218 CIECUMNUTATION OF STOLONS. Chap IV, 



on a cloudy day, became distinctly curved towards the light, and 

 were therefore heliotropic. Close in front of the tips of the 

 prostrate stolons, a crowd of very thin sticks and the dried 

 haulms of grasses were driven into the sand, to represent the 

 crowded stems of surrounding plants in a state of nature. This 

 was done for the sake of observing how the growing stolons 

 would pass through them. They did so easily in the course of 

 6 days, and their circumnutation apparently facilitated their 

 passage. When the tips encountered sticks so close together 

 that they could not pass between them, they rose up and passed 

 over them. The sticks and haulms were removed after the 

 passage of the four stolons, two of which were found to have 

 assumed a permanently sinuous shape, and two were sti'l 

 straight. But to this subject we shall recur under Saxifraga. 



Saxifraya sarmentosa (Saxifrageae). — A plant in a suspended 

 pot had emitted long branched stolons, which depended Uke 



Fig. 88. 



Saxifraga sarmentosa: circumnutation of aa inclined stolon, traced in 

 darkness on a horizontal glass, from 7.45 a.m. April 18th to 9 A.M. or 

 9th. Movement of end of stolon magnified 2-2 times. 



threads on all sides. Two were tied up so as to stand vertically, 

 and their upper ends became gradually bent downwards, but so 

 slowly in the course of several days, that the bending was pro- 

 bably due to their weight and not to geotropism. A glass fila- 

 ment with little triangles of paper was fixed to the end of one of 

 these stolons, which was 17J inches in length, and had already 

 become much bent down, but still projected at a considerable 

 angle above the horizon. It moved only slightly three times 

 from side to side and then upwards ; on the following day 



