642 THE FORMS OF TISSUES [en. 



seen it appear in cases where the entire system consists of eight 

 cells only. For example, we have it in a section of a young embryo 

 of a moss (Phascum), and again, in a section of an embryo of a 

 fern (Adiantum). In Fig, 290, shewing a section through a growing 

 frond of a sea-weed (Girardia), we have a case where the partitions 

 forming the eight octants have conformed to the usual type; but 

 instead of the usual division by periclines of the four quadrangular 

 spaces, these latter are dividing by means of oblique septa, apparently 

 owing to the fact that the cell is not dividing into two equal, but 

 into two unequal portions. In this last figure we have a peculiar 

 look of stiffness or formahty, such that it appears at first to bear 

 little resemblance to the rest. The explanation is of the simplest. 

 The mode of partitioning differs little (except to some slight extent 



Fig. 280. (A, B) Sections of younger and older embryos oi Phascum; 

 (C) do. of Adiantum. After Kienitz-Gerloff. 



in the way already mentioned) from the normal type; but in this 

 case the partition walls are so thick and become so soon com- 

 paratively solid and rigid, that the secondary curvatures due to their 

 successive mutual tractions are here imperceptible. 



A curious „and beautiful case, apparently aberrant but which 

 would doubtless be found conforming strictly to physical laws if 

 only we 'clearly understood the actual conditions, is indicated in 

 the development of the antheridium of a fern, as described by 

 Strasblirger. Here the antheridium develops from a single cell, 

 which (Fig. 291) has grown to something more than a hemisphere; 

 and the first partition, instead of stretching transversely across the 

 cell, as we should expect it to do if the cell were actually spherical, 

 has as it were sagged down to come in contact with the base, and 

 so to develop into an annular partition, running round the lower 



