THE COMMON TEASEL AS A CARNIVOROUS PLANT 
35 
of rather over half-a-pint each plant. Unfortunately I neglected to 
note the number of water-cups borne by each individual plant; had I 
done so, it would probably have explained why the quantity of water 
per plant bore, as will be seen, no regular relation to the height of 
the plant. 
Erasmus Darwin’s statement, made nearly a century and a half 
ago (Bot. Grard. ii. 30 n. ; 1789), that “There is a cup around every 
joint of the stem of this plant, which contains from a spoonful to 
half-a-pint of water,” is incredible, if he means (as apparently he 
does) that any single cup is capable of holding the last-named 
quantity. Much more nearly correct is the estimate of Sir Francis 
1) arwin, who says (Q. Journ. Microscop. Sec. xvii. 269; 1877) that 
the cups hold “from 12 to 100 cc. of fluid,” the larger quantity being 
equal to about one-sixth of a pint; which, reckoning three cups to a 
plant, agrees approximately with my own observations given above. 
Barthelemy has stated ( Comptes-rendns Acad. Sci. lxxxvii. 1878, 
p. 609) that the cups of the var. fullonum are larger and more 
numerous than those of Z). sylvestris. On one plant of the former, 
1 m. 60 cm. high, he counted 15 cups, which contained 280 grammes 
of water; and he estimates that a fine plant when in perfection might 
hold from 300 to 350 grammes. 
The source of this water has been investigated by French botanists. 
As long ago as 1863, Charles Boyer made observations (Bull. Soc. 
Bot. France, x. 746; 1863) on plants growing in his garden at 
St. Bemy, near Montbard; but his results are not very conclusive. 
“ L’eau s’amasse la nuit,” he declares ; adding that the quantity 
accumulated during one night, by excretion from the plant itself, 
might be from half to one-fifth of the capacity of any cup, the 
amount varying according to the position of the cup. The sun and 
wind cause, he says, considerable evaporation of the liquor. His con¬ 
clusion is “ que la secretion joue le principal role dans la production 
de l’eau, et que la rosee n’v contribue guere que pour un huitieme. 
Le siege de la secretion doit etre dans les tiges, puisqu’elle persiste 
apres l’ablation de la presque totalite du limbe des feuilles. Pendant 
la periode de grande vegetation, la tige est gorgee de seve, qui, sous 
forme de goutelettes, s’echappe a l’instant de la moindre blessure.” 
Fifteen years later, A. Barthelemy {op. cit .), as a result of obser¬ 
vations extending over several years, arrived at conclusions totally 
different from those of Boyer. The cups of some plants he grew 
under cover remained dry; from which he concludes that the water 
is due neither to dew nor to secretion from the plant itself, but is 
provided by the rain alone. He had watched plants during heavy 
rain and had seen the water gathering rapidly in the upper cups; 
then overflowing their capacity; next, trickling down the stem ; and 
finally filling the lower cups. The latter are filled in the same way 
from the upper cups when the plant is shaken during a high wind. 
There can be no doubt, I think, that in the main Barthelemy was 
right; for I have notes that on 6 June 1882 and 3 July 1883 1 found 
the cups exceptionally full immediately after heavy rain, and I have 
seen the same thing many times since. Yet there seems considerable 
probability that Boyer was right in part, and that the liquor found in 
