EXPLANATION OF THE PLATES. 497 



the membrane. In a and b the nucleus lies outside the 

 contents. In c the nucleus has been dissolved. 



Fig. 7. Scilla cernua Red. 



Formation of the nucleus in the embryo- sac. 



a. A little globular drop of homogeneous, colourless 

 mucilage, with a definite outline. Diam. =='002 of a 

 line. 



b. A similar one, with thinner mucilage, 



c. A globule of mucilage like a. Diam. *0025 of a 

 line. 



d. e. A larger globule of mucilage (nucleus) with an 

 included ring (nucleolus). Nucleus and nucleolus have 

 a similar density. Diam. of the former ='0045 of a line. 



/. A nucleus with an included nucleolus of equal 

 density. Diam. of the former ='008 of a line. 



g. A nucleus with two included nucleoli of equal 

 density. Diam. of the former =*009 of a line. 



Fig. 8. Tigridia PavoniaJuss. 



Cell-formation in the embryo-sac. 



a. A globular drop of homogeneous, colourless muci- 

 lage, with a definite outline (nucleus). Diam. = *001 of 

 a line. 



b. A nucleus with scarcely granular mucilaginous con- 

 tents. Diam. ='003 of a line. 



c. A nucleus in which some larger granules (nucleoli) 

 are visible. Diam. =*005 of a line. 



d. A nucleus with four denser nucleoli, on which has 

 been deposited a layer of homogeneous mucilage (cell) . 

 The mucilage of the cell is more dense than the contents 

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



e. A cell consisting of homogeneous mucilage, with a 

 free (central) nucleus. The contents of the latter are 

 less dense than the mucilage of the cell ; it includes four 

 denser nucleoli. Diam. of the cell = -010 of a line. 



32 



