464 INTEODUCTION TO CKYPTOGAMIC BOTANY. 



three strata of cells are reqmsite to form the teeth (Fio-. 

 100, a). 



511. It has been attempted to be shown that these teeth, 

 like petals, are modifications of leaves ; but there is no reason 

 to believe that this is the ease. They have never been seen 

 transformed into leaves, nor does their origin agree in the least 

 with that of leaves. The cases in which it has been reported 



Fig. 98. 



a. Barhula fallax, horizontal section of two cells, on the contiguous 

 walls of which two teeth are formed. 



b. Orthotricimm aJRne, ditto of the three cells from which the outer 

 row of teeth and the alternating cilia are formed. Both after Lantzius 

 Beninga. 



c. Archegonium and young sporangium of Phascum cus^pidatum, after 

 Hofmeister. 



d. Spermatozoids of Funaria hygrometrlca, after Thuret. 



that the columella has extended beyond the sporangium clothed 

 with leaves have rested on imperfect observations. The teeth, 

 indeed, are not organs developed on the walls, but mere modi- 

 fications of particular strata of cells, which enter into the com- 

 position of a body which was at first solid. The cavity of the 

 sporangium is not, in fact, comparable with the hollow recep- 

 tacle of Rosacece, which it ought to be if the peristome con- 

 sisted of leaves. The mode of development of the different 



