30 



THE OPHIOGLOSSALES 



mann was able to detect it in O. pendulum and 0. vulgatum. It is probable that 

 its apparent absence in most of the archegonia is due to the fact that it is formed very 

 late and is extremely inconspicuous. The same apparent absence of a ventral canal 

 cell in the Cycads and some Conifers has been shown, on more critical study of the 

 material, to be due to the small size of the ventral nucleus and to its very evanescent 

 character. In nearly all of the archegonia examined, just before they opened there 

 was present a vesicular body above the egg, which was probably the ventral canal 

 cell much distended with fluid preparatory to the opening of the archegonium. A 

 small nucleus, or what looked like one, could sometimes be seen, but it must be said 

 that its nuclear nature was not above suspicion (plate 2, fig. 33). 



Just before the archegonium is ready to open, the egg cell, which up to this 

 time is compressed above by the basal wall of the neck canal cell, becomes distended 

 and pushes up the base of the canal cell, which thus becomes concave below. It is 

 probably about this time that the ventral canal cell is cut off. Unfortunately, no 

 cases were found showing mitosis in the central cell, but there seems no good reason 

 to doubt that a ventral canal cell is, usually at least, cut off". 



Fig. 17. — Development of the archegonium in Botrychium virginianum. 

 A-D. Longitudinal sections. X320. 



E. Ripe archegonium, showing ventral canal cell D. X165. (After Jeffrey.) 



F. Recently fertilized archegonium, showing spermatozoids within venter. X3JO. 



The neck canal cell does not show the complete disorganization which is com- 

 mon, but retains its form up to the time that the archegonium opens. With the 

 opening of the neck there is some elongation of the outer neck cells, but there is 

 decidedly less projection above the surface of the prothallium in O. pendulum than 

 is the case in O. vulgatum. The nucleus of the egg cell is large, but it does not always 

 stain readily, except the nucleoli, and it may be that the same resistance to stains 

 is the reason why its sister nucleus in the ventral canal cell is so difficult to see. 



THE ARCHEGONIUM OF BOTRYCHIUM. 



The archegonia in Botrychium are found usually upon the flanks of the median 

 ridge, upon whose summit are borne the antheridia. In their early stages they 

 closely resemble those of Ophioglossum (fig. 17). As in the latter, there is some 

 variation in the form of the mother cell, which may be quite deep and narrow, or 

 relatively broad and shallow. The subsequent divisions in the central cell and in 



