Chap. XVI. SECRETION, ABSOEPTION, DIGESTION. 387 



much secretion; they were then placed on damp sand under 

 conditions known to be favourable for germination. Three 

 never germinated, and this was a far larger proportion of deaths 

 than occurred with seeds of the same lot, which had not been 

 subjected to the secretion, but were otherwise treated in the 

 same manner. Of the eleven seedlings raised, three had the 

 edges of their cotyledons slightly browned, as if scorched ; and 

 the cotyledons of one grew into a curious indented shape. Two 

 mustard seeds germinated; but their cotyledons were marked 

 with brown patches and their radicles deformed. Of tv/o radish 

 seeds, neither germinated ; whereas of many seeds of the same 

 lot not subjected to the secretion, all, excepticg one, germinated. 

 Of the two Eumex seeds, one died and the other germinated ; 

 but its radicle was brown and soon withered. Both seeds of the 

 Avena germinated, one grew well, the other had its radicle brown 

 and withered. Of six seeds of the Erica none germinated, and 

 when cut open after having been left for five months on damp 

 sand, one alone seemed alive. Twenty-two seeds of various 

 kinds were found adhering to the leaves of plants growing in a 

 state of nature ; and of these, though kept for five months on 

 damp sand, none germinated, some being then evidently dead. 



The Effects of Ohjecis not containing Soluble Nitrorjenous Matter. 



(16) It has already been shown that bits of glass, placed on 

 leaves, excite little or no secretion. The small amount which 

 lay beneath the fragments was tested and found not acid. A 

 bit of wood excited no secretion ; nor did the several kinds of 

 seeds of which the coats are not permeable to the secretion, and 

 which, therefore, acted like inorganic bodies. Cubes of fat, left 

 for two days on a leaf, produced no effect. 



(17) A particle of white sugar, j^laced on a leaf, formed in 

 1 hr. 10 m. a large drop of fluid, which in the course of 2 

 additional hours ran down into the naturally inflected margin. 

 This fluid was not in the least acid, and began to dry up, or 

 more probably was absorbed, in 5 hrs. 30 m. The experiment 

 was repeated; particles being placed on a leaf, and others of 

 the same size on a slip of glass in a moistened state ; both being 

 covered by a bell-glass. This was done to see whether the 

 increased amount of fluid on the leaves could be due to mere 

 ieliquescence ; but this was proved not to be the case. The 

 particle on the leaf caused so much secretion that in the course 

 of 4 hrs. it ran down across two-thirds of the leaf. After 8 hrs. 

 the leaf, which was concave, was actually filled with very viscid 



