strongly refractive peripherally. This inner 

 canal, the neck-canal, broadens upwards like a club. Below, it 

 passes into the central cell of the archegonium, in which is found 

 the oosphere. This last, it is true, is scarcely distinguishable. 

 If the prothallia had been allowed to remain dry for several days 

 before the commencement of the investigation, we shall probably 

 .be successful in seeing the opening of an archegonium. We 

 choose for continuous observation an archegonium the contents 

 of the canal of which appear strongly refractive. Often the 

 opening takes place almost instantaneously ; often it is necessary 

 to wait some time. The opening of the neck is the result of the 

 pressure which the strongly refractive swelling substance of the 

 neck-canal exerts upon the wall of the neck. The four cells at 

 the apex of the neck suddenly separate from one another, and the 

 contents of the neck-canal pour out. The strongly refractive 

 substance of this diffuses as a colourless mucilage in the surround- 

 ing water, while the granular contents are gradually disorganised. 

 The evacuation of the contents takes place interruptedly ; first 

 come out the contents of the neck-canal, then those of the 

 ventral canal-cell last cut off from the oosphere. 



Fertilisation. 'Under specially-favourable conditions we may 

 now see the entrance of the spermatozoids into the archegonium. 

 The chances of this are increased if we have placed with the older 



