NOTES AND MEMOBANDA. 147 



cipient apparatus had gone. It is an interesting circumstance that the 

 optic nerve of Cliernes seems to have, in some degree, taken on the 

 function of a nerve of common sensation, since many of its fibres are 

 distributed to the layer of connective tissue underlying the hypo- 

 dermis. 



In one individual of the same species a curious malformation 

 occurred, there being a single eye m the middle line of the cephalo- 

 thorax, instead of the usual pair. The organ in question had a slightly 

 convex cornea, divided into hexagonal areas ; beneath this was a layer 

 of crystalline rods, and a strongly developed layer of brown pigment. 

 This thoroughly well-formed visual organ is supplied by both optic 

 nerves, which, after leaving the brain, ran forwards parallel with one 

 another, to the layer of crystalline rods. 



Two cases of abnormal organs of sight were also met with in 

 Chelifer ixoides. In one of these the eye on one side was perfectly 

 normal, but on the other, while the nerves and bacillary layers were 

 well developed, the cornea formed a mere speck, like the eye-spots of 

 Chernes. In the second instance, both eyes were developed, but were 

 so small as to be hardly visible ; the crystalline rods and pigment, at 

 the same time, were much reduced. 



Ascent and Circulation of the Sap. — The course and the causes 

 of the ascent and circulation of the sap in plants are attracting much 

 attention just now among French physiologists, and the results should 

 be carefully studied in connection with the recent researches of M. 

 Boussingault and the Rev. G. Henslow as to the power of leaves to 

 absorb water in the fluid or gaseous state. A recent number of the 

 botanical series of the ' Annales des Sciences Naturelles ' * contains 

 three articles bearing more or less directly on this subject. In the 

 first of these, " On the Influence of the Temperature of the Soil on 

 the Absorption of Water by the Eoots," M. J. Vesque arrives at the 

 following general conclusions: — 



1st. In no case can absorption be practically separated from trans- 

 piration, in a plant imder normal conditions. As soon as the absorp- 

 tion exceeds the transpiration, the former diminishes, and is probably 

 regulated by the latter; when the transpiration is suppressed, the 

 absorption gradually lessens, and finally ceases. The reason of this 

 phenomenon doubtless lies in the manner of behaviour of the air 

 within the plant. The transpiration ceasing to make a vacuum, there 

 comes a time when the atmospheric pressure, plus the pressure from 

 the roots, is incapable of overcoming the tension of the internal air 

 and the resistance of filtration. 



2nd. When the temperature of the soil is rapidly raised, absorp- 

 tion diminishes in consequence of the increase of the pressure of the 

 air contained in the wood. For the same reason, absorption increases 

 when the temperature of the soil is rapidly lowered. 



3rd. Each temperature of the soil being considered as a constant, 

 the absorption increases with the temperature ; except perhaps in high 

 temperatures, where the question has not yet been completely worked 

 out. 



* 'Ann. cles Sci. Nat.' (Bot.), 3rcl ser., vol. yI. (1878) p. 169. 



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