1877.] 



Protoplasmic Filaments from the Teasel. 



7 



plasm — that, for instance, the oil in a fat-cell is the result of the dis- 

 integration of a plastid or individualized mass of protoplasm formed in 

 the cell by endogenous cell-formation. 



The protrusion of protoplasmic filaments from the glands of the teasel 

 appears to bear an obscure relationship to the phenomena of " aggrega- 

 tion " in Drosera and several other plants. In both processes we have 

 homogeneous highly refracting protoplasmic masses, which undergo 

 amoeboid movements, and are in some unknown way connected with the 

 absorption of nitrogenous matter. In Drosera the protoplasmic masses 

 remain within certain cells ; in Dipsacus they are protruded through the 

 cell-wall. 



"When we begin to inquire as to the function of the filaments, the 

 answer seems at first to be sufficiently plain ; but this is very far from 

 being the case. The connate leaves of the teasel form cup-like cavities, 

 which become full of rain and dew and in which many drowned 

 insects accumulate. The glands at the base of the leaves are thus 

 exposed to a highly nitrogenous fluid. And since such fluids are known 

 to produce a remarkable effect on the filaments exposed to them, it seems 

 probable that the filaments are in some way connected with the assimi- 

 lation of food material. It seems probable that, either with or without 

 the assistance of their filaments, the glands do absorb some nitrogenous 

 matter ; for changes of their cell-contents occasionally occur which can 

 only thus be interpreted. But on account of the rarity and uncer- 

 tainty of these aggregation changes within the glands, but little weight 

 must be allowed to the phenomena as a proof of the absorbing capacity 

 of the glands. Some other points in the structure of the plant 

 render it almost certain that the connate leaves are specially adapted to 

 serve some useful purpose. Kerner is probably right in believing that 

 the " cups " of the teasel are of use to the plant in keeping off nectar- 

 stealing ants and other wingless insects ; but unless this is their only 

 function, it seems probable that the connate leaves have been to a certain 

 extent adapted for the capture of insects whose decaying remains are 

 absorbed by the plant. The leaves are smooth and steeply inclined, and 

 form a pair of treacherous slides leading down to a pool of water. 



It is worthy of note that the leaves of the first year's growth, which 

 do not form cups, are not smooth, but bristle with long sharp hairs ; 

 moreover in Dipsacus pilosus the leaves (of the second year's growth) are 

 not sufficiently connate to form cups, and they also are rough with hairs. 

 These facts seem to show that the smoothness of the second-year leaves 

 in D. sylvestris is a specially acquired quality. Another special point of 

 structure in D. sylvestris may be. noted. The stems are everywhere 

 armed with sharp, prickles, except where they are covered by the water 

 in the " cups ; " and here they are quite smooth, so that no ladder 

 of escape is afforded to the drowning victims. Even if we grant 

 from the above considerations that the filaments protruded from the 



