BRYOPHYTES. 



51 



which shows that the epidermis is not sharply diffe- 

 rentiated from the inner tissues. Adventitiously-formed 

 rhizoids are exceedingly common. Vochting found that 

 when, in Lunularia, all the rhizoids were cut off close 

 to their point of origin on the young thallus, new ones 

 grew out from the lower surface. 



Forest Heald induced rhizoid -formation, in Mnium 

 rosfratum and Funaria hygrometrica, from both sides 

 of detached leaves in both light and darkness ; he 

 found that nothing short of complete separation of 

 the leaf from the stem would induce rhizoids to 

 appear. Fig. 11 shows adventitious protonemata- 

 springing from a separated leaf of Funaria. In 

 Funaria portions of stem torn away with the leaves 

 also produced protonemata. He found that proto- 

 nemata or rhizoids w r ere only formed from special 

 cells of the leaf-base in Barbula, Brachythecium, and 

 Funaria ; and only from special cells of the ventral 

 leaf-surface in Atrichum and Polytrichum ; on the 

 other hand, from all leaf-cells in Mnium, Bryum, and 

 Phascum. In Bryum, Barbula, Brachythecium, and 

 Phascum protonemata only were formed in light, 

 and rhizoids only in the dark ; in Atrichum and 

 Polytrichum protonemata only were formed in both 

 light and darkness. 



Westerdijk caused protonema-formation from leaves, 

 stem, or rhizoids (fig. 12) of mosses by means of 

 mutilation. 



Correns also describes numerous cases of adven- 

 titious protonema-growth. 



Pringsheim found that protonemal threads grew 

 from the cells of the cortical region in cut pieces of 

 the stem of certain mosses. 



Goebel observed protonemata growing from the 

 inner side of the calyptra in the moss Gonomitrium 

 Julianum, and Limpricht found the same thing in 

 detached calyptraB of Phascum. 



Schimper states that in the moss Oncophonis glaucus 

 the perichsetial leaves form masses of " proembryonic 



