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Smith : Peculiar Case of contact Irritability 191 



were in the same plane, whereas normally but two should be. In one 

 pot all seven which germinated were in the same plane ; in other 

 cases five or six out of seven. Some in each pot had the epicotyl 

 twisted, showing the adjustment was not the result of the position 

 in which the seeds were planted. To investigate this more conclu- 

 sively, sets of beans were planted in different ways. 



(i) In a circle but with hypocotyl of each of the eight beans 

 pointing in the same direction (Fig. 2). Of the six which had 

 germinated on January 27th and unfolded their first leaves all were 

 in the same plane (Fig. 3). January 30th, eight were large enough 

 to be diagrammed ; four were in the same plane, four others were 

 in a plane at about an angle of 15 from this (Fig. 4). 



(2) Twelve beans were planted in a cross, but with the hypo- 

 cotyl of each turned in the same direction (Fig. 5). The resultant 

 position is shown in Fig. 6. . A 12-inch pot was used in this 



(3) Nine beans were planted in a straight line, but with the 

 hypocotyls turned in the same direction and toward each other 

 (Fig. 7). . The result is shown in Fig. 8. If a very large pot was 

 used where no two seedlings could touch, there was no such ad- 

 justment (Fig. 9). 



Other pots were planted with hypocotyl directed up or down, 

 out or in, also with seeds on flatter surface and hypocotyls turned 

 ■in different ways. There was no difference in the resultant posi- 

 tions. The position of planting, therefore, does not determine the 

 adjustment, for good cases of parallelism in the petioles were 

 found, whatever the original positions of the seeds. Therefore, 

 the resultant plane is not brought about by internal causes, but is 

 a response to external stimuli. 



To test varying thermotropism and hydrotropism in the box, 

 pots of beans were placed in different parts of the box. They 

 continued to set their leaves in planes, bearing no constant rela- 

 tion to the sides of the box. Two pots also were placed in an- 

 other case made of glass and darkened ; one ppt put on a clinostat 

 revolving once in fifteen minutes, the other kept stationary. Of 

 the eight beans which germinated on the clinostat six were in the 

 same plane, although the leaves of one were not quite unfolded ; 

 one was not free from the cotyledons and one was at right angles. 



