ON PROTRUSION OF PROTOPLASMIC FILAMENTS. 269 



focussing with No. 9 Hartnack I made certain that there was a 

 filament actually inside the gland ; and it was proved not to be 

 outside by irrigating with methylated spirit, by which means 

 the external filament was made to contract while the internal 

 one was unaffected. The same appearance of trembling clubbed 

 filaments was seen in one of the large conical hairs on the seed- 

 ling teasel-leaf. Three of such filaments are marked by crosses 

 in fig. 12 ; the largest of the three waved to and fro, and re- 

 minded me closely of one of the ordinary external filaments. 



Relation between the general structure of the Teasel and the 

 protrusion of Ji laments. — The conclusion to which the study of 

 the filaments and the glands seems to lead is, that they are both 

 capable of absorbing nitrogenous fluids. It will be well to 

 consider whether or not the general structure of the teasel is in 

 any way co-ordinated with this power. 



In the first place, it is quite certain that the plant is well 

 adapted for catching and drowning insects. ^ 



The connate leaves form cups holding from 12 to 100 c.c. of 

 fluid ; the leaves are smooth" (although those of the seedlings 

 are rough, with large prickly hairs) and are inclined so as to form 

 a large angle with the horizon and a small one with the vertical; 

 they form, therefore, two steep and slippery slides, leading to a 

 pool of water. The stalk of the plant is covered with sharp 

 prickles, but these cease where the stalk dips into the water iji 

 the cup. If it were not for the loss of the prickles at this 

 point, a ladder of escape would be provided for the drowning 

 victims. I have seen a beetle struggling to get out, and 

 observed his tarsi slipping over and over again on the smooth 

 stalk. The cups undoubtedly form a most efficient trap. In 

 some wild teasels the following insects were found : — In one cup six 

 large malacoderm beetles, from half to three quarters of an inch 

 in length, one fair-sized caterpillar, and two flies; in another, 

 seven of the same beetles, one earwig, a bluebottle fly, besides 



' Prof. Kerner believes that the " cups " of the teasel are a protection 

 to the flower against the attacks of ants and other wingless insects who 

 might steal the nectar without benefiting the species. In his recent 

 memoir, " Die Scliutz-Mittel der Blumen gegen unberufene Gaste," in the 

 ' Proceedings of the K. K. Zoolog. Botan. Gesellschaft, Vienna,' 1876, he 

 supports, with strong arguments, the theory that many flowers are thus 

 protected. He would, however, be the first to admit that a given structui-e 

 may have developed through serving more tlian one useful purpose. It 

 is curious that in the last century Erasmus Darwin should have remarked 

 on the protective function of the " bason " formed by connate leaves of 

 the teasel. He even alludes to nectar as one of the treasures to be 

 guarded in this kind of way, although he was not, of course, aware of 

 the true relations existing between flowers and insects. (See ' Loves of 

 the Plants,' Note 6.) 



^ The glands do not make the leaves appreciably rough. 



