2 28 Alexander W. Evans, 



y. CupuLES 



The characteristic gemmae of Marchantia have been repeatedly 

 described. They consist of flat discoid structures, each bearing 

 two opposite marginal growing points in shallow indentations. 

 They are attached to the thallus by a short stalk, which joins the 

 margin of the gemma midway between the growing points, the 

 gemma in consequence being vertical in position. The gemmae 

 occur in clusters on the upper surface of the thallus and are 

 surrounded by a circular membranous outgrowth, forming a cup 

 or cupule. Although the gemmae are very imiform throughout 

 the genus, the cupules yield a few differences w^iich sometimes 

 assist in the determination of species. Two principal types occur : 

 in the one, the margin of the cupule is simply dentate to ciliate, 

 the teeth being sometimes scattered and sometimes close together ; 

 in the other type the margin bears a series of triangular pointed 

 lobes, the edges of which are dentate to ciliate. As an example 

 of the first type M. domingensis (Fig. 12, K) may be cited, while 

 M. polymorpha (Fig. 2, N) shows the second type clearly. 



