May 30, 1913] 



SCIENCE 



843 



right angles to the direction of the light. In 

 the main my observations on the physiology 

 of germination are in accord with those of 

 Farmer and Williams. In watch glasses, 

 placed on a laboratory table, the first division 

 is usually at right angles to the bottom of the 

 watch glass and at right angles to the direc- 

 tion of the light. Abnormalities in cleavage 

 and development as described by Kiister were 

 sometimes, but seldom, observed. The cell 

 away from the light is the rhizoidal cell, while 

 from the other cell the young thallus develops. 

 The subsequent cell divisions and growth of 

 the plantlets in watch glasses follow the de- 

 scriptions of Thuret and of Oltmanns and 

 need no special mention. In watch glasses 

 placed in larger dishes of sea-water, young 

 plants of about 25 cells were grown in the 

 laboratory. No attempt was made to rear the 

 plants beyond these young stages. 



In plants used to induce cell division by 

 artificial means great care was taken to pre- 

 vent contamination by sperms. The female 

 plants were carefully washed with fresh water 

 to kill any sperms which might adhere to 

 them. None of the eggs obtained from such 

 sterilized plants ever developed in the numer- 

 ous controls, which were run in connection 

 with the experiments, showing beyond a doubt 

 that the female plants treated were absolutely 

 sterile. 



Loeb has shown that, when unfertilized eggs 

 of the sea-urchin are placed for one and one- 

 half to two minutes in a mixture of 50 c.c. of 

 sea-water -|- 3 c.c. of 0.1 m acetic, butyric or 

 other fatty acid and then transferred to nor- 

 mal sea-water, a fertilization membrane is 

 formed. This method was applied to unfer- 

 tilized Fucus eggs. In experimenting with 

 the eggs those used at any one time were al- 

 ways divided into three lots. One lot was 

 used as a control, another was fertilized and 

 the third was treated with the solution. If a 

 single egg in the control formed a cell-wall, 

 which seldom happened, the three lots were 

 discarded. In ease the eggs were treated with 

 acetic or butyric acid, as above described, a 

 large number of them formed in about ten 



minutes a membrane or cell-wall which was 

 exactly similar to the one formed about nor- 

 mally fertilized eggs. By plasmolyzing the 

 eggs the membrane is readily seen. Eggs 

 not treated with a solution or not fertilized 

 undergo cytolysis and degenerate. In any 

 case many of the eggs failed to develop, 

 but about one fourth as many formed mem- 

 branes under the influence of the solutions 

 as were formed about fertilized eggs. After 

 the formation of the membranes if the egg's 

 are placed in hypertonic sea-water, 8 c.c- 

 10 c.c. of 2.5 m NaCl or KCl -f 50 c.c, sea- 

 water for 30 minutes and are then brought 

 back into normal sea-water, development con- 

 tinues. Nearly all of the eggs which have 

 formed a membrane become pear-shaped, show- 

 ing a rhizoidal papilla, and by next morning 

 have cleaved. The rhizoidal cell is cut off and 

 one or more cleavages have taken place in the 

 other portion of the sporeling. If the cul- 

 tures are properly aerated, sporelings develop 

 resembling in every respect those grown from 

 fertilized eggs. In place of sea-water contain- 

 ing a fatty acid, solutions of various other 

 cytolytic substances were used, but none stim- 

 ulated membrane formation or development 

 as well as the acids. 



With regard to the first formation of the 

 cell-wall over the surface of isolated masses of 

 plant protoplasm, it is usually attributed to a 

 process of secretion by the outer layer. That 

 the process is a rapid one is shown by the fact 

 that in Fxicus eggs a cell-wall is formed in ten 

 minutes after the entrance of the sperm. 

 Cell-wall formation may also be artificially in- 

 duced, as shown above, by various substances. 

 In some cases a cell-wall may appear under 

 certain conditions on the surface of plasmo- 

 lysed protoplasts in fifteen minutes, as has 

 been shown by Klebs, Palla and others, while 

 in other cases hours are required for wall for- 

 mation. It would appear that the action of 

 the acids in inducing a cell-wall to be formed 

 about the unfertilized Fucus eggs is similar 

 to the action which calls forth membrane for- 

 mation in the animal egg. Considerable evi- 

 dence exists indicating that the essential con- 



