248 FRANCIS DABWIN. 



formed by the distal end of the filament becoming attached to the 

 gland, but I believe that they arise as loops, or that two filaments 

 unite and form a loop immediately after emerging from the 

 gland. Variously beaded forms are shown in fig. 9, and a crowd 

 of irregularly shaped masses in fig. 7. 



The filaments are with the very rarest exceptions attached to 

 the summit of the gland ; and when the actual place of attach- 

 ment can be made out, it is found to be at the point where the 

 radiating cells meet in the centre of the dome-like surface of the 

 gland, or at least on the junction line between at least two cells. 

 The substance of which the filaments are composed is trans- 

 lucent, highly refracting, and quite free from granules. The 

 filaments are in constant tremulous Brownian movement, showing 

 that they are of a gelatinous consistence. I hope to prove that 

 they consist in part at least of protoplasm, but I have not suc- 

 ceeded in showing the presence of albuminoids by any of the 

 usual micro-chemical tests. Neither the rose-red colour with 

 syrup and sulphuric acid, nor the xanthoprotein test with nitric 

 acid and ammonia succeeded properly, though a distinct faint 

 tinge was produced by the latter means. The filaments, how- 

 ever, assume a bright yellow colour with iodine, but I presume 

 that no great weight ought to be attached to this reaction. The 

 filaments are not stained by ordinary colouring fluids, such as 

 logwood, anilin, &c. It will be shown that the substance of 

 which they are composed consists in large measure of a resinous 

 substance mingled in some way with the protoplasm, and I pre- 

 sume that it is this circumstance which interferes with the above 

 reactions. 



Protrusion of the motile filaments from inside the glandular 

 trichomes. — I have hitherto spoken of the filaments as merely 

 attached to the surface of the glands, but they are in fact pro- 

 truded from the inside. There can be no doubt of this, for 

 glands may be observed whose dome-like summits are quite 

 naked and bare, but which may be seen after a few moments to 

 be surmounted by a minute projection which grows up into a 

 normal filament by visible increments in length. I cannot posi- 

 tively state by what means the filaments traverse the external 

 cell-walls. It might be supposed that apertures would be found 

 to allow of their transmission. By stripping ofl" the epidermis 

 a bird's-eye view of the summits of the trichomes is obtained, 

 and if any apertures exist they would be probably visible in 

 this way, but no such appearance can be seen. But the tops of 

 the trichomes ought to be cut off by sections parallel to the sur- 

 face of the leaf, to decide the point with certainty. It is ex- 

 tremely unlikely that apertures should exist, and the protrusion 

 of the filaments can be explained without assuming their exist- 



