MORPHOLOGY 



53 



A particularly favourable object for the study of protoplasm in circulation is 

 afforded by the staminal hairs of Tradenamtia virginica. In each cell (Fig. 53) 

 small, fine currents of protoplasm flow in different directions in the peripheral 

 cytoplasmic layer, as well as in the cytoplasmic threads, which penetrate the sap 

 cavity. These cytoplasmic threads gradually change their form and structure, and 

 thus alter the position of the cell nucleus. The layers of hyaloplasm separating 

 the granular plasm from the cell walls and the internal sap cavities do not, in all 

 cases, take part in any of these circulatory movements. 



When the protoplasm is in rotation, the cell nucleus and chromatophores are 

 usually carried along by the current, yet there may be an outer layer of granular 

 plasm which remains motionless and retains the chromatophores. This is the case 

 with the Stoneworts (Characcae), whose long internodal cells, especially in the 

 genus Xitella, afford good examples of well-marked rotation. 



1 



Active cytoplasm is a viscous substance. Deprived of its com- 

 ponent water it becomes hard and tenacious, and, 

 without losing its vitality, it ceases to perform any 

 of its vital functions until again awakened into 

 activity by a fresh supply of water. In case of a 

 scarcity of water the jjlas'modia of the Myxomy- 

 cetes may form sclerotta, that is, masses of rest- 

 ing protoplasm of an almost wax-like consistency. 

 Months and indeed sometimes years afterwards, it 

 is possible from such sclerotia, if water be properly 

 supplied, to again produce motile plasmodia. Simi- 

 larly, in seeds kept for a long time, the proto- 

 plasm consolidates into a hard mass, which may 

 be easily cut with a knife, while the nuclei will 

 be found to have shrunk and lost their original 

 shape. Nevertheless the protoplasts, after ab- 

 sorbing water, may return again to a condition of 

 activity. 



Protoplasm is not a simple substance chemically ; 

 it consists rather of different components, which 

 are subject to continual change and in a state 

 of mutual reaction. Treated as a uniform mass, 

 protoplasm always gives a proteid reaction ; when 

 incinerated, fumes of ammonia are given off. 



a 



Fig. 53. — Cell from a 

 staminal hair of Tra- 

 dcsmntia virgiaico, 

 showing nucleus sus- 

 pended by protoplas- 

 mic strands, (x 240.) 



Active protoplasm generally gives an alkaline, and, 

 under certain conditions, a neutral reaction, but never 



an acid one. The protoplasm of the higher plants coagulates at a tempera- 

 ture not much over 50° C, in the Sehizophytes, however, usually not below 

 75° C. In a state of inactivity, as in spores and seeds, it can endure a still 

 higher temperature without coagulating ; when coagulation has once taken 

 place, death ensues. The spores of many Bacteria can withstand a tempera- 

 ture as high as 105° C. Treated with alcohol or ether, or with acids of definite 

 concentrations, with bichromates of the alkali metals, or with corrosive sub- 

 limate, protoplasm quickly coagulates, while at the same time insoluble proteid 



