3876 NOTICES OF BOOKS AND MEMOIRS. 
these result in slight movements of the tissues — up by the 
cells, we have the foundation for series of phenomena produced by 
qpulikfeatione of the original movement, by the strat of physical 
and other agents of ‘ile hii and if the movements thus 
rendered are advantageous i may be amplified by natural 
selection. The chief object of the present work is to describe and 
connect ibe several large classes of movement common to 
almost all p. 
After a op sey egrenmigt _ occupied with clear definitions 
of useful terms, the anthors at o lunge into a series of detailed 
observations, proving that ane tuidinlde; hypocotyls, and epicotyls 
of the young seedlings of numerous plants are —— engaged in 
circumnutation ; the clever way in which each part is made 
write an pproximate history of its own movements, either with a 
bristle, &e., on smoked glass plates, or with a ray of light on the 
descriptions and frank statements of partial failures, do we learn 
how to experiment and record. 
A e and varied number of seedlings of phanerogams, one 
Fern, and one ot ag lla are proved to be in constant circum- 
nutation ; and we may ripceard safely accept the conclusion that 
a same is pi for all plants, some more an I 
P 
proceeds, and to see that some benefit may accrue to the infant 
plant, as its radicle seeks to screw and wriggle its tip into the soil; 
the insumation becoming completed by the force of growt 
length and breadth. The authors even attempt to measure this 
seedling (commonly arched to give more purchase, and to wi Ww 
the cotyledons with as little hesieea as possible) lifts up the load 
of soil above, and wriggles through to light and air. We cannot 
but pass on to consider the important discoveries enunciate 
Chap. iii. When the tip of a radicle meets a solid obstacle, it iss 
not Ghatiliataly press upon it and try to force itself through to its 
own festruetes: but, as the authors observed, ‘the delicate root- 
cap, when i t first touched any directly opposing surface, was a 
little coche Se tranaversely ; the. flattening soon became oblique, 
and i few hours quite disappeared, the apex now pointing at 
right ‘angles to its former course. The radicle then seemed to 
gli its new direction over the surface which had opposed it, 
pressing on it swe very little force.” The authors did not think 
this due to mere mechanical resistance, for the pressure was too 
slight; and it i is rp tlenuae that the growing tip of a radicle is more 
rigid than the parts just above, which have ceased to grow 
Besides, a very yielding object—e. y., thin tin-foil—will defies the 
rigid tip of the radicle. The effects could not be due to a mere 
owing of growth at the point of contact, since the curvature 
