472 



Mr. J. B. Farmer. On the 



[May 12, 



The antheridia are distributed both on the upper and lower surfaces 

 of the prothallium, and apparently without any approach to regu- 

 larity, though they are somewhat more frequent on the lower surface. 

 T may observe, however, that an antheridium may often occur on the 

 upper surface immediately above an archegonium which has been 

 fertilised. 



The archegonia occur exclusively on the lower surface. Their 

 development has been described by Jonkman, who also noticed the 

 division of the neck canal cell, by a transverse wall, into two cells. 

 The division is not, however, invariable, and in one preparation in 

 which the protoplasm had shrunk slightly from the wall, I observed 

 that the cell plate had not extended so as to completely partition the 

 neck passage into two cells. 



The neck canal, and ventral canal, cells become converted into 

 mucilage, which bursts open the archegonium, and thus admits of the 

 passage of the antherozoid to the oosphere. 



The oospore, after fertilisation, speedily forms an ovoid cellular 

 body, and although I was not so fortunate, owing to scarcity of 

 material, as to see the formation of the earliest cell walls, their suc- 

 cession could be determined with tolerable certainty in the youngest 

 embryo that I met with, consisting as it did of about ten cells. 



The basal wall is formed, as in Isoetes, at right angles to the axis 

 of the archegonium. The next one in order of occurrence I believe 

 to be the median wall, which can easily be distinguished, even in 

 advanced embryos, as a well-defined vertical line. 



The transverse wall is much more indefinite, and early loses its 

 individuality owing to the unequal growth of the various parts of the 

 young embryo. The further cell- division is irregular, and to a far 

 greater extent tban is the case with the leptosporangiate Ferns as 

 described by Hofmeister and Leitgeb. I was unable to determine 

 the constant occurrence of segment walls, though indications of them 

 could occasionally be seen in a few preparations. 



The anterior epibasal octants together give rise to the cotyledon ; 

 the stem-apex is formed, not as in the leptosporangiate Ferns, from 

 one octant only, but from both of the posterior epibasal octants, 

 though one of them contributes the greater portion. The truth of 

 this statement is seen , on examining vertical sections through the 

 embryo cut at right angles to tbe median wall, when a few cells on 

 each side are seen to be clearly marked out by their dense proto- 

 plasmic contents and large nuclei, as meristem cells. There is no 

 single apical cell in Art giopteris from which all the later stem tissue is 

 derived, and this fact is, without doubt, to be connected with the 

 character of the apical meristem just described. The root is formed 

 from one of the octants beneath the cotyledon, i.e., from an anterior 

 hypobasal one, and is at first indicated by a triangular apical cell, 



