FORM OF THE PLANT-CELL. 37 



vesicles of carbonic acid gas. On the fourth day fermentation was very 

 active. At the bottom of the vessel, and on the surface of the fluid, yeast 

 had formed : but these yeasts consisted of single cells, or several attached 

 one to another. In the solitary cells could be observed the way in which 

 one cell was formed from another (Plate I. fig. 9. d, e, /). The ferment- 

 cells do not in this state permit of a distinction between the contents and 

 the membrane of the cell. In the midst of the cell there is a transparent 

 spot ; but whether hollow, or a solid nucleus, I could not decide. The re- 

 maining parts appeared entirely homogeneous, yellowish like a nitroge- 

 nous substance, sometimes mixed with small solitary granules (Plate I. 

 fig. 9. d, e,f). In a similar way, a solution of sugar with elder-flowers 

 was examined, and gave similar results. Other results were obtained in 

 the following way. Pure white protein (albumen), from the white of an 

 egg, was dried, and rubbed down with sugar, and left to ferment : the fluid 

 at first was perfectly clear. On the third day, the small portions of pro- 

 tein, which at the commencement exhibited a sharply angular aspect, 

 assumed partly a granular aspect, and some a more or less rounded form. 

 These globules showed an active molecular movement, and some appeared 

 strung together. On the fourth day there was seen between these granules 

 round or elongated cells, which were either solitary, or arranged together 

 in a line with a tendency to the formation of branched fibres. These cells 

 were not more than one-third of the diameter of ordinary ferment-cells 

 (Plate I. fig. 10. c, d). An active fermentation went on, and gas-bubbles 

 were given out from the protein-granules and the linear cells. Proper 

 ferment-cells did not make their appearance. Fluid albumen, mixed with 

 sugar and filtered, became thickened on the second day, and contained 

 little granules of albumen (coagulated?). The further phenomena were 

 similar to those exhibited by the preceding, except that there were deve- 

 loped a few true ferment- cells. Protein moistened with water displayed 

 the same appearances as when mixed with sugar and water ; ultimately 

 putrefaction came on, and the development of infusoria, but the vegetable 

 formation preceded. There appear to be two very different types of 

 ferment-cells, according as the fluid contains organic acids and essen- 

 tial oils or not. From the phenomena exhibited by the ferment-cells, 

 one might be inclined to regard them as similar to animal -cells, which 

 are formed through a cavity in the cytoblast, and which afford indica- 

 tions of the nucleoli in their highest development. But this analogy 

 is not tenable, and the above observations must be regarded as imperfect. 

 If we take fully developed ferment-cells, and treat them with ether, 

 alcohol, or caustic alkalies, there will be found in the fluid a number of 

 globular delicate cells, with thin but clearly distinguishable walls, which 

 contain a clear fluid, with here and there very small granules, which, 

 alone or in groups, are attached to the inner surface of the cell wall, and 

 (almost ?) always a large round flat body (a cytoblast ?). 



History and Criticism. Before the discovery and scientific use of the 

 microscope, of course there could be no accurate knowledge of the cells of 

 plants. 



Robert Hooke, an Englishman, was the first discoverer of the cellular 

 structure of plants. He used a microscope first brought to England by 

 Cornelius Drebbel in 1619. (Micrographia. London, 1667. Fol.) 



Marcello Malpighi, professor at Bologna, gave a more accurate account 

 of the structure of plants. He sent to the Royal Society of London his 

 great work, Anatome Plantarum, in the year 1 670, and which was pub- 

 lished in two volumes folio, at the expense of the Society, in 1675 and 



D 3 



