i;o REPRODUCTION 



In the brown Parmeliae, Rosendahl 1 found the same series of apothecial 

 tissues, but he interprets the course of development somewhat differently: 

 the basal dark layer or hypothecium he found to be of purely vegetative 

 origin ; above it extended the lighter-coloured subhymenium ; the ascogenous 

 hyphae were present only in the second layer of dark tissue immediately 

 under the hymenium. 



In most lichens the primordium of the apothecium arises towards the 

 lower side of the gonidial zone, the hyphae of which retain the meristematic 

 character. In Parmeliae, as was noted by Lindau 2 in P. tiliacea, and by 

 Baur 3 and Rosendahl 1 in other species, the carpogonial groups are formed 

 above the gonidial zone, either immediately below the cortex as in P. glabra- 

 tula, or in a swelling of the cortex itself as in P. aspidota, in which species 

 the external enlargement is visible by the time the trichogynes reach the 

 surface. In P. glabra, with a development entirely similar to that of P. as- 

 pidota, no trichogynes were seen at any stage. The position of the primordium 

 close under the cortex is also a feature of Ramalina fraxinea as described 

 by G. Wolff 4 . The trichogynes in that species are fairly numerous. 



A further peculiarity in Parmelia acetabulum attracted Baur's 3 attention. 

 Carpogonia with trichogynes are extremely numerous in that species as are 

 the spermogonia, the open pores of which are to be found everywhere between 

 the trichogynes, and yet fertilization can occur but rarely, as disintegrating 

 carpogonia are abundant and very few apothecia are formed. Baur makes 

 the suggestion that possibly cross-fertilization may be necessary, or that the 

 spermatia, in this instance, do not fertilize and that development must 

 therefore be apogamous, in which case the small number of fruits formed is 

 due to some unknown cause. Funfstiick 5 thought that degeneration of the 

 carpogonia had not gone so far, but that a few had acquired the power to 

 develop apogamously. In Parmelia saxatilis only a small percentage of 

 carpogonia attain to apothecia, although spermogonia are abundant and in 

 close proximity, but in that species, unlike P. acetabulum, a large number 

 reach the earlier stages of fruit formation ; the more vigorous apothecia seem 

 to inhibit the growth of those that lag behind. 



bb. PERTUSARIAE. In Pertusaria, the apothecial primordium is situated 

 immediately below the gonidial zone; the cells have a somewhat larger 

 lumen and thinner walls than those of the vegetative hyphae. In the asco- 

 gonium there are more cells than in Parmelia acetabulum \ the trichogynes 

 are short-lived, and several carpogonia probably enter into the formation of 

 each apothecium ; the paraphyses arise from the covering hyphae. So far the 

 course of development presents nothing unusual. The peculiar pertusarian 

 feature as described by Krabbe 8 , and after him by Baur 7 , does not appear 



1 Rosendahl 1907. a Lindau 1888. 3 Baur 1904. 4 Wolff 1905. 



8 Funfstiick 1902. * Krabbe 1882. 7 Baur 1901. 



