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1913] CURRENT LITERATURE 171 
character of the plant remains which compose it, and to a much less degree 
on the chemical and physical conditions to which it has subsequently been 
exposed. It is accordingly clear that the study of coal is to a very large 
extent within the domain of the biologist, for certainly no adequate concep- 
tion of the problem can be reached without his cooperation. 
here are a few slips on the part of the author; for example be states 
that anthracite and cannel differ from ordinary so-called bituminous coal and 
oil shale or boghead respectively, by the fact that they contain little or no 
ash. Obviously this statement does not generally hold of these types of coal 
as mined in North America. ARBER has confined his observations in this 
respect to European coals. His book is nevertheless planned on the broadest 
lines, and is commended to all who wish to obtain a clear conception of our 
present knowledge of coal.—E. C. JEFFREY. 
NOTES FOR STUDENTS 
Recent work in gymnosperms.—In 1910 Scott and MASLEN established 
the genus Mesoxylon to include certain paleozoic stems intermediate in struc- 
ture between Poroxylon and Cordaites, giving diagnoses of five species. One of 
these (M. Sutcliffii) has been described in detail by MASLEN,‘ and now two 
more species are described by Scott.’ The conclusion is reached that Mes- 
oxylon is “the last link in the chain of fossil types connecting the Pteridosperms 
with the typical Cordaites of the Upper Paleozoic,” being definitely distinguished 
from it only by the presence of centripetal xylem in the stem. A critical 
discussion of the ne of the new genera recently established by 
ZALESSKY is also give 
ts. THODAY nae Miss BERRIDGE‘ have made an anatomical investigation 
of the strobili of four — of Ephedra (E. altissima, E. distachya, E. fragilis, 
E. nebrodensis). The “clearly bifid” stamen of the three last named species, 
each half bearing four bilocular synangia, is traced into other species in which 
the bifid character is not evident, but in which there are fusions of synangia 
into trilocular or even quadrilocular synangia, until E. altissima is reached 
with only two bilocular synangia. A oe series is ales traced from the 
staminate disk of Cycadeoidea, through other itales, to Ephedra, 
where the disk is reduced to two segments, each nines two pairs of bilocular 
Synangia, and to Welwitschia, with its disk of six segments bearing trilocular 
Synangia. It is also discovered that the solitary ovule of the species investi- 
gated is the product of a fusion of the two ovules of the biovulate species, since 
4 Rev. in Bor. Gaz. 522326. 1911. 
’Scorr, D. H., The structure of oe — Lomaxii and M. poroxyloides. Ann. 
Botany 26: 1011-1030. pls. 87-90. 1 
°THopay (SyKEs), Mary rage = Berriwce, Emtty M., The anatomy and 
morphology of the inflorescences and flowers of Ephedra. Ann. Botany 26:953-985. 
Sigs. 21. pl. 85. 1912. 
