Algce as Geological Guides. — Tames, 95 
but enough evidence remained to enable me to refer the specimen with- 
out doubt to Taxus baccata L., var. canadensis Gray. 
This species has hitherto proved a somewhat common one in the 
interglacial of Canada, particularly in the Don valley.* 
No. 3. Quercus obtusiloba Michx. 
Specimen No. 3 showed considerable alteration. While in transverse 
section the quercic characters are well defined, in longitudinal sections 
the structural markings were almost obliterated. The resemblance of 
this wood to modern oaks was found to be most marked in the case of 
Quercus obtusiloba Michx., to which I therefore refer it, provisionally. 
This is the first time an oak has been found in the interglacial of Can- 
ada. 
Quercus obtusiloba is now found in southern Ontario, and particularly 
about the bay of Quinte (Macoiin). 
ON THE VALUE OF SUPPOSED ALG^E AS GEO- 
LOGICAL GUIDES. 
By Joseph F. James, M. Sc, F. G. S. A., etc. 
[Read before Am. Asso. Adv. Science, August, 1893.] 
In the discussion of the evolution of the vegetable king- 
dom it has been the habit to refer to the Algae as appearing 
very early in time, and as furnishing one proof of the theory 
of derivation and descent from the simple to the complex. fn 
the pursuance of this one writerf has given the number of the 
species of Algae that have been found in various strata, and 
has constructed a chart showing their gradual increase from 
early to recent times. Other writers have placed groups of 
rocks in the same time epochs upon the presence of certain of 
these organisms, while still others have gone so far as to make 
new genera for fossils because they occurred in a different I" 
cality, and were of a different geological age, and because 
they did not believe that Alga' could persist through the 
requisite time interval. The new genera are made, notwith- 
standing they resemble each other so much that, were they 
found in the same beds, or even in the same horizon, they 
would undoubtedly have been placed in 6he same genus. 
It has now come to be well recognized that Algae existed at 
a very early period in the history of the earth. The abun- 
*The Pleistocene Flora of Canada, Bull. Ceol. Soc. Am., i, 321. 
+ Ward,L. F. Sketch of Paheobotany. Fifth Ann. Rept , U.S. < ieol. 
Sur., 1885. 
