636 SUMMARY OF CURRENT RESEARCHES RELATING TO 



trary, that when light roached the thallus from below only, a larger 

 number of hairs were produced on the upper than on the under side. 

 The results were precisely similar for both Marchantia and Lunuliiria. 



With regard to the dorsiventral thallus which proceeds from a 

 gemma, Zimmermann confirms Pfeifer's statement that the organic 

 upper surface which produces stomata is always the one directly 

 exposed to light. 



The results obtained from the thallus of the Marchantiese corre- 

 spond in all respects to those recorded by Leitgeb * in the case of 

 the prothallia of ferns ; only in the latter there is not nearly so 

 completely difierentiated a tissue-system. There appears to be also 

 a diifercncc between them in this respect, that when the dorsivcn- 

 trality of the thallus of the He2iatica3 is once established, it cannot 

 be reversed ; while the contrary is the case with the prothallia of 

 ferns, which may even produce archegonia on both sides. 



Fungi. 



Hymenomycete with the Hymenium on the Upper Side. — The 

 note on this subject at p. 488 was wrongly headed as " on the under 

 side," instead of " upper." 



Superior Hymenium in the Hymenomycetes.t — In accordance 

 with the observations of de Seyues, of a superior hymenium in species 

 of Agaricus, P. Magnus has observed a similar phenomenon in 

 Hydnum repandum near Fontainebleau. 



The upper surface of the pileus bears a number of vermiform 

 excrescences, on the free surface of which is seated the spiny hyme- 

 nium, which grows partly vertically upwards, partly downwards from 

 the elevated margin of the excrescences. The ordinary positive 

 geotropism may thus become transformed into the negative, as is 

 ordinarily the case with the Clavariefe, whose hymenium grows 

 vertically upwards. In both cases the effect is the same. In all the 

 Hymenomycetes with isolated hymenium, as the Clavariese, Hydnaceje, 

 Polyporeae, and Agaricinese, the growth of the hymenium proceeds 

 vertically either upwards or downwards, the sporiferous basidia being 

 in consequence in both cases horizontal. 



Structure of the Annulus in Hymenomycetes4 — In some 

 species of Agaricus the annulus proceeds from the base of the stipes, 

 as in A. melleus, and there is no free volva. In these cases, according 

 to M. Cornu, the volva itself constitutes the large and well-developed 

 annulus. An annulus thus formed at the expense of the volva occurs 

 in a considerable number of species of Coprinus which, in that and 

 other respects, approach Lepiota, although differing in the colouring of 

 the spores ; an example is furnished by G. sterquilinus. The annulus is 

 in these cases prolonged with the peripheral tissue which encloses the 

 base of the frequently bulbous foot. An annulus of similar origin 



* See this Journal, ii. (1879) p. 917. 



t Verhandl. Bot. Ver. Prov. Brandenburg, xxii. (1880) pp. 107-8. See Bot. 

 Centralbl., vi. (1881) p. 37. 



X Bull. Soc. Bot. Franee, xxviii. (1881). pp. 28-34. 



