of Lathraa Squamaria, ^c. 415 



ments have, however, proved them to be filled with a glutinous 

 or mucilaginous fluid of much greater specific gravity than water ; 

 in which, though no larger than particles of the finest pollen, they 

 sink as freely as grains of sand. As they are not attached to the 

 sides of the cells, they may be easily separated by macerating 

 the leaf in water, and carefully removing the fecula with a 

 camel-hair pencil, when they will be found at the bottom like a 

 mass of impalpable particles of pounded glass. On evaporating 

 the water, and submitting them to a very considerable dry heat, 

 they still remain distended ; but on bruising them with the flat 

 side of a knife, they give out a fluid, which, though it becomes 

 stiff and fixed by heat, almost immediately regains its viscidity 

 by re-absorption from the atmosphere. From their extreme 

 minuteness this experiment can only be tried by collecting the 

 bladders in considerable quantity and examining the expressed 

 fluid under the microscope. In pure alcohol they generally 

 remain quiescent, not more than one in fifty, even of the small- 

 est, ranging about like particles of pollen similarly treated. 

 When held over a spirit-lamp, either in distilled water or in 

 alcohol, they burst simultaneously, but the shrivelled transpa- 

 rent skins still lie at the bottom of the fluid. The mucilage 

 diluted in alcohol retained its transparency ; in distilled water 

 it gave a red tinge to blue litmus paper, but did not aftect the 

 red litmus ; and on dropping into it a little diluted sulphuric 

 acid, a few milky or opal-coloured flakes were formed. No 

 sensible effect was produced by prussiate of potash or super- 

 acetate of lead. I tried in vain to crystallize it by evaporation ; 

 indeed, when removed out of a dry atmosphere, it almost imme- 

 diately resumed its viscidity. I am therefore disposed to con- 

 sider the contents of these bladders, a kind of liquid sugar, in- 

 capable of crystallization, from the little free acid it seems to 

 contain ; and that it is secreted from the aqueous juices in 

 VOL. XVI. 3 11 which 



