8o COMMON LI VER IVOR T. 



kinds. One is a very common method, by which the 

 stems die off at the older end as fast as they grow at 

 the other. In this way the branches are eventually 

 separated from each other and become independent 

 plants. The other is a peculiar method by which cer- 

 tain hairs at the bottom of cupules grow into flat green 

 plates, the gemmae, which as they become mature are 

 pushed out of the cupules by the aid of the secretion 

 from the glandular hairs. 14 The gemmae have their 

 direction of growth changed at a very early stage by 

 the formation of a right and left growing point, so that 

 the young plantlet is bifurcated at its outset. - When 

 a gemma has fallen upon the ground, the side which 

 happens to be uppermost is developed as the upper 

 surface of the thallus, and the other becomes the lower 

 surface. 15 The root-hairs grow from the cells devoid 

 of chlorophyll. 



The sexual reproduction is among the most highly 

 developed of that shown by the liverworts. The organs 

 are upon branches whose modification is so interesting 

 that it will be necessary to examine it somewhat care- 

 fully. The plants are dioecious, bearing the reproductive 

 organs on separate individuals. In each case the repro- 

 ductive branch consists essentially of an attenuated por- 

 tion, the pedicel, terminated by an expanded portion, the 

 head, on which last the sexual organs are borne. The 

 pedicel is not a single branch, but two which are the 

 result of dichotomy at the point where it leaves the 



14 Fide Strasburger, Das botanische Practicum, p. 436. 



15 Engelmann, Ueber die Einwirkung des Lichtes auf den March- 

 antienthallus in Arb. d. bot. Inst. in Wurzburg, Bd< ii, p. 665 ; Mirbel, 

 Mem. Acad. Sci.de Fr., xiii (1835), p. 355. 



