A454 Scientific Intelligence. 
goes to prove, that the portion of assimilated sap which is not used for 
nutrition on the way to the root, runs back to the wood through these 
horizontal medullary rays; and thus the sap describes a kind of circle, 
not, indeed, in determinate vessels, but in a definite path leading 
through the different parts of the plant. It is difficult to conceive how 
in recent times the results of these experiments could have been ques- 
tioned, and the existence of the descending current in the bark denied. 
which the sap contained in the upper part of the plant must soon be- 
come greatly concentrated and potential for development (Schleiden, 
nation may be received as satisfactory.” (p. 70,71.) After some ex- 
cellent oe of criticism, Moh! ce that the discovery of en 
ot fully solved the problem of the movement of the sap in 
plants, sithough f in all probability it dots play an important, and i 
‘the question, whether plants live on inorganic food alone, or take in 
also organic matters, Mohl gives a sensible answer, rejecting the ex- 
treme view of Liebig, while still fully recognizing the great office and 
result of vegetation. (p. 78.) According to , Moh hl, , however, it is proved 
that plants do not absorb the carbonic acid diss al ved in water with the 
latter by means of their roots, (p. 81); but this seems hardly reconci+ 
lable with several facts stated on the next page, from which it is justly 
concluded that carbonic acid is carried up with the ascending sap into 
the leaves. From the fact that plants perish so soon in air deprived of 
all.oxygen gas, that sensitive leaves lose their irritability under such 
circumstances, &c., Mohl concludes, apparently with good reason, 
the absorption of oxygen and the exhalation of carbonic acid i in plants 
he life of 
described by Schuhz; i is = positively canihes to take afer in en ‘dh bj ‘ 
except as pr y mechanical causes. That the milky 
juice is not a trent iaatesah still less the nutrient juice, is @ 
manifest. (p. 
cell as an organ of propagation is treated, first a 
multiplication of plants by division ; second, by ici 
seeds. The n of certain Confervoid Alga, such as 4y$' 
is said to bear no analogy to sexual reproduction (p. 113); @ conclusion 
which may be questioned. A good summary is given of the of 
known respecting the free and spontaneous movements of the spores 
