878 NOTICES OF BOOKS AND MEMOIRS. 
traversed by other air- and light-, or water- and food-seeking 
organs of like nature 
The 
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before the reader the mode by which a creeping stem wriggles = 
way amongst dense herbage, and at the same time aids im 
Seeenine § the m aera ip writhings of the rootlets beneath. 
“Some of the periodic movements of leaves have been known for 
many » ars, ee in some cases for centuries; but the authors 
bring vidly be bef s the fact that so many leaves describe more 
or os ipirendieoen elliptical prone that we must believe that all 
leaves circumnutate—not always regularly, but more or less 
ecide a large rection of examples the swing of the leaf is 
inereased periodically with the waning light of evening, or as the 
morning; the leaf moves its apex towards the 
zenith in the evening, and falls towards the horizon next morni ng. 
But some leaves describe pee approaching the circle, and all 
stages _ transition are fou 
Some climbing plants are typical of the one extreme, their 
stems sw. Wisk in nearly “pone sweeps; certain leaves are so far 
ellipses which these courses really consist of. The reason that the 
circumnutation of climbing stems has become so regular and 
circular is, that the sweeping internodes may swing over a larger 
area and stand a better chance of meeting with a support. But 
what reason can we assign for t drawn up and down 
movements of leaves? The authors cage because there is some 
benefit derived by the leaf from a vertical position at night, 
as opposed to a.more or less eorinodita isting during the ar 
If they can demonstrate this, we have to admit that such m 
nencen of ¢ circumnutation might be increased by natural sohbet 
us We are papeccnes anew to ere beautiful aggre 
Messrs. Dares that if a dospilie Teaf j is prevented from assuming 
its normal position on a clear, chilly “oe by i fastened so 
that the upper surface is exposed to direct radiatio certain 
amount of injury follows, varying in different guns some 
