XI THE HOMOSPOROUS LEPTOSPORANGIAT^ 347 



sen both speak of the quantity of starch in the axial row of 

 cells in O. regalis, but in neither O. cinnavioniea nor O. Clay- 

 toniana was this noticeable. As the egg approaches maturity 

 the nucleus becomes large and distinct, and one or two nucleoli 

 are present. The chromosomes are not conspicuous, a con- 

 dition that we have seen before is not uncommon in the ees; 

 nucleus. 



A curious appearance was noted several times just before 

 the archegonium seemed about to open, and after the formation 

 of the ventral canal cell. This was the separation from the 

 upper part of the egg of a small body containing what looked 

 like a nucleus. Whether this is something analogous to the 

 " polar body " found in animal ova could not be determined. 



When the archegonium opens, the four rows of cells bend 

 strongly outward, and frequently some of the terminal cells 

 become detached. A large receptive spot is present, and the 

 nucleus is smaller than in the younger egg, and contains more 

 chromatin, and usually but a single nucleolus. 



Fertilisation 



The horizontal position of the archegonia, as they project 

 from the sides of the midrib, makes it easier to follow the 

 entrance of the spermatozoid than is the case in most Ferns. 

 The spermatozoids collect about the mouth of the freshly- 

 opened archegonium, and soon one finds its way in. With the 

 ciliated end down, it revolves rapidly, not seeming to be much 

 impeded by the mucilage throwni out by the archegonium. 

 Suddenly, with a quick movement, quite unlike the slow worm- 

 like movement seen in most Ferns, it slips through the neck 

 into the central cavity, where its movement is resumed. After 

 about three or four minutes it disappears, and has presumably 

 penetrated the egg. Other spermatozoids may make their 

 way into the central cavity, but only one penetrates the ovum. 

 The lower neck cells now approach, but not enough to prevent 

 the entrance of other spermatozoids. Within a few hours the 

 inner walls of the neck cells begin to show the brown colour 

 that indicates that fertilisation has been accomplished. 



The egg quickly secretes a cellulose membrane, which 

 prevents the entrance of the other spermatozoids. The egg 

 nucleus moves towards the receptive spot at the time of 



