530 MR. H. MABSHAXL WABD ON 



curvature follows very rapidly, and appears not always to start in 

 the same direction, though later the apex of the ovule is curved 

 directly downwards to the ventral face of the carpel. 



On comparing the figures with those of Butomus, it will be 

 noted that the cells are smaller and more numerous, and the 

 changes are more rapid in proportion. In Plate XXI. fig. 2 a 

 cell at the apex of the axial row already becomes distinguishable 

 by its sharp outline, bright nucleus, and granular contents ; it is 

 the embryo-sac mother cell in the sense already defined. 



In Plate XXI. fig. 4 (which is younger than fig. 3) this cell 

 has elongated and contains a very large nucleus ; the first divisions 

 to form the integument are seen at the convex part of the epi- 

 dermis. Only one integument is formed. The subepidermal 

 cells have also commenced to divide, first by walls parallel to the 

 epidermis, then by walls in a vertical plane ; and we get a similar 

 series of groups radiating from the axial row to those met with 

 in Butomus. The chief difference is in their smaller number. 

 They are pulled out, so to speak, in just the same manner, and 

 probably from the same cause. 



In Plate XXI. fig. 3 a, which is a magnified drawing of the 

 lowest ovule in the section sketched at fig. 3, we find the embryo- 

 sac mother cell has cut off a cell at its upper two thirds ; and 

 in Plate XXI. fig. 5 a second cell appears above by a repetition 

 of this process. The lower cell of the three grows a little, 

 while the two upper ones begin to appear ill-defined, lose their 

 nuclei, and finally (Plate XXI. figs. 6 and 7) their contents 

 become very refractive, and their walls weak and compressed by 

 the cells around. It would appear finally as if these contents 

 were absorbed by the surrounding cells (Plate XXI. fig. 8) ; for 

 they entirely disappear, with the exception of a thin bright band 

 seen at times as a kind of beak to the embryo-sac. 



In Plate XXI. fig. 8 two nuclei have formed in the sac, and 

 appear to be engaged in the first division. I have not followed 

 this further ; but in Ranunculus repens a normal egg-apparatus, 

 nucleus, and antipodes occur, just as described by Strasburger for 

 Myosurus, with which also may be compared this account. 



In the more mature ovule also the structure of the nucellus 

 presents features quite similar to that of Butomus ; and, as there, 

 any argument derived from the mode of division of the cells is 

 equally applicable to the radiating groups which start from the cells 

 sheathing the axial row, and to the axial row itself. And in all 



