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NATURE NOTES 
thing for aliment or defence, what is redundant passes out 
into the bark, so to the root, and thence to the earth again, 
and thus a circulation is effected.” 
It is interesting to note here what modern science has 
substantiated, and what rejected ; there is, of course, an upward 
current of sap from the roots, and there is a grand assimilation 
and synthesising of organic compounds going on in the leaves 
and other green parts ; and there is a descending current — but 
this is of assimilated products, and therefore not the waste 
sap of Miller, but a rich nutritive sap ; and finally, of course, 
the notion of excretion of waste products through the roots is 
simply an error derived from the attempt to press analogies to 
animal organisation. As a matter of fact, the waste substances 
are deposited in the bark, in laticiferous vessels, in falling 
leaves, and so on. 
Then follows an extremely interesting passage : for, regarding 
the course of the sap, Miller adverts to the opinion that it 
descends by the larger fibres in the bark, placed immediately 
over the wood ; “ in which descent the sap, now sufficiently 
prepared, adds a part of its substance to the contiguous wood 
and thus increases by apposition." Now considering the controversy 
of modern times as to whether growth takes place by intus- 
susception or by apposition, and the strong evidence adduced 
for the existence of the latter process after Nageli had established 
intussusception as the mode of growth, it is, I think, very 
interesting indeed to find this old botanist quietly assuming 
apposition as the mode of increase — a view to which modern 
botany has in great measure returned. Of course it is very 
possible that Miller’s views of growth by apposition were exceed- 
ingly crude and vague, and that he understood thereby something 
far grosser than do we — but, on the lowest ground, it is interest- 
ing to find this most modern watchword of botanical controversy 
cropping up in a work one hundred and fifty years old. 
The unimportance and gradual disappearance of the pith is 
correctly explained ; and then we are treated to Dr. Boerhaave’s 
division of plant-juices into six classes. The first class, it seems, 
comprehends the crude nutritious juices of the root and stem, 
which are a “ sub-acid watery lymph,” and for examples we are 
referred to the juices which issue from wounds made in the 
woody parts of plants, as, e.g., the “tart liquor issuing from the 
root of the walnut-tree when cut off in May ” ; and we are 
presently told, too, that such juices may be esteemed “as yet 
fossil, being generated of, and in, the earth.” Here, now, I must 
take the opportunity of drawing attention to later work, which 
shows how investigators may be on the verge of a discovery, 
which yet is deferred for more than a century. Readers of Pro- 
fessor Vines’ “ Physiology ” will remember the important chapter 
in which he explains the solution of the food- matters in the soil 
by the erosive action of an acid cell-sap excreted by the roots : 
experiments of Sachs and others are quoted, but the discussion 
