282 H0FME1STER, ON 



cells by septa parallel to the outer surface (PL XXXVI, 

 fig. 9). A previous division takes place by septa which 

 cross one another in different directions, and are perpen- 

 dicular to the outer surface, and by such division the cir- 

 cumference of the wall is increased, keeping pace with the 

 increase in volume of the group of mother-cells. In the 

 mean time the division by septa parallel to the outer surface 

 occurs once more, so that now the wall of the sporagium 

 consists of three layers of cells (PL XXXVI, fig. 10). 



The inner one of these layers and the middle one be- 

 come dissolved, and are displaced by the group of mother- 

 cells, the size of which increases continually. The inner layer 

 is dissolved at an early period, and the middle one shortly 

 before the time when the mother-cells are individualised 

 (PL XXXVI, fig. 13). The connexion between the mother- 

 cells is not broken up all at once. Small groups, consisting 

 normally of four cells, usually hang together for some time 

 (PL XXXVI, figs. 11, 12). This process corresponds ex- 

 actly with what takes place in the formation of the pollen 

 of phaenogams. 



Each of the spore-mother-cells when free exhibits a large 

 central nucleus, as is the case at all periods of their deve- 

 lopment, except immediately before the division of a gene- 

 ration of mother-cells. This nucleus, which usually has 

 only one moderate-sized spherical nucleolus, is a globular 

 empty cavity, having a vesicular appearance, and is filled 

 with fluid which is less highly refractive than the thickly 

 mucilaginous contents of the cell, which are rendered turbid 

 by numerous fine yellowish granules. In the further 

 progress of the development of the fruit the membrane 

 of this nucleus is slowly dissolved : its fluid contents do 

 not intermingle with that of the cell (PL XXXVI, fig. 12; 

 PL XXXVII, fig. 1). In its place two large flatly ellip- 

 soidal nuclei suddenly appear occupying almost half the 

 mother-cell. These latter nuclei at first exhibit no nu- 

 cleoli, but at a later period they contain several (PL 

 XXXVI, fig. 3). In the equator of the cell, between 

 the two nucleoli, a ring or plate of protoplasmic granules 

 is formed near the cell- wall (PL XXXVII, figs. 4, 5). 

 The outlines of the two flattened nuclei then become more 



