ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
775 
Gymnosperms, or the endosperm of Angiosperms, than it does the 
prothallium of any pteridophyte (except possibly Selaginella). In the 
multiciliate antherozoids, and in the absence of a suspensor, Isoeles 
resembles ferns rather than lycopods ; the body of the antherozoid is 
derived, as stated by Guignard, from the nucleus of the mother-cell. 
The microspore produces, on germination, a single prothallial cell, 
and an antherid composed of four peripheral and four central cells ; 
each of the latter gives rise to a single antherozoid. The process of 
cell-division in the ripe megaspore is entirely similar to that in the 
embryo-sac of most Phanerogams. The first archegone arises from one 
of the first-formed cells, at the centre of the apical region. The 
prothallium is incapable of independent growth, and dies after the supply 
of food in the spore is exhausted. More than one archegone may be 
fertilized, but the complete development of more than one embryo has 
not been observed. The secondary thickening of the stem is of a different 
type from that in Gymnosperms and Dicotyledons, approaching more 
nearly that found in a few Monocotyledons. The author’s results differ 
in some respects from those obtained by Farmer * in the case of 
1. lacustris. 
Sieve-tubes of Filicinese and Equisetineae.t — M. G. Poirault dis- 
cusses the characteristic differences between the sieve-tubes in Phanero- 
gams and those in Cryptogams. The modification which occurs in the 
latter consists principally in the fact that while the punctations of the 
membrane are open in Phanerogams, in Vascular Cryptogams they are 
always closed. Janczewski has also stated that in the former we have 
callus, which is absent in the latter ; the only exception to this rule 
being P ter is aquilina , in which we find callus, as in Phanerogams. 
M. Poirault does not, however, agree with Janczewski in this point, 
having found callus in Ferns, Marattiaceee (?), Equisetaceae, and Hydro- 
pterideae, the only exception being the sieve-tubes of Ophioglossaceae. 
The author does not insist on the absence of a nucleus and the presence 
in the tubes of numerous granules ; and on this point his observations 
agree absolutely with those of Janczewski. 
Nectaries of Pteris aquilina. :f— Herr W. Figdor describes the 
nectariferous organs of the common brake, which are found at the base 
of the pinnae of the first or second order. When young they form 
triangular projections, which gradually become flatter. Their surface is 
distinguished from that of the rest of the axis by being quite glabrous, 
and is usually reddish. The cells of the nectar-gland are about the 
size of those of the ordinary fundamental parenchyme, and are often 
separated by intercellular spaces. They are furnished with stomates, 
some of which appear to possess the ordinary function, while others 
serve for the excretion of the saccharine fluid. Beneath the nectary is 
the end of a vascular bundle. Its cells contain a large nucleus, few 
chlorophyll-grains, and a number of larger or smaller strongly refringent 
granules ; those at the margin also contain anthocyan. With increasing 
age the nectaries become functionless. 
* Cf. this Journal, ante, p. 376. 
t Comptes Rendus, cxiii. (1891) pp. 232-4. 
i Oesterr. Bot. Zeitschr., xli. (1891) pp. 293-5 (2 figs.). 
