THE COMMON TEASEL AS A CARNIVOROUS PLANT 
41 
of a Sarracenia (P sp.) growing in New Jersey (see Howard, Dyar, 
and Knab, Mosquitos N. and Centr. America, iii. (1), pp. 97-101 : 
1915). Again, J. C. H. de Meijere has described seven species of 
Hiptera which, in Java, make exactly the same use of the pitchers 
of Nepenthes (see Ann. Jard. Bot. Buitzenzorg, 2nd ser. Supp. iii. 
pp. 917-940: Leyden, 1910). Hepburn and Jones have shown that 
the larvae of Scircophaya sarracenice (and probably those of the other 
two species named above) are able to live in the digestive fluid in the 
pitchers of Sarracenia because their bodies contain certain “ anti- 
proteases,” or digestion-resisting compounds (see Contrib. Bot. 
Laboratories Univ. Pennsylv. iv. pp. 460—4(33 : 1919). It is, perhaps, 
because these substances are absent from the bodies of the larvae of 
our English mosquitoes that these latter cannot (or, apparently, do 
not) live in the putrescent liquor in the cups of the Teasel. 
It is clear from what has been said that insects and many other 
small creatures are captured and drowned, at all times and in large 
numbers, in the water-cups of the Teasel. It is necessary, therefore, 
to enquire how this is effected and why. 
That the formation of the cups is well adapted to retain any small 
creatures which may enter them is obvious. First, the sides of the 
cups are sloped very steeply, the leaves forming them being set at an 
angle of about 30 degrees with the stem and about 60 degrees with 
the surface of the ground, while the wing which connects the bases 
of the leaves is sloped at an even sharper angle with the stem. 
Secondly, the surface of the stem and the interior surface of the cups 
are both extremely smooth and glossy, rendering it likely that any 
small creatures which may have been induced, by whatever means, to 
enter or approach the cups will slip down into the liquor in their 
bottoms and be drowned therein. As Sir Francis Darwin has 
remarked (pp. cit. 270): “The plant is well adapted for catching 
and drowning insects. . . . The cups undoubtedly form most efficient 
traps. ... I have seen a beetle struggling to get out and observed 
his tarsi slipping, over and over again, on the smooth stalk.” 
There is, however, nothing in the foregoing, and apparently 
nothing in connexion with the structure of the plant or its water- 
cups, to suggest, at first sight, why so many small creatures should 
enter the cups at all (unless, perhaps, to drink in time of exceptional 
drought); still less why they should get drowned therein so 
frequently. 
Both Boyer and Barthelemy took the view that the many small 
creatures found in the cups had all “fallen” in ( tomhent ). Kerner 
(/. c .) clearly shares that view. Yet the presence in the cups of 
numerous dead insects is (as has been shown) almost invariable. 
This cannot be due solely to accidental causes ; for it is impossible to 
suppose that the presence of so many dead creatures in such com¬ 
paratively minute areas of water can be due merely to wind-transport, 
rain-wash, accidental falls, or other such casual causes. There must 
surely be something which definitely attracts the creatures in 
question: otherwise, they would not be found in the water so 
invariably and in such numbers. 
Subject to careful chemical investigation, I can only explain the 
