2 Hooker: Physiological observations 



ing was a nutation or a variation movement. Analogy with the 

 behavior of tendrils, which has been thoroughly investigated by 

 Fitting, indicates that the reactions of Drosera are phenomena of 

 growth, and this is substantiated by Batalin's ('77, p. 36) some- 

 what meager measurements. These are, in Pfeffer's words ('06, 

 3: 85), "not fully satisfactory." Although the primary pur- 

 pose of this paper is to settle this point, a number of observa- 

 tions were made during the work which pertain to other matters. 

 These minor points are of some physiological interest and will be 

 mentioned before proceeding to the main discussion. 



2. Material 



The material used was collected during the months of July 

 and August from Beaver Swamp in the city of New Haven, 

 Connecticut. It was found advisable to use only fresh material 

 for experimentation. 



Plants of Drosera rotundifolia and D. longifolia were found 

 growing in Sphagnum. In removing them, large pieces of the 

 substratum were taken along with the plants to prevent injury 

 to the roots and to insure their further development in the labora- 

 tory. Slight injuries to the roots cause the secretion of the glands 

 to stop and render the tentacles inactive, so that they fail to 

 respond to the customary stimuli. The root-hairs are particu- 

 larly remarkable, for they are not restricted to a small region 

 above the root-tip but cover the entire length of the root. They 

 do not die, but continue to grow and function. In this way they 

 increase the effectiveness of the small root-system. 



The plants were placed in flat dishes, made wet with distilled 

 water and covered with bell-jars. Under these conditions the 

 development of the plants was far from normal. The rosette 

 arrangement of the leaves was lost, a typical stem was developed 

 by lengthening of the internodes and every trace of red pigment 

 disappeared. No gradations from purple to green leaves were 

 observed. All the leaves, which unfolded in the moist atmosphere 

 and subdued light of the culture, were green. The size of the 

 leaves diminished and their petioles made a more acute angle 

 with the stem, causing them to point obliquely upward instead 

 of horizontally outward. 



