537 
was previously indicated by the internal antidromy of Liguidam- 
bar. J may add that the flowers on one plant of Hibiscus Syriacus 
show a tendency to twist in relatively opposite directions; and 
though the phyllotaxy of that species is not easily determined 
(the right and left spirals being almost similar), yet in some cases 
Opposite orders of spirality can be found on neighboring branches. 
My friend, Prof. F. E. Lloyd, informs me that in the cycada- 
ceous species Encephalartos Altensteinu he finds the cones on the 
Same tree relatively antidromic. This accords with the condition 
of the allied coniferous order. 
PRINCETON University, November 3, 1896. 
Reviews. 
Some Analogies in the Lower Cretaceous of Europe and America. 
Lester F. Ward. Reprinted from 16th Ann. Rept. U. S. 
Geol. Survey, Part I., 1894-1895 [ Washington, 1896], pp. 
463-542. Plates xcvit.—cvitt. and illust. in text. 
This important contribution is of interest to both the botanist 
and the geologist on account of the use which is made of palaeo- 
botanical evidence in the correlation of geologic horizons. The 
comparisons are chiefly made between the Potomac formation 
of America and the Wealden of Europe, and the author has taken 
a very broad and liberal view of what should be included under 
the latter, giving it a wider range at each extremity than is usually 
conceded to it. In this connection a plea is made for dual no-. 
menclature in geology, according to the point of view from which 
observations are made. From the standpoint of fossils alone the 
Wealden would be restricted to narrower limits than if considered 
Stratigraphically, that is from the standpoint of origin and manner 
of deposition of sediments. 
Stratigraphically the Wealden would have to include part of 
what we have usually regarded as Jurassic with some of the lower 
Cretaceous. ‘The method of formation and lithologic characters of 
the Wealden, as thus defined, evidently correlate it very closely 
with our lower Potomac formation, that is to say the strata are 
largely of estuary or fluviatile origin and consist of alternating sands 
