IV 



THE JUNGERMANNIACE/E 



107 



Frullania the lower cell of the embryo, instead of remaining 

 undivided, or forming simply a row of cells, divides repeatedly, 

 and the cells grow out into papillae, so that it probably is 

 functional as an absorbent organ, like the foot of the Antho- 

 ceroteae. Radula ^ and Jimgerma7inia, while more regular in 

 the divisions than Porella, still arc less so than Frullania, and 

 in these more than the upper tier of cells take part in the 

 growth of the capsule. The degree to which the seta and foot 

 are developed varies. In Porella there is not a distinctly marked 

 foot, the lower part of the seta being simply somewhat enlarged, 

 but in others, like Jungeruiannia bicuspidata, there is a large 

 heart-shaped foot, very distinct from the seta. In Porella the 

 seta is short, projecting but little beyond the perianth ; but in 

 others it may reach a length of several centimetres. 



The development of the perianth is quite independent of 



Fig. 50. — Frullania dilatata (Nees). Development of the embrj-o, X 300 (after Leitgeb) ; x, .v, the 

 archesporial cells. The numbers indicate the primary transverse divisions. 



fertilisation, and not infrequently it contains, although fully 

 developed, only abortive archegonia. It is not always formed, 

 but when present, according to Leitgeb,- it is the product of the 

 older segments of the apical cell from which archegonia are 

 formed, and arises as a sort of wall about the whole group of 

 archegonia. In Porella, as well as most of the foliose Hepaticae, 

 the capsule opens by four equal valves, the lines of splitting 

 corresponding, according to Leitgeb, to the first quadrant walls 

 in the young embryo. 



The germination of the spores shows a great deal of varia- 

 tion, and has been studied in a large number of forms by 

 several observers. Recently a number of tropical species have 

 been investigated, especially by Spruce ^ and Goebel,"* and some 

 extremely interesting variations have been discovered. In these 



^ Hofmeister (i). - Leitgeb (i), vol. ii. p. 47. 



Spruce (2). 



Goebel (12) 



