THE HIGHER CRYPTOGAMIA. 161 



the columella. The latter consists of a central group of 

 smaller cells with thinner walls, and a peripheral layer of 

 cells containing chlorophyll, which adjoins the mother-cells 

 of the spores. The cells of the outermost of the two layers, 

 which adjoin the primary mother-cells, are four times as 

 large as those of the inner layer. 



The cells of the layer of the columella adjoining the 

 primary mother-cells, as well as those of the future inner 

 wall of the capsule, are distinguished in a remarkable 

 manner from all other cells of the theca, by the great concen- 

 tration of the cell-contents, which are rich in dextrine. 

 The large cells of the centre of the columella contain small 

 amyloid masses of peculiar structure : minute firm granules, 

 which become intensely blue under the action of iodine, are 

 embedded in a gelatinous mass, which assumes a light blue 

 colour under the same action. 



The primary mother-cells, at this stage of their develop- 

 ment, contain a large central nucleus, which has usually 

 only one nucleolus, and somewhat transparent fluid con- 

 tents (PL XXI, fig. 5 ; PI. XXII, fig. 9). The remaining 

 contents of the cell, which consist of a thick fluid 

 mucilage rendered turbid by numerous granules, make it 

 somewhat difficult to distinguish the outline of the 

 nucleus. 



The greater number of the primary mother-cells divide, as 

 the fruit becomes developed, by means of a longitudinal or 

 transverse septum perpendicular to the outer surface of the 

 theca; more rarely by means of a longitudinal septum 

 parallel to that outer surface (PI. XXI, fig. 6). The dis- 

 appearance of the primary nucleus of the cell, and the pro- 

 duction of two new nuclei, precede the appearance of this 

 septum. The contents divide into two halves, each of which 

 surrounds one of the newly-formed nuclei (PL XXI, fig. 6,<$) ; 

 at the point of contact these two halves secrete the new 

 cell-wall, which consists of a very delicate layer of cellulose 

 (PL XXI, fig. 6, a)* 



Sometimes when the development of the fruit is very 

 active, the above division is repeated in the secondary 



* The two halves represented in the figure have contracted under the in- 

 fluence of water, to which, in Phascum, they are very susceptible. 



11 



