320 BOTANICAL GAZETTE [april 



germination of the spores; he notes that 



makes 



ment regarding the development 



monoecious 



The most complete study of Fossombronia since Leitgeb is 

 that by Humphrey (6), who investigated F. longiseta, a species 

 occurring in California, The thallus reaches a length of 30 mm. 

 and develops genuine leaves like the other species of the genus. 

 The plants revive well after undergoing desiccation, and tuber-like 

 thickenings are formed on the stem in which fungi live. The 



or by exception dioecious. Humphrey's 

 account of the development of the antheridium is most interesting, 

 in that it departs widely from the usual Jungermanniales type. 



The initial cell of the antheridium is somewhat larger than the neighbor- 

 ing vegetative cells, and is readily distinguished from them by its deeper 



staining qualities Just previous to the first division the initial cell 



becomes considerably elongated, extending a third or more of its total length 

 above the surrounding cells. The first division results from the formation of 

 a horizontal wall which cuts off the stalk from the antheridium itself. Unlike 

 what occurs in the majority of the Jungermanniaceae, the next division, 

 instead of being vertical, is horizontal, thus dividing the antheridium mother 

 cell into two superimposed cells; whereas in Sphaerocarpus and Geothallus 

 another horizontal wall is formed, thus producing another cell, the two upper- 

 most dividing vertically to form the antheridium, while the basal cell, by a 

 series of transverse walls, forms the foot. 



In Fossombronia the development thus far agrees exactly with that in 

 Sphaerocarpus and Geothallus, except that in Fossombronia only one horizontal 

 division occurs in the antheridium mother cell, the stalk arising from the 

 basal cell formed by the first horizontal division. This basal cell later divides 

 horizontally, the uppermost segment becoming active in the formation of the 

 stalk, while the lower ordinarily does not divide again. Following the 

 horizontal division of the antheridium mother cell are two vertical divisions 

 forming planes at right angles to each other and dividing the antheridium 

 into octants. The next division results in periclinal walls for each of these 

 octants, and there thus arise eight central cells and eight periclinal ones 



Judging from the development of the antheridium, Fossombronia is more 

 closely related to Sphaerocarpus and Geothallus than to the higher forms of 

 the Jungermanniaceae Thus it seems that Fossombronia longiseta forms a 



* 



connecting link between such forms as Sphaerocarpus and Aneura. 



The development of the archegonium presents no striking 



from 



are formed 



