404 



THE FORMS OF TISSUES 



[CH. 



includes all cases in which the act of cell-division does not lag 

 far behind that elongation which is determined by the specific rate 

 of growth. And it is also obvious that, under a common type. 



Fig. 186. Development of antheridium of Riccia. (After Campbell.) 



there must here be included a variety of cases which will, at first 

 sight, present a very different appearance one from another. 

 For instance, in Fig. 187 which represents a growing shoot of 

 Selaginella, and somewhat less diagrammatically in the young 



Fig. 187. Section of growing shoot 

 of Selaginella, diagrammatic. 



Fig. 188. Embryo of Jungermannia. 

 (After Kienitz-Gerloff.) 



embryo of Jungermannia (Fig. 188), we have the appearance of 

 an almost straight vertical partition running up in the axis of the 

 system, and the primary cell-walls are set almost at right angles 

 to it, — almost transversely, that is to say to the outer walls and 

 to the long axis of the structure. We soon recognise, however. 



