498 EXPLANATION OF THE PLATES. 



f. A cell composed of almost homogeneous mucilage, 

 with a lateral nucleus. Diam. of the cell = -315. 



g. A cell, in which a delicate membrane is distinctly 

 visible outside the finely granular contents. The nucleus 

 possesses five nucleoli ; its contents are less dense than 

 those of the cell. Diam. of the cell = '020 of a line. 



Fig. 9. Formation of the nucleus in the embryo-sac in 

 various plants. 



a. A nucleus with a lateral nucleolus of brighter (less 

 dense) substance. Diam. of the nucleus = '004 of a line. 



b. A nucleus with a nucleolus of denser substance. 

 Diam. of the nucleus = *005 of a line. 



c. A nucleus with a nucleolus, both consisting of ho- 

 mogeneous mucilage of the same density. 



d. The same nucleus altered by the injurious influence 

 of water. The mucilage of nucleus and nucleolus has 

 become more dense ; a vacant space (filled with water) 

 has formed around the latter. Diam. of the nucleus = 

 009 of a line. 



e. A nucleus with three nucleoli, both consisting of 

 equally dense, homogeneous mucilage. 



/. The same nucleus altered by the injurious influence 

 of water. A transparent space has formed around each 

 nucleolus. The contents of the nucleus and nucleoli 

 have contracted. Diam. of the nucleus = *010 of a line. 



g. An abnormally altered nucleus, like d and/. 



h. An abnormally altered nucleus, like d and/. 



i. The same nucleus a short time after. The mem- 

 brane expands out into a vesicle at one side in conse- 

 quence of the endosmose of water. 



k. The same nucleus later still ; the vesicle has become 

 still larger. 



/. An abnormally altered nucleus with two nucleoli, 

 the membranes of which have, in like manner, expanded 

 out into a vesicle on one side, as in i and k. 



m. An abnormally altered nucleus with one nucleolus, 

 the membrane of which has merely expanded into a 

 vesicle at one small point. 



