24 Practical Plant Biology. 



extending from the cell-wall inwards and occupying nearly all the 

 space encircled by the wall. This is the protoplasm of the cell. 

 There are often one or more circular patches in the section, of 

 less bright substance, surrounded by the protoplasm : these are 

 vacuoles. Very often, when examined in bright daylight, the 

 protoplasm appears pale bluish, while in contrast to it the vacuoles 

 seem duller and tinged with pink. By frequent readjustments of 

 the mirror, the focus of the condenser and the aperture of the 



FIG. 5. Saccharotnyces cerevisece. a, a single plant, x 2500 ; b, c t d, 

 budding plants; e,f, formation of spores; g, h, germination of spores. 

 (From Evans: An Intermediate Textbook of Botany. After Reess.) 



diaphragm you will arrive at clearly distinguishing these structures, 

 and also during these manipulations you will discover, most 

 probably, various very minute specks in the protoplasm and even 

 in the vacuole. Where specks are seen in the vacuole they 

 usually show the peculiar dancing motion which they, in common 

 with all very minute bodies suspended in fluids, exhibit. This 

 motion is considered to be due to the impacts of the molecules 

 of the medium on the particles and becomes apparent when the 



