ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
623 
(5) The previous irregularities noticed on the addition of potassium 
arsenite to the yeast extract are probably to be explained by the proteids 
in the extract protecting the zymase from the action of the arsenite ; as it 
has been found that the dilution of the extract with water, in the presence 
of 2 per cent, of arsenite, practically stops fermentation, whereas dilu- 
tion with blood-serum or liquids rich in proteids, or even sugar solution, 
in the presence of the same amount of arsenite, retards the fermentation 
to a slight extent only. Glucose can also be fermented to a certain 
extent by yeast extract in the presence of arsenite. 
y. Genera]. 
Origin of the Leafy Sporophyte.* * * § — Prof. J. M. Coulter discusses 
the difficult question of the phylogeny of the leafy sporophyte. The 
tendency of his paper is to suggest that the Pteridophyta may have had 
an entirely different phylogenetic origin from the Bryophyta. “ The 
polyphyletic origin of similar structures,” e.g. the archegone of Mosses 
and of Ferns, “ and of similar groups, makes the problems of phylogeuy 
immensely more complex, but is probably much more consistent with 
the facts.” 
Effect of Arsenic on Plants.f — M. R. Bouillac enumerates a number 
of fresh-water algae which can absorb a certain amount of arsenic acid in 
the form of arseniates without injury, these salts partially taking the 
place of phosphates. The species referred to are Ulothrix tenerrima , 
Protococcus infusionum, Dactylococcus infusionum, and Stichococcus bacil- 
laris. With Schizothrix lardacea arsenic acid seems even to have a 
more favourable influence on the growth than phosphoric acid. 
Action of Roots on Granite. J — Sig. F. Sestini finds that the roots 
of many plants, especially those of Leguminos® and Gramme®, have a 
powerful decomposing effect on felspar, assimilating the alkaline bases, 
and all the ingredients which serve for the nutriment of the plant, 
leaving behind hydrated aluminium silicate. A similar part is also 
probably played by the microbes of the soil. 
B. CRYPTOGAMIA. 
Cryptogamia Vascularia. 
Prothallium of Lycopodium clavatum.§ — Mr. W. H. Lang describes 
the hitherto unknown prothallium of this club-moss. It is a nearly flat 
plate of tissue with numerous rhizoids, its structure closely resembling 
that of L. annotinum. Of seven prothallia examined, six were female 
and one male. No archegones were found on the latter ; but on two of 
the female prothallia a few antherids were seen. The archegones and 
antherids were both confined to the upper surface of the prothallium ; 
each organ is developed from a single superficial cell. In the young 
plant no structure was recognised comparable to the protocorm of 
L. cernuum. The large foot persists for a considerable time after the 
* Bot. Gazette, xxviii. (1899) pp. 46-59. 
f Ann. Agronomiques, 1898, pp. 561-602. See Bull. Soc. Bot. France, xlvi. 
(1899) p. 64. t Atti Soc. Tosc. Sci. Nat., Proc. Verb., xi. (1899) p. 138. * 
§ Ann. of Bot., xiii. (1899), pp. 279-317 (2 pis.). 
2 T 2 
