252 Mr. W. H. Lang. Preliminary Statement on the 



neck closed and branched. The central cell of the abnormal anthe- 

 ridia is arrested at a more or less early stage of development, while 

 the cells of the wall and the base take on active growth. 



The sporangia are either isolated or associated together in groups, 

 which bear a striking resemblance to sori. They are borne upon the 

 process or close behind it upon the true middle lobe, and are rarely 

 found upon prothalli which have not produced a cylindrical process. 

 When this is the case, they are always isolated and situated on the 

 edge of a thin continuation of the prothallus arising from the apical 

 depression. 



Single sporangia occur frequently on the edge of the prothallus, 

 which, as described above, crosses the base of the process. In a 

 number of examples a single sporangium occupied a median posi- 

 tion, and, from earlier stages observed, it is probable that it is to be 

 traced back to the original growing point of the prothallus. In other 

 cases several sporangia were formed in this region. Isolated spo- 

 rangia are also found on the process, but more frequently groups are 

 met with. They occupy the upper or lateral faces of the process, 

 and whenever sporangia in early stages of development are found, 

 they are situated on its apex. It is probable that the groups of 

 older sporangia had become displaced from this position by the fur- 

 ther growth of the process. The groups were at a considerable dis- 

 tance from each other. 



The relative positions of sporangia and sexual organs is a point 

 t>f some interest, and was readily determined. Archegonia were 

 present close to the sporangia, and at the same level on the 

 process. When the process, after producing sporangia, had con- 

 tinued its growth, archegonia and antheridia were present on the 

 portion beyond the sporangia, as well as on the older part, and, in 

 cases in which more than one group of sporangia had developed, the 

 intervening region bore sexual organs. Rhizoids are also produced 

 abundantly from the shaded side of the process, and, so far as exter- 

 nal appearance is concerned, there is no reason to doubt the pro- 

 thallial nature of the region on which the sporangia are situated. 

 The tissue underlying the .sporangia, however, presents peculiarities 

 in structure which may modify this conclusion to some extent. 

 Beneath the single sporangia developed on the edge of the prothallus 

 a few tracheides, which agree in every respect with those present in 

 apogamous prothalli, were always to be found. Similar elements 

 were always present in the tissue beneath the groups situated on the 

 process. It is possible that here, as in the case of the sporangia 

 upon the prothallus edge, the first tracheides are developed before 

 the young sporangium can be recognised. All that can be stated 

 with certainty is that they are already present beneath very young 

 sporaugia. The tracheides may become connected together into a 





