1893.] Anatomical and Physiological Researches. 313 
among the earth-particles. Experiments on the growth of 
the roots of Solanum tuberosum showed how the root-system of 
this plant, when the surroundings are arranged similar to 
those of an epiphytic vegetation develops in a way like that 
ofa genuine epiphyte. The property of doing so is, as long 
as the roots live under ordinary circumstances, latent, the 
adaptation to surroundings giving rise to this new feature of 
root-life. The facts thus obtained are used by Sachs to ex- 
plain saltatory biological variations, one of the features of the 
“struggle for existence.” Those who explain each and every 
property in an organism by the proper selection of species 
forget that we had the properties, irritabilities, and energies of 
the organs before the selection, or, at least, we ought to 
search for them. What we understand as the original prop- 
erties of the organized matter, is not told by anybody, but 
Sachs is sure, ‘that certain properties, irritabilities, etc., were 
originally present, on which the struggle for life, and the na- 
tural selection could exert its influence.” 
; It is very interesting to see how Sachs, in the autumn of his 
life holds up again experimental physiology before a 
school of biologists which too often makes deductions con- 
seming general biological laws, adaptations, etc., from facts 
ust as they find them and which does not trace these facts 
'o their origin by means of experiment.—J. CHRISTIAN BAY. 
Studies upon the Xyridez. 
and very j 
we ne Nesetative organs show morphological characters that 
also of UY Useful in the discrimination of species, but are 
point aig interest when considered from a comparative 
*Nitssoy Se RF nn cognate ; oe 
Haig, yyy, AUBERT: Studien fiber die Xyrideen. Kgl. Svenska Vet. Akad. 
RO. 14. pp. 75 pl. 6. Stockholm 1892. 
on em 
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