18 HOFFMANN ON THE CIRCULATION 



occuri'ed. A cross section at this point presents the following 

 appearance. At the outside a cortical layer, without vessels, 

 the starchy parenchyma of which is separated from the large 

 central parenchyma of the stem by a kind of liber-layer : the 

 central parenchyma, forming the great body of the stem, con- 

 tains scattered vessels divided into two sets, a central and a 

 peripherical, between which lies a ring of parenchyma free from 

 vessels. The cells which became blue lie in the vicinity of the 

 vascular bundles ; the gummy cortical layer was devoid of them. 

 It is worthy of notice that both the boundary between the liber 

 and parenchyma, properly the outermost layer of the central 

 cellular mass, and the immediate environs of the vessels scat- 

 tered in the central mass, emitted a small quantity of a tenacious 

 white sap, in which were suspended a few starch-granules and 

 an extraordinary quantity of minute raphides. No ferrocyanide 

 could be detected in the cortical layer even after the space of a 

 month. 



Chlorophytum StembergianmHy Steudl. (Liliaceae). — In this 

 plant, which appears to derive the greatest part of the requisite 

 moisture from the atmosphere, it is difficult to diffuse a quantity 

 of the salt sufficient for the reaction in the ordinary way. The 

 slender filiform stem to which the tuft of leaves with their aerial 

 rhizomes and roots is attached, died in a few weeks, in conse- 

 quence of the watering, without much of the liquid having been 

 absorbed. In this case the cells of the bases of the leaves, as 

 also the aerial roots and the rhizomatous tubers, exhibited a 

 weak blue colour when cut surfaces were wetted with sulphate 

 of peroxide of iron. A clearer view may be obtained in a differ- 

 ent way. The aerial roots readily absorb fluids, for instance 

 water, when they are dipped into it ; moreover, sulphate of iron 

 was decomposed, the oxide fell as a yellow powder to the bot- 

 tom of the glass, while the w^ater penetrated into the plant; on 

 the other hand, a large aerial root which was already buried 

 in the earth and had taken root there, readily absorbed so much 

 ferrocyanide that this could be easily detected in longitudinal 

 and transverse sections several inches above the ground. The 

 central layer containing the dotted vascular bundles was found 

 free from colour ; but all the rest of the tissue, composed of 



