270 Professor Henslow's Examination 



The veins (c), (d), &c. are in all cases composed of bundles of 

 tracheae, which in the larger veins (c) are very numerous. I have 

 counted sometimes between thirty and fifty combined in the con- 

 struction of a single vein (c), a fact which would not be suspected 

 upon a casual observation, but which becomes evident by digesting 

 the style in nitric acid, when these elementary parts are easily 

 separated. Their terminations are in the form of elongated cones, 

 and they all end together, a short distance below the stigma. (See 

 Plate xvin. Fig. 3.) The other elementary parts of all these veins 

 are certain extremely delicate tubes which invest the central bundle 

 of trachea?, and give it the appearance of being surrounded by 

 a mucous or glutinous substance, but which under the highest 

 powers of the microscope may be separated into these tubular 

 vessels, whether subdivided or not by transverse diaphragms, I 

 was unable to satisfy myself. This very delicate tissue has the 

 same general appearance as the stigmatic tissue, which in these 

 plants descends down the centre of the style, to the summit of 

 the placenta. Where this latter tissue terminates in the stigma, it is 

 indeed evidently composed of distinct cells, easily separable from 

 each other by nitric acid, Plate xvm. Fig. 3. (<?). Lower down 

 however the cells are more elongated (?), and lower still, where 

 this tissue meets the placenta, I could neither detect any 

 transverse diaphragms in it, nor even detach its cells (if they 

 were such) from each other at their extremities by the action 

 of nitric acid, though they were easily separated longitudinally 

 into long filamentous strings. In this part of its course therefore 

 the stigmatic tissue appears rather to be tubular than cellular in 

 its structure. After this tissue has become divided into two bands, 

 penetrating on either side through the dissepiment into the two 

 cells, it seemed to me, upon a most careful examination, to coat 



