136 



PHARMACEUTICAL BACTERIOLOGY 



becoming extruded. In the course of four or five weeks the vacuoles 

 gradually became smaller and smaller and finally disappeared alto- 

 gether. In time many of the sphaerocytes developed plasmic threads 

 which extended from side to side across the cell. In many cases the nucleus 

 divided into from several to perhaps as many as thirty and more, second- 

 ary nuclei; these secondary nuclei being invariably smaller than the 

 mother nucleus. 



Fig. 49. — Sphaerocytes of the pulp cells of the immature squash. A, pulp cell; 

 a/nucleus with irregular branching nucleolus; b, sphaerocytes in various stagef- of de- 

 velopment; c, starch granules; d, plasmic granules, some of which are capable of very 

 active movement. B, nucleus enlarged, showing irregular and branching nucleolus and 

 outer irregular branching particles. C, a sphaerocyte more highly magnified, showing 

 outer irregular branching particles resembling those of the nucleus. D, illustrating 

 motion of two plasmic granules (a, b), which meet at (c), where they come to rest. E, 

 illustrating a more complex form of motion of plasmic granules. 



Fig. 49, X 1000; D and E represent the directions and distances traveled by four 

 different plasmic granules within a period of about S seconds, going at a speed of from 

 3 to 8 microns per second. At that rate the plasmic granule travels from 0.18 to 0.48 

 millimeters in one minute. 



One of the functions of the sphaerocytes is to continue the life of the 

 plant part, as fruit or seed, after the plant part has become separated from 

 the mother plant. That is, the plasmic activities are centered in the 

 sphaerocytes, rather than in the cell plasm or in the nucleus of the mother 

 cell. A second and perhaps equally important function is the warding off 

 of infections. The nucleo-sphaerocytes in particular show a high resist- 

 ance to the successful invasion by the various organisms of infection, as 

 rotting bacteria, yeasts and molds. Hanging drop cultures rich in sphae- 

 rocytes remained free from infection even with rather careless manipula- 



