i 9 2o] HAUPT—FOSSOMBRONIA 328 



occur, and walls come in to separate the 4 members of the tetrad 



(fig. 43)- 



The material available for the investigation yielded no stage 

 beyond that shown by fig. 44. No spiral thickenings were visible 

 on the wall of the elaters, and the spores were in various stages 

 of separation from their tetrads. The seta at this stage is not 

 yet elongated. Evans (3) has made a careful study of the mature 

 spores and elaters of this species. He says: 



The elaters .... are remarkable not only on account of their small size 

 and delicate structure but also on account of their variability in form and 

 scanty development. Their most usual features, however, are found in the 

 local thickenings on their walls. Instead of forming 2 or more parallel spirals, 

 these usually consist of from 5 to 9 rings, some of which may be connected to 



form a single rudimentary spiral The elaters vary from 28 ^ to 50 ju. in 



length and from 6 p. to 18 fx in width. The bands of thickening are less deeply 

 pigmented than in most species of Fossombronia and are sometimes very pale 



indeed and difficult to demonstrate The brown spores in the type 



material are mostly between 36 //, and 40 //. in diameter The spherical 



face is covered over with a more or less regular reticulum formed by inter- 

 secting lamellae about 2 fx in height The meshes of the reticulum are 



mostly 8-10 /a wide and the spherical face usually measures 6 or 7 meshes 

 across. Sometimes the reticulum is irregular or incomplete. 



The mature capsule is globular or nearly so; its wall is in- 

 variably 2 cells thick and bears rudimentary annular and half-ring 

 fibers on the walls of the inner layer (fig. 46). There is no sterile 

 cap at the apex of the capsule. Dehiscence, according to Cavers 

 (2), is by means of 4 valves in some species of Fossombronia, but 

 in most of them the upper part of the capsule breaks into plates 

 which are cast off irregularly. 



Summary 



1. The vegetative body of F. cristula consists of a minute, 

 creeping, rather profusely branched thallus which bears genuine 

 leaves in 2 dorsal rows. 



2. The apical cell is dolabrate. Branching is strictly apical. 



3. The plants are monoecious, the sex organs occurring in the 

 axes of the leaves. Antheridia and archegonia may occur in the 

 same leaf axis, and there is no time relation in the order of their 



