166 IIOFMKISTKll, ON 



If the primary mother-cells are unusually long or wide, 

 they divide, according to the ordinary method of cell-multi- 

 plication, before the formation of the spore-motlier-cells. 

 Two of such primary mother-cells then adjoin one of the 

 cells of the neighbouring cellular layers (PI. XXII, fig. 12). 

 In rare instances, four spore-mother-cells are found in one 

 primary mother-cell (PI. XXII, fig. 12 J ). 



The walls of the primary mother-cells, which at an early 

 period are very sensitive to the action of water, become 

 more so after the formation of the spore -mother- cells. If 

 a longitudinal section of a fruit in this stage of development 

 be placed in water upon a slide, the walls of the primary 

 mother-cells immediately burst, and the spore-mother-cells 

 are dispersed over the field of view. It is necessary to 

 examine the preparations in some saline solution. A solu- 

 tion of carbonate of ammonia is the most useful. 



In the natural course of things, the dissolution of the 

 walls of the primary mother-cells follows soon after the 

 formation of the spore-mother-cells. The spherical spore- 

 mother- cells then lie free between the columella and the 

 inner wall of the theca. Numerous mucilaginous granules 

 surround the central nucleus, the substance of which is as 

 clear as water (PI. XXII, fig. 13). 



During the further development of the fruit, the nucleus 

 of the spore-mother-cell approaches the cell-wall, and usu- 

 ally assumes a lenticular shape. The granules of the fluid 

 contents of the cell accumulate at its middle point, so as to 

 form a spherical group (PL XXII, f. 14), in w T hich the 

 nucleus is sometimes partially embedded. This accumula- 

 tion of granules divides afterwards into two halves (PI. 

 XXII, fig. 15); a spherical nucleus may often be seen in 

 each of these granular masses (PL XXII, fig. 16). Each of 

 the elongated groups of mucilage and granules divides anew 

 into two parts ; and then four spherical accumulations of 

 coarsely granular protoplasm are found in the mother- 

 cell. They are usually arranged at the four corners of 

 a tetrahedron (PL XXII, figs. 17, 18), and very seldom 

 lie in the same plane (PL XXII, fig. 19). Each of them 

 contains a nucleus. The outline of the primary nucleus 

 of the mother-cell becomes less and less distinct during 



