162 G. L. Kite 



into water, not only do not go into the sol state but remain too rigid 

 to show surface tension effects. Pieces of broken glass needles stick 

 firmly to the nuclear gel when imbedded in it. The image of the 

 nucleus is false in important details. The denser areas, when in the 

 focal plane, appear as grayish or slightly opalescent . granules and 

 threads and when above or below the focal plane as dark spots 

 and lines. Besides, if the intensity of the illumination be increased 

 the network appears much finer. Very small dense masses of gel 

 could be partly freed from the remaining nuclear substance. It 

 seems proper to term such structures granules. On the other hand, 

 the dense masses that produce the appearance of a network in the 

 image are not actual threads that are sharply separated from the 

 surrounding gel but irregularly shaped dense areas that grade into 

 the immediately contiguous diluter gel. The light spots that change 

 their position at different focal planes seem to be due chiefly to 

 two factors, viz., a relatively low absorptive power of the gel 

 occupying the interstices of the network and diffraction by the edges 

 of the denser areas. 



It seems certain that the vacuolar fluid of Spirogyra contains 

 protein and must be considered a hydrosol. Much evidence has 

 been adduced in support of this statement. A number of injections 

 of Millon's fluid into the vacuole were made with positive results. 

 Extremely small solid particles appeared in the cell sap after the 

 injection of such precipitating agents for proteins, as saturated subli- 

 mate, 40 per cent formaldehyde, saturated picric acid and saturated 

 phosphotungstic acid containing 5 per cent sulphuric acid. 



The vacuolar fluid is cloudy. This is positive proof of the pres- 

 ence of ultramicroscopic particles which would ordinarily be con- 

 sidered protein even in the absence of a positive color test for protein. 



The cell sap of Chara seems to be richer in protein than that of 

 Spirogyra. This conclusion is based on the fact that a compara- 

 tively heavy precipitate results from the in tra vacuolar injection of 

 saturated sublimate or 40 per cent formaldehyde. Hence, it is proba- 

 ble that cell sap containing protein is very common in plants. 



Mucor, Saprolegnia, Hydrodictyon, Chara and the parenchymatous 

 cells of the leaves of Tradescantia have been dissected for comparison 

 with animal cells. In general, it may be stated that the cellulose 

 walls of plants are extremely cohesive and are cut and punctured 



