THE EMBRYO-SAC IN ANGIOSPEBMS. 545 



Fig. 5. Transverse section of nucellus about the same stage. 



6. Similar preparation to fig. 4 ; but two cells appear to be absorbing the 



rest. 

 7 & 8. Similar preparation. Fig. 7 is drawn at a higher focus ; and its 



nucleus lay above that of fig. 8. Probably two cells still exist. 

 9 & 10. Similar preparation. Fig. 9 is drawn at higher focus than fig. 10: 

 there are two cells with very weak walls, absorbing the rest of the 



nucellus. 



11. The cell has absorbed the whole of the nucellus, and is growing out to 



occupy the space between the integument folds. Remains of nucellus 

 epidermis-cells surround its proximal half. 



12. One cell (possibly two) occupies the whole space, and is now closely 



surrounded by the integuments ; it contains at least two nuclei. 



Plate XXIV. 



Vyrethrum balsaminatum (continued). 



Figs. 1 & 2. Ovule about time of fertilization. The integument closely invests 



the embryo-sac (which appears to have resulted directly from the one 

 dominant cell traced above) ; and the cells of its inner layer become 

 thick -walled and radiate away from the sac ; immediately around the 

 sac, however, they form an epidermis-like layer. 



Inside the sac are masses of protoplasm connected by bridles : that 

 at the micropyle end contains a normal egg-apparatus ; that in the 

 middle contains four nuclei, apparently produced by division. (Fig. 2 

 under Hartnaek 4.) 

 Fig. 3. Similar preparation of slightly younger ovule : constituents of egg- 

 apparatus are formed, but the curved lines are not explained. There 

 is a nucleus about the centre, and one or two at antipodal end. 



Anthemis tinctoria. 



4. Vertical section of very young ovule, one cell at apex already distin- 



guished by its large nucleus. 



5. Similar preparation of slightly older ovule. At a, peculiar banded 



nucleus (shown more magnified at fig. 6), such as occurs here and 

 there in rapidly growing tissues. 



6. Banded nucleus enlarged, as above mentioned. 



7. Slightly older ovule ; the one cell at apex is elongating, and the integu- 



ment commences to arise by subepidermal division. 



8. Slightly older ovule. The one cell at apex now occupies the main 



part of nucellus, and the integument is spreading over the anatropous 



ovule. 



9. The integument closes in as before, and leaves a space between itself 



and the apex of nucellus : only one cell fills up the interior of the 



latter. 



