208 FRANCIS DARWIN. 



mention another plienoineiion which I do not understand, bnt 

 which is the almost universal result of treatment with 4- or |; % 

 solution of carbonate of ammonia. It consists in the appear- 

 ance of numerous brig^ht, hi2,ldy refracting drops of resin in the 

 epidermic cells^ which gradually run together and form large 

 spheres. They are very easily soluble in methylated spirit, and, 

 no doubt, consist of the same resinous matter secreted by the 

 glands. A similar effect was extremely well marked, and re- 

 peatedly seen in preparations mounted in 75 % solution 

 of acetate of strychnia. No other substances seem to have the 

 same power, and the phenomenon must remain unexplained. 

 At first sight the protrusion of fih\ments, and the changes which 

 occur in them, appear to be isolated phenomena unrelated to 

 any known physiological ])rocess, except in a certain way with 

 secretion. I beheve, however, that some relationship must 

 exist between the protrusion and amoeboid movements of the 

 tilaments, and the process of aggregation as it occurs, for 

 example, in the tentacles of Drosera. The physiological meaning 

 of the latter phenomenon is at present unknown ; we know, at 

 least, that variously shaped protoplasmic (?) masses make their 

 appearance and undergo incessant movement. If these masses 

 were to traverse the external cell-wall, and protrude into the 

 surrounding medium, they would closely resemble the filaments 

 of the teasel. The following are the points of resemblance be- 

 tween the protruded filaments of the teasel and the aggregated 

 masses of Drosera : 



(1.) Both consist of homogeneous, highly refracting masses 

 of protoplasm, imbued with a large quantity of metaplasm ; the 

 latter being fatty (?) in Drosera, resinous in Dipsacus. 



Both are connected with glandular organs, which not only 

 secrete certain substances, but also absorb nitrogenous materials. 



The comprehension of the relations between the processes of 

 protrusion and aggregation is rendered more difficult by the 

 fact that true aggregation takes place within the trichomes of 

 the teasel. 



The production of filaments is not an unknown occurrence in 

 the ordinary protoplasmic contents of cells. Max Schultzei 

 describes in the stinging hairs of the nettle the appearance of a 

 certain number of threads i)rojecting from the parietal protoplasm 

 into the cell-sap ; their free extremities are swollen or clubbed, 

 and they are in a state of trembling movement. These appearances 

 are only seen when the electric current to which the hair is 

 subjected is nearly strong enough to kill the protoplasm. 



I have occasionally seen these internal filaments, for instance in 

 a »land which bore also an ordinary external filament. By careful 



' Quoted by Sachs, ' Pliysiologie Vegetale' (French translation), p. SO. 



