use wall. It should be
recorded that Sir W. Thiselton-Dyer {137a} planned a similar arrangement
independently of Hales, and found it produced a marked improvement of the
well-being of the plants.

It is worthy of note, that though Hales must have known Malpighi's theory
of the function of leaves (which was broadly speaking the same as his
own), he does not as far as I know refer to it. In his preface (p. ii.)
he regrets that Malpighi and Grew, whose anatomical knowledge he
appreciated, had not "fortuned to have fallen into this statical {137b}
way of inquiry." I believe he means an inquiry of an experimental
nature, and I think it was because Malpighi's theory was dependent on
analogy rather than on ascertained facts that it influenced Hales so
little.

There is another part of physiology on which Hales threw light. He was
the first, I believe, to investigate the distribution of growth in
developing shoots and growing leaves, by marking them and measuring the
distance between the marks after an interval of time. He describes (p.
330) and figures (p. 344) with his usual thoroughness the apparatus
employed; this was a comb-like object made by fixing into a handle five
pins .25 inch apart from one another; the points being dipped in red-lead
and oil, a young vine-shoot was marked with ten dots .25 inch apart. In
the autumn he examined his specimen, and finds that the youngest
internode or "joynt" had grown most, and the basal part having been
"almost hardened" when he marked it, had "extended very little." In
this--a tentative experiment--he made the mistake of not re-measuring his
plants at short intervals of time, but it was an admirable beginning, and
the direct ancestor of Sachs' {138a} great research on the subject. In
his discussion on growth it is interesting to find the idea of
turgescence supplying the motive force for extension. This conception he
takes from Borelli. {138b}

Hales sees in the nodes of plants "plinths or abutments for the dilating
pith to exert its force on" (p. 335); but he acutely foresees a modern
objection {138c} to the explanation of growth as regulated solely by the
hydrostatic pressure in the cell. Hales says (p. 335): "But a dilating
spongy substance, by equally expanding itself every way, would not
produce an oblong shoot but rather a globose one."

It is not my place to speak of Hales' work in animal physiology, nor of
those researches bearing on the welfare of the human ra