ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 349 



found the ascogonial initial cells, such as have been described by Stahl 

 and others, in the very early stages of growth, and his aim has been to 

 determine their significance. He found that the young apothecium in 

 Solorina saccata took rise in the lower part of the algal layer, and that 

 there was no trace of fertilisation, nor formation of trichogynes. The 

 ascogonial cells were not multinucleate ; they gave rise by branching to 

 a complex growth of hyphaj from which the asci were developed. The 

 paraphyses had a different origin and were formed before the asci. 

 There are no spermogonia developed in Solorina. Very similar results 

 were found in Acarospora glaucocarpa. No trichogynes are formed, and 

 no spermogonia are present. The apothecium arises more in the middle 

 of the algal layer. In Verrucaria calciseda it took origin underneath 

 this layer ; here also there were ascogonia formed, but no trichogynes, 

 though spermogonia and spermatia were present. The development of 

 the fruit was entirely non-sexual. In Imbrkaria physodes the asco- 

 gonium was composed of three initial cells produced by branching from 

 the ordinary hypha?, on the upper side of the green layer. No previous 

 copulation of the initial cells could be detected and no trichogynes were 

 formed, though spermogonia are present. The many black points so 

 characteristic of this Lichen were found to be apothecia degenerated at 

 an early stage. Metzger examined Peltigera canina, and found here 

 also vegetative or non-sexual development only ; spermogonia are rarely 

 developed. He gives an account of the best methods of treating the 

 thallus to ensure the detection of the early stages of the apothecium. 

 He found benzine derivatives especially useful, as they possess the pro- 

 perty of reacting with oxidising agents, to form coloured substances, 

 and thus marking off the tissue surrounding the ascogonium, which 

 contained some oxidising agent that was absent in the ascogonium 

 itself. 



Erwin Baur * has also published the results of his researches on this 

 subject. He begins by reviewing the work that has been already done, 

 and emphasises its importance from a systematic point of view. He 

 gives details as to his methods of examination, and then gives the 

 results of his work on the different forms. In Parmelia Acetabulum he 

 finds that an immense number of carpogonia and spermogonia are 

 formed similar to those of Collema, but very few apothecia are matured ; 

 cross fertilisation may be necessary to ensure further growth or the 

 carpogonium may develop apogamously. He thinks that probably more 

 than one series of initial ascogonial cells is included in each apothecium. 

 He found the same type of carpogonium in Anaptyehia, Endocarpon, 

 Gyrophora, Lecanora and Cladonia, all of which he considers to be 

 sexual in their mode of development. In Anaptyehia and Endocarpon 

 especially, he observed spermatia at the apex of the trichogyne, though 

 the further stages of fertilisation have not been followed. In Cladonia 

 the carpogonium arises at the base of the fruit, the podetium is there- 

 fore not a modified apothecium, as Krabbe supposed it was. Several 

 other genera, Solorina, Peltiyera, Peltidea and Nephromium are probably 

 non-sexual ; the carpogonia have become non-sexual, no trichogynes are 

 formed, and the spermogonia are absent or poorly developed. 



* Bot. Zeit,,lxii. (1904) pp. 21-44 (2 pis.). 

 June 15th, 1904 2 b 



