


tgor] CURRENT LITERATURE 283 
in great detail the stratigraphic succession of the fossil floras of the Pottsville 
formation in the Carboniferous of Pennsylvania.—A. C. SEWARD, whose 
study of the fossil history of Gingko has been briefly noted in this journal 
(30: 139), has published on the Wealden flora of Bernissart (Mem. Mus. 
Roy. Hist. Nat. Belg., 1900); the ferns dominate in these beds rather than 
cycads, but there are no angiosperms, although the Wealden is commonly 
regarded as equivalent to the Potomac beds of our country.—GRAND ’EuRY 
has given some very interesting accounts (Compt. Rend. 130: 871, 988, 1167, 
1366. 1900) of the Carboniferous forests of France. By his study of the 
plants preserved zm sztu, he concludes that most of the Calamites and some of 
the tree ferns grew in the water; the herbaceous ferns probably grew largely 
on hummocks. Even Cordaites seems to have grown in swamps, and 
Grand ’Eury suggests analogies with Taxodium and the Dismal swamp of 
today. The prevailing horizontality of the roots strikingly suggests swamp 
habitats. The author doubts if we have evidence of upland vegetation.—At 
the last meeting of the British Association (Geol. Mag., Jan. 1901) Seward, 
Kidston, and others discussed Carboniferous conditions, as indicated by plant 
fossils. Little new material was added, though Seward suggests that the 
xerophytic structures of Carboniferous plants may perhaps be accounted for 
by swamp habitats.—PENHALLOw (Brit. Assoc. Adv. Sci., 1900) has made 
an interesting report on the flora of the Canadian Pleistocene. Interest was 
aroused a few years since by Coleman's discovery of the papaw and osage 
orange in interglacial beds near Toronto, indicating a genial climate between 
ice-sheets. Over eighty Pleistocene species are now known from Canada. 
As Knowlton suggests in discussing this report in Pant World for January, 
there is a wide field for work in the study of Pleistocene floras in America. 
The poverty of our information in this respect is in striking contrast with the 
wealth of knowledge as to the Pleistocene of Europe—H. C. COWLE 
E FORMATION OF TETRADS has lately been investigated by H. O. 
Juel.“° The contribution consists of three distinct papers which may be con- 
sidered separately. ; 
I. Tetrad formation in the ovule of Larix.—The general relationships 
between the reproductive organs of pteridophytes and spermatophytes have 
long been known, but while it is accepted that the pollen grain arises by a 
tetrad division, just as the spores of pteridophytes, it is generally believed 
that the megaspore of spermatophytes is formed without such a division. 
development of the mother cell of the megaspore to the beginning of endo- 
Sperm formation. The paper is of special interest as the first to treat this 
portion of the life history of a gymnosperm from the standpoint of modern 
**Beitrage zur Kenntniss der Tetradenbildung. Jahrb. f. wiss. Bot. 35 : 626-659, 
bls. 15,16. 1900. 
