408 THE FORMS OF TISSUES [ch. 



surface) consists of eight cells only. For example, in Fig. 191, 



Fig. 191. (A, B,) Sections of younger and older embryos of Phascum; 

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



we have it again, in a section of a young embryo of a moss (Phas- 

 cum), and in a section of an embryo of a fern (Adiantum). In 

 Fig. 192 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 formality, 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 in the way already mentioned) from the normal type; 

 but in this case the partition walls are so thick and become 

 so quickly comparatively 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 



Fig. 192. Section through frond 

 of Girardia sphacehria. (After 

 Goebel.) 



