580 



THE FORMS OF TISSUES 



[CH. 



be a minimum, three only must meet in a point; and therefore, 

 the four quadrantal walls must shift a Uttle, producing the usual 

 little median partition, or cross-furrow, instead of one common 

 central point of junction. This intermediate partition, however, 



Fig. 230. Development of Erythrotrichia. After Berthold. 



will be small, and to all intents and purposes we may deal with the 

 case as though we had now to do with four equal cells, each one 

 of them a perfect quadrant; so our piroblem is, to find the shortest 

 line which shall divide the quadrant of a circle into two halves of 



Fig. 231. 



equal area. A radial partition (Fig. 231, A), starting from the 

 apex of the quadrant, is at once excluded, for the reason just referred 

 to ; our choice must lie between two modes of division such as are 

 illustrated in Fig. 231, where the partition is either (as in B) con- 

 centric with the outer border of the cell, or else (as in C) cuts that 



