402 



THE FORMS OF TISSUES 



[CH. 



undivided quadrants, one of which has further slowly divided 



in the stage 6. The active quadrant 

 has grown quickly into a cylindrical 

 structure, which inevitably divides, in 

 the next place, into a series of trans- 

 verse partitions ; and accordingly, this 

 mode of development carries with it 

 the presence of a single "apical cell," 

 whose lower wall is a spherical surface 

 with its convexity downwards. Each 

 cell of the subdivided cylinder now ap- 

 pears as a more or less flattened disc, 

 whose mode of further sub-division 

 we may prognosticate according to 

 our former investigation, to which 

 subject we shall presently return. 

 (2) In the next place, still keeping to the case where only one 

 of the original quadrant-cells continues to grow and develop, let 

 us suppose that this growing cell falls to be divided when by 

 growth it has become just a little greater than a hemisphere; it 



Fig. 183. 

 Sphagnum. 



Development of 

 (After Campbell.) 



Fig. 184. 



will then divide, as in Fig. 184, 2, by an oblique partition, in the 

 usual way, whose precise position and incHnation to the base will 

 depend entirely on the configuration of the cell itself, save only, 

 of course, that we may have also to take into account the possibiUty 

 of the division being into two unequal halves. By our hypothesis. 



