42 HUMPHREY 



tubes of more than usual length while some showed the forma- 

 tion of cross-walls very early. The young plants in the nutri- 

 ent solution have grown rapidly, producing in some instances 

 as advanced a development as is seen in Fig. 21, within eigh- 

 teen days. A very few young plants in which there was only 

 a slight germ-tube development had already begun to assume 

 the dorsi-ventral form common to this genus. Desiccated 

 plants of F'imbriaria, Riccia and Fossomb^-onia when placed 

 in Knop's solution revived quickly producing within a few 

 days a greatly increased number of rhizoids and in the case of 

 jFossojubronm, many more than the usual number of antheridia, 

 closely covering the dorsal surface of the young growing shoot. 

 From these and other results it seems highly probable that 

 Knop's nutrient solution exerts a stimulative influence upon the 

 development of the thallus, rhizoids, and reproductive organs 

 as well as the germination of the spores. Further investigation, 

 however, with solutions of varying strength and composition is 

 needed in order definitely to determine the nature and chemical 

 composition of the salt or combination of salts that act as a 

 stimulus to growth. 



According to Goebel,^ germination in the Marchantiese when 

 compared with other thallose liverworts presents certain char- 

 acteristic differences. He separates the product of germina- 

 tion of a spore of Preissia for example, into three structures, 

 /. (?., the germ-tube, the '* pro-embryo " and the young plant. 

 He finds that the "pro-embryo" is positively heliotropic and 

 develops at its end a flattened cell mass which he terms the 

 germ disk. This forms at right angles to the direction of the 

 light-rays and the young plant arises from one quadrant of the 

 germ disk as shown in his Fig. 95. 



On the same page he states that a similar germination is 

 common in the Riccieae contrary to the description and figures 

 of Campbell^ who studied the ^<txvs\\\\'AX\onoi Riccia tricho car fa 

 and a number of other forms. He refers to Campbell's Fig. 9, 

 p. 38, as failing to bear out his statement that the axis of growth 

 in the young plant is continuous with that of the germ-tube. 



' Loc cit., p. III. 



^Loc. cit., isted., p. 39; 2ded., p. 38. 



