542 MR. H. MARSHALL WABD ON 



Fig. 8. Transverse section of same stage across the nucellus and inner integu- 

 ment only ; the regular arrangement of the radial walls is especially 



evident. 

 9. Longitudinal section through older ovule, seen from before. Disre- 

 garding the axial row and its divisions, the enlarging nucellus-cells 

 are multiplying by further tangential a3 well as radial divisions : 

 the cells tend to bo arranged in rows radiating towards the periphery. 

 10. Similar section at slightly older stage, treated with warm potash. The 



contents of cells of the axial row &c. are dissolved away ; the radiating 

 groups of subepidermal cells tend towards a common centre below. 



Plate XVIII. 



Butomus timbellaius (continued) 



Fig. 1. Longitudinal section through nearly completed ovule : the loose and 



diffluent cells in upper part of the nucellus are becoming undistinguish- 

 able from the embryo-sac ; in lower part of nucellus they are arranged 

 in radiating rows towards the periphery. 

 Transverse section across lower third of similar ovide: ex. = outer in- 

 tegument; in.= inner ditto; w = nucellus. 



Long 



> 



treated with potash and glycerine ; the radiating groups of cells abut 

 upon the cells around the axial row, and converge towards a common 

 centre. They are more numerous than in fig. 10, PI. XVII. ; but, as 

 there, a typical group consists of a peripheral or terminal set of four or 

 eight, and a proximal undivided cell or cells abutting on the central 

 series : this is most clear where the group is in longitudinal median 

 section. 



4. Longitudinal section through ovule at stage slightly older than fig. 7, 



PI. XVII. The embryo-sac mother cell has divided once. 



5. Longitudinal section through older ovule : the large cell has again di- 



vided ; and the foremost of the two "cap-cells " thus cut off now pos- 

 sesses a vertical division- wall. 



6. Similar section of older ovule, from before. There appears to be an ab- 



normal number of divisions above. 



7. Similar preparation with normal divisions of embryo-sac mother cell : 



the second division-wall yery diffluent. 



8. The two cap-cells arc separated by oblique walls (abnormal ?). 



Plate XIX. 



Butomus umbellatus (continued). 



Pig. 1. The lower larger cell (of those into which the embryo-sac mother cell 



has divided, and which will become the embryo-sac) is dividing: two 

 nuclei pass to opposite ends ; and a vacuole-like space appears 

 between. This " vacuole " may be a very diffluent cell-wall. 

 2. Similar preparation of older ovule. There are two nuclei in the em- 

 bryo-sac; and remains of the " cap-cells" form a dark mass at it* 

 apex. 



