292 Mr Carry, On the Development of [Nov. 27, 



That vertical wall of each of the limiting tapetal cells which is 

 adjacent to the special-mother-cells now undergoes, at least in part 

 conversion into cutin, and in so doing increases considerably in vol- 

 ume; the chemical change is likewise accompanied by a change in 

 color from colorless to pale yellow. This change is followed suc- 

 cessively by a like conversion of all the walls surrounding the 

 special-mother-cells which assume the same tint. On treating 

 these walls with concentrated sulphuric acid a pale ruby-red color 

 is produced in all alike. 



In this manner the pollinium is produced, and it can at this 

 period be extracted from the anther-loculus in the form of a 

 single definite compact solid coherent mass of considerable size, 

 with a deep golden-yellow color and a waxy look externally. 

 Its surface, which is perfectly smooth, presents the appearance of 

 being divided in a reticulate manner into areolae or hexagonal 

 meshes, the apparent bulging of each areola being caused by the 

 shape of the underlying cell filled with protoplasm. 



Each pollinium contains all the adherent or firmly united 

 special-pollen-mother- cells produced in one anther-loculus or 

 pollen-sac. In transverse section it exhibits a cellular appear- 

 ance and structure, consisting of three series or rows of cells 1 , 

 parallel to its sides, the middle series being more or less inter- 

 rupted. These cells are enclosed by thick, pale-yellow-colored, 

 semi-transparent cell-walls, the cell-walls of those belonging to 

 the two outer rows being continuous at certain points with, and 

 surrounded by, a deep golden-yellow, pellucid, cuticularized mem- 

 brane, which has a resistant horny texture, cuts with great ease, 

 and is derived from the change of those portions of the surfaces 

 of the tapetal cell-membranes immediately adjacent to the 

 special-mother-cells. This membrane, forming an unbroken 

 sheet, encloses and envelops completely every part of the entire, 

 compact, solid, concrete mass of coherent special-mother-cells 

 filling the anther-loculus, thus forming a general coat of consi- 

 derable thickness. Brongniart 2 , and Schleiden (Principles of 

 Scientific Botany, Ed. III. 1849, p. 356) both believed that this 

 yellow investing membrane, which I have shewn to be formed 

 from the tapetum was itself really of a cellular nature, i.e. com- 

 posed of cells ; for the former observer tells us that the arcolate 

 appearance is due " not to the underlying cellular mass but to the 

 cells themselves, which constitute the membrane and which are 

 disposed after the fashion of epidermal cells;" while the latter 

 regards it as formed "of the outermost layer of the special-mother- 



1 In the oblique planes of the original prismatic mother-cells each row consists 

 of four cells and not three. The relation of the descriptions framed from the two 

 points of view, viz. perpendicular and oblique, is however easily obvious. 



2 loc. cit. p. 267. 



