THE JOURNAL OE BOTANY 
36 
the cups may be clue to some small extent to excretion from the 
plant itself. This seems the more probable in that, during active 
growth, the stem of the plant is gorged with a colourless slightly 
viscous sap, which appears to be under some pressure ; for directly 
the stem is cut, it oozes copiously from the pores, as Boyer observed. 
This conclusion seems to be confirmed by the fact that on 
18th June 1921, when examining a number of teasels growing in the 
huge chalk-pits at Grays Thurrock, Essex, I noticed that nearly all 
the cups of those which grew among grass and hushes on a steep 
chalk slope contained a little liquor, while all the cups on other 
plants growing in the open, on the bare and drier floor of the pit 
exposed to the sun, were empty or practically so. As this was during 
a period of very exceptional drought (onl} r 3’91 in. of rain having 
fallen there since the 18th January, a period of 22 weeks*), it seemed 
remarkable that any of the cups should have held any water at all. 
It seemed clear, therefore, that the small amount of water met with 
must (unless derived from dew) have been excreted by the plants 
themselves : in which case it must first have been absorbed by their 
J (/ 
roots from the chalk in which they grew. Now chalk retains at all 
times a certain amount of moisture ; and that the plants growing 
among grass and bushes should have held more water than those 
growing in the open was due, no doubt, to the fact that chalk 
covered with herbage would retain more moisture than chalk exposed 
to the full rays of the sun, which had been very hot for some weeks 
previous to the date named. Five weeks later, on 25 July (there 
having been no more than (H)S in. of rain in the interval, making 
!’l ins. only in 27 weeks*), all cups were absolutely dry! 
The water which gathers in the cups of the Teasel may very 
likely serve to succour the plant in time of drought, by being absorbed 
(perhaps in part re-absorbed) into the tissues of the plant, as has 
been held by many who have written on the subject. Thus, in 1789, 
Erasmus Darwin (/. c.) wrote that it “ serves .... for the nutriment 
of the plant in dry seasons.” Pfeifer, more cautious, says (Physiol. 
Plants, transl. A. W. Ewart, i. 160; 1900) that “a little of the 
water collected .... may be absorbed, although these plants do not 
normally require any supply of water from this source.” Kernel- 
(Nat. Hist. PI. i. 210) also expresses doubt whether the water col¬ 
lected is absorbed to any great extent. Barthelemy reached, how¬ 
ever, a totally different conclusion {op. cit. 609) ; plants the cups of 
which he kept empty of water attained (he says) no more than a 
third or a quarter of their normal height and their lateral shoots 
failed to develop. He declares explicitly that “ beau joue un role 
considerable dans la phase du vegetation de cette plante ” ; and his 
conclusion seems justified, so far as it goes, though there may be 
another interpretation of the evidence on which he relies. On the 
other hand, Boyer denies altogether that the water nourishes the 
plant {op. cit. 617) : “ Le sejour de l’eau dans les feuilles est sans 
influence sur la vegetation des Dipsacus. Un Dipsacus dont je 
* For those figures, I am indebted to the kindness of Mr. A. C. James, 
M.Inst.C.F., of Grays. 
