OF SAP IN PLANTS. 9 



reagent to the petals (stripped of some of the epidermis by 

 shaving with a razor), showed the error of the first conjecture. 

 Into the sepals of the specimen, on the contrary, the sap 

 ascended within a few days ; the same occurred in some half-ripe 

 fruits which existed upon other specimens. The following is a 

 detailed account of the anatomical conditions. 



The bulb does not consist of separate scales, but forms a kind 

 of tuber which is chiefly composed of a perfectly homogeneous 

 mass abounding in starch ; the outer coat is a reticulated shell 

 composed of two membranes : a thick bundle of vascular cords 

 runs up the centre. The starchy parenchyma does not react 

 blue, neither does the vascular mass in the centre, in the separate 

 vessels of which air may be detected by the microscope ; but a 

 very dark blue colour was seen in innumerable closely-crowded 

 little points in the cortical layer or shell. And the presence of 

 the ferrocyanide in the cortical substance did not depend upon 

 a penetration from without during the watering of the specimen, 

 and thus upon a penetration into the interior by an unusual 

 path ; for the outer coating of all showed 110 reaction whatever 

 with the salt of iron, while the blue colour was scarcely per- 

 ceptible inside the finest of the root-fibrils. The shell of the 

 bulb contains no air-vessels or spiral structures, but is traversed 

 in all directions by numerous anastomosing liber bundles, 

 which are sharply defined against the looser cellular substance 

 surrounding them, and give the shell the open reticulated aspect 

 already mentioned. These liber bundles exhibited no reaction ; 

 in the transverse section they look like large yellowish circles, 

 which are clearly contrasted against the surrounding blue cel- 

 lular spots. The cells lying between these bundles are of two 

 kinds ; those lying next them are narrower, more slender and 

 more elongated than the rest, which exhibit a rounded four- or 

 five-angled form ; it was these elongated cells which were coloured 

 blue by the application of the salt of iron, while the remaining 

 cells remained for the most part altogether uncoloured. The 

 blue-coloured cells frequently lie several one behind the other, 

 so that it is easy to trace the straight line in which the sap ad- 

 vances, without deviating to the side ; in other cases, especially 

 in the rest of the parenchyma, they frequently lie isolated, 

 whence it appears to follow, that the motion of the sap is not 



