48 



BOTANY 



Fig. 49. — Copy of a part of 

 Hooke's illustration of 

 bottle-cork, which he en- 

 titled Schematism or tex- 

 ture of cork. 



hibiting by means of different objects the capabilities of his microscope ; 

 consequently, the Italian, Marcello Malpighi, and the Englishman, 

 Nehemiah Grew, whose works appeared almost 

 simultaneously a few years after Hooke's Micro- 

 graphia, have been regarded as the founders of 

 vegetable Histology. The living contents of the 

 cell, the real body or substance, was not re- 

 cognised in its full significance until the middle 

 of the present century. Only then was attention 

 turned more earnestly to this study, which has 

 since been so especially advanced by Meyen, 

 Schleiden, Hugo v. Mohl, Nageli, Ferdi- 

 nand Cohn, Pringsheim, and Max Schultze. 

 If an examination be made of a thin longi- 

 tudinal section of the apex of a stem of a phanero- 

 gamic plant, with a higher magnifying power 

 than that used in the previous investigation (Fig. 17) of the vegetative 

 cone, it will be seen that it consists of nearly rectangular cells (Fig. 50), 

 which are full of protoplasm and separated 

 from one another by delicate walls. In 

 each of the cells there will be clearly dis- 

 tinguishable a round body (k), which fills 

 up the greater part of the cell cavity. 

 This body is the cell nucleus. If sections, 

 made in different directions through the 

 vegetative cone, be compared with one 

 another, it will be seen that its component 

 cells are nearly cubical or tabular, while 

 the nuclei are more or less spherical or 

 disc-shaped. The finely granular substance 

 (cij) filling in the space between the nucleus 

 (k) and the cell wall (m) is the CELL plasm 

 or cytoplasm. Eecent investigations have 

 shown that two extremely small, colourless 

 bodies lie in the cytoplasm, near the nucleus. These are the 

 Centrospheres or attraction spheres (cs). In addition to these 

 there are to be found, about the nucleus, an indefinite number of 

 somewhat larger bodies, which are also colourless and highly refrac- 

 tive ; these are the pigment - bearers or CHROMATOPHORES (ch). 

 Nucleus, centrospheres, cytoplasm, and chromatophores, con- 

 stitute THE ELEMENTS OF THE LIVING BODY OF A TYPICAL VEGETABLE 

 CELL. To designate all these collectively, it is customary to use the 

 term Protoplasm, which is then to be understood as including all 

 the living constituents of a cell. 



Protoplasm does not show the same degree of internal differentia- 

 tion in all vegetable organisms. The protoplasm of the Fungi has no 



Fig. 50.— Embryonic cell from the 

 vegetative cone of a phanerogamic 

 plant, k, Nucleus ; 'kw, nuclear 

 membrane ; n, nucleolus ; c, cen- 

 trospheres ; cj/,~ cytoplasm ; eft, 

 chromatophores ; m, cell wall. 

 (Somewhat diagrammatic, x circa 

 1000.) 



