162 REPRODUCTION 



Baur confirmed Stahl's observations on the various developmental 

 changes. In several instances he found a spermatium fused with the tricho- 

 gyne, though he could not see continuity between the lumina of the fusing 

 cells. After copulation with the spermatium the trichogyne nucleus, which 

 occupied the lower third of the terminal cell, had disappeared, and the 

 plasma contents had acquired a deeper tint; the other trichogyne cells, 

 which had also lost their nuclei, were partly collapsed owing to the pressure 

 of the surrounding tissue, and openings were plainly visible through some 

 of the swollen septa, especially of the lower cells. In addition the ascogonial 

 cells, all of which were uninucleate, had increased in number by intercalary 

 division. Plasma connections were opened from cell to cell, but only in the 

 primary septa, the later formed cell-membranes being continuous. Asco- 

 genous hyphae had branched out from the ascogonium as a series of 

 uninucleate cell rows from which the asci finally arose. 



Baur's interpretation was that the first cell of the ascogonium reached 

 by the male nucleus after its passage down through the cells of the trichogyne 

 represented the egg-cell, and that, after fusion, the resultant nucleus divided, 

 and a daughter nucleus passed on to the other auxiliary-cells. No male 

 nucleus nor fusion of nuclei was, however, observed by him, and his deduc- 

 tions rest on conjecture. 



Krabbe 1 and after him Maule 2 found in Collcma pulposum reproductive 

 organs similar to those described by Stahl, but in a recent paper on an 

 American form of that species a peculiar condition has been described 

 by Freda Bachmann 3 . She 4 found that the spermatia originated, not in 

 spermogonia, but as groups of cells budded off from vegetative hyphae 

 within the tissue of the lichen and occupying the same position as spermo- 

 gonia, i.e. the region close below the upper surface. The trichogynes, therefore, 

 never emerged into the open, but travelled towards these internal spermatia, 

 and fusion with them was effected. The changes that afterwards took place 

 in the carpogonial cells were similar to those that had been recognized by 

 Stahl and Baur as consequent on fertilization. 



Additional cytological details have been published in a subsequent 

 paper 5 : after fusion with the spermatium the terminal cell of the trichogyne 

 collapsed, its nucleus became disintegrated and the cross septa of the lower 

 trichogyne cells became perforated, these perforations being closed again at 

 a later stage by a gelatinous plug. The nuclear history is more doubtful : 

 the disappearance of the nuclei from the spermatium and from the terminal 

 cell of the trichogyne was noted; two nuclei were seen to be present in the 

 penultimate cell, and these the author interpreted as division products of the 



1 Krabbe 1883. 2 Maule 1891. 3 F. Bachmann 1912. 



4 This species of Colletna has been described as Collemodes Bachmannianum by Bruce Fink 1918. 



8 F. Bachmann 1913. 



