The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1869-08-03
Scientific Notes.

ACTION OF THE CUTICLE OF PLANTS. M.
Barthelemy has applied the principle of
osmosis in explaining plant respiration. In
plants there exists a cuticle which has a
chemical composition and physical constitu-
ton somewhat resembling caoutchouc. 1t is
not found at the stomata on the under sur
face of leaves. As the exhalation of the
oxygen is greatest when sunlight falls on the
upper surface of leaves, Barthelemy explains
this by supposing that the respiration takes
place through the cuticle of the upper surface,
while the stomata or pores of the under sur
face perhaps absorb only nitrogen.
HEARING ORGANS OF CRUsTACEA. John
Lubbock in discoursing on Crustacea, says:--
We do not understand how they see, smell, or
hear; nor are entomologists entirely agreed as
to the function or the structure of the anten-
nae. Thisinteresting subject offers amostpro-
missing field for study, and Iwould particularly
call the attention of entomologists to remark
able memoir by Hensen, on the auditory
organ in the decapod Crustacea. Hensen has
shown that the otolithes in the open auditory
sacs of shrimps are foreign particles of sand,
! introduced into the organ by tie dHtR1dL ITSELF
He proved this very ingeniously by placing a
shrimp in filtered water, without any sand,
| but with crystals of uric acid. Three hours
after the animal had moulted he found that
| the sacs contained many of these crystals.
the auditory sac is susceptible of being thrown
into vibration by particular note, which is
probably determined by the length and thick
ness of the hair. 1t may be experimentally
shown that certain sounds throw particular
hairs into rapid vibration, while those around
them remain perfectly still.
DOUBLE REFRACuoN. Professor Tyndall,
in recent lecture 'On Light, at the Royal
Institution of London, thus very clearly ex-
MI ha Of
according to the theory that all luminous
effects are the result of undulations of a
highly attenuated and subtle fluid which per-
vades all space and permeates all pOnderable
matter: In air, water, and well-annealed
glass, luminiferous ether has the same elias.
ticity in all directions. There is nothing in
the molecular grouping of these substances tc
interfere with the perfect homogeneity of the
ether. But when the water crystalliZes to ice
the case is different; here the molecules are
constrained by their proper forces to arrange
themselves III certain determined manner
They are, for example, closer together in some
directions than in others. This arrangement
T of the molecules carries along with it an ar
rangement of the surrounding ether, which
causes it to possess different degrees of elias
ticity in different directions In a plate OF
ice, for instance, the elasticity of the ether il
a direction perpendicular to the plane OF
e freezing, is different from its elasticity in q
o plane parallel to the same surface. This diff
: ference is displayed in striking manner b,
Iceland spar, which is crystallized carbonate
!, of lime and in consequence of two differen
S elasticities, wave of light passing througl
}, the spar is divided into two-the one rapid
il corresponding to the greater elasticity, AM
the other slow, corresponding to the lesse
elasticity. Where the velocity is greatest, tn
b" refraction is least, and where the velocity
n least the refraction is greatest. Hence in Ice
r, land spar, as we have two waves moving wit
e different velocities, we have double refra,
&c ton. This is also true of the greater numbC
!, of crystalline bodies. If the grouping of tn
u molecules be not in all directions alike, th
q ether will not be in all directions equal
p elastic, and double refraction will infallibl
70 result.