Development f and Structure of the Vegetable Cell. 481 



during the earlier development of the secondary and subsequent 

 generations of the true pollen-cells. 



Of these I select the Althaa rosea as the best-known example : 

 its June buds, in rapid evolution, before the opening of the first 

 flowers, furnished me with my best material. The later flower- 

 buds, which vegetate more languidly, and perhaps scarcely 

 attain their complete development, are not suited for this inves- 

 tigation. The buds, when taken from the plant, must be ex- 

 amined immediately. 



The figures given in Plate V. may be appealed to in illustra- 

 tion, and save description. Figure 13 exhibits the eight large 

 thick-walled cells which occupy the median line of each of the 

 two compartments of the young anther of Althaa rosea. Each 

 of these large cells was invested with a double membrane, and 

 its cavity was filled with a granular mucilaginous fluid, in which 

 a nucleus containing one nuclear corpuscle could be detected. 

 (The two uppermost cells were emptied in making the preparation.) 

 Around the central nucleus, at a certain stage of development, 

 were four, or more rarely two, spherical clear spaces, of larger 

 or smaller size (13 a"). Now and then, also, in the interior of 

 these clear spaces, a central vesicle, indicative of their cellular 

 nature, was visible. 



When these endogenous cells do not yet shimmer through the 

 turbid granular plasma, they may not unfrequently be recog- 

 nized during the gradual action of water upon their mother 

 cells, especially when the latter are still enclosed (as in fig. 13) 

 in their common mother cell. This action of the water consists 

 not so much in a solution of the plasma as in an extension of 

 the membranes of the enclosed cells, by which means the con- 

 trast between their cavities filled with turbid mucilaginous fluid 

 and the surrounding granular plasma is rendered more striking. 



After this cambial cell-mass has been acted upon by the 

 water for some time, and the cavities within the mother cells 

 have thereby acquired increasing clearness of outline, they sud- 

 denly vanish, usually all four at the same instant, and rarely 

 one later than the rest and after acquiring still more distinct- 

 ness. To all appearance, the tension of the cell-membranes by 

 endosmosis attains its maximum, and then the cells collapse 

 and disappear, their contents intermingling with those of the 

 mother cell. 



That these clear spaces, which are seen to enlarge by imbibi- 

 tion of water under the eye of the observer, do actually possess 

 membranous walls, and constitute actual cells capable of endos- 

 mosis, is the less doubtful, as a cell-nucleus is sometimes ob- 

 served in them. And that they may be four-cell-nuclei inca- 

 pable of alteration in the normal course of growth, is disproved 



