422 BOTANICAL GAZETTE [MAY 
and very shortly after the oesees the vegetation of the world experienced 
a very remarkable transformation 
WIELAND” has investigated the saviiieataitied fossil Cryptozoon, and the 
much discussed question of the origin of the oolites. Oolites and Cryptozoon 
are said to be notable features of the Ozarkian. According to WIELAND, 
Cryptozoon is a marine alga ‘‘ which formed vast reefs in the Ozarkian oceans’’; 
and in connection with a description of a new species of Cryptozoon from Penn- 
sylvania, and the general occurrence of similar forms (as Eozoon, for example) 
in the early Paleozoic, he concludes that the hypothetical “age of seaweeds” 
preceding the coal plants is a reality. 
Berry* has contrasted the ancestry of our present walnuts and hickories, 
so far as they can be recognized as fossils, back to the Middle Cretaceous, and 
presents evidence that at this remote period ot geographical range and their 
abundance were much greater than now. evidence also enables him to 
explain the Sars) distribution of ae Tiving representatives of the 
family.—J. M 
Slope-direction and forest distribution—TuRESSON* points out that 
Pseudotsuga taxifolia (Douglas spruce or red fir) is confined to north-facing 
slopes in the Spokane region in eastern Washington. He says ‘“‘the evidences 
have shown that exposure is the regulating factor in the distribution of the tree 
in this region, the northern slopes and ridges being the only localities which 
offer the needed humidity in soil and atmosphere.” He adds “not only around 
Spokane but in all more or less arid regions can this be observed.” He cites 
from his own observations and from literature several instances illustrating 
the fact that the southern slope tends to be more xerophytic than the northern. 
After calling attention to the fact that this tree reaches its best development in 
the Puget Sound region, he cites CowLEs” to indicate that near its areal limits 
a species “can grow only in those formations which resemble most closely in 
an edaphic way the climatic features at the distribution center.” Speaking 
of the distribution of this tree in the San Juan Islands, he calls attention to the 
sine in climate between these islands and the Spokane region. He then 
says “it is not surprising to find Pseudotsuga taxifolia confined to the northern 
slopes of the hills in these islands.” Quoting from a paper by the reviewer, 
* WIELAND, G. R., Further notes on Ozarkian seaweeds and oolites. Bull. Amer. 
Mus. Nat. Hist. 33:237-360. pls. 14-19. 1914 
°° Berry, Epwarp W., Notes on the jaded history of the walnuts and hick- 
ories. aA Report for 1913. PP. 319-331. 1914. 
** TurEssON, G., Slope exposure as a factor in the distribution of Pseudotsuga 
taxifolia in eastern Washington. Bull. "Pont. Bot. Club 41:337-345- 1914- 
27 COWLE , The physiographic ecology of Chicago and vicinity. Bor- 
Gaz. — fan aan TgOT. 
., Forest distribution in the San Juan Islands: a preliminary note. 
ign World x6: es 1913 
