iOl- Investigation of the Structure 



that I myself had proposed to others, I determined to com- 

 mence several experiments ; and the detail of two of these, 

 with their results, will form the subject of the present com- 

 munication. 



A few fine seeds of the balsam, which had been ripened at 

 Madras in 1830, were sown early in March last, and kept in 

 a pine-stove during the course of their growth. Two of them, 

 about 2 in. in the clear stem, were selected : one of these 

 was pale, the other was tinged with red ; they were planted 

 in separate small pots, in light soil, composed of heath mould 

 and decayed leaves chiefly. Tlie plant with the pale stem was 

 watered almost entirely with a strong solution of logwood ; 

 but it received, two or three times, a slight refreshment of 

 pure water, when, by oversight, and the great heat of the 

 house (occasionally above 100°), the soil had become quite 

 dry. During three weeks that I carried on this process, the 

 plant, although it lived and stood erect as long as the soil was 

 in a moist state, made little or no progress in growth. I men- 

 tion this fact, because it shows that watery coloured infusions, 

 though highly impregnated with carbonaceous matter (and 

 therefore, as might be supposed, abounding with vegetable 

 aliment), furnish, in reality, no appropriate food to some 

 plants; to the balsam in particular. 



The other plant, that with the red stem, was supplied with 

 pure water only, for about a fortnight; and it grew much 

 better than the one that was treated with the infusion. It 

 now was taken up, its root cleansed from the soil, and placed 

 in a glass vessel, containing a deeply coloured infusion of log- 

 wood. Both the plants were kept in the stove, and there 

 they remained for another week ; at the end of which they 

 were carefully investigated. 



1st, The plant with the white stem, the soil of which had 

 been watered with the infusion, was removed from the pot, 

 and its roots washed ; it was then supported by tweezers, so 

 as not to injure it, and its stem was examined by the micro- 

 scope, under every situation, with respect to light, that could 

 be commanded. Not a particle of colouring matter could be 

 discerned under the cuticle (epidermis), and even when a 

 portion of that exterior integument was removed, there was 

 not the least discoverable appearance of colour among the 

 exposed cells. A small strip was next cut with a lancet along 

 the stem, so as to discover and detach some of the longitudinal 

 vessels. I mean those which were formerly believed to be 

 the tubular sap-conduits, whether, in their texture and con- 

 dition, they be spiral, annular, reticulated, or punctuated ; and 

 which corresponded with the tracheae, small and mixetl tubes 



