506 Plant Physiology 



nodes ; pin the basal node to a cork or block of wood and follow 

 the process of erection. 



With the special instructions given determine the behavior of 

 roots and shoots of seedlings when gravity is equalized through 

 vertical rotation upon the klinostat. 



Chemotropism.- -The existence of positive and negative chem- 

 otropism would seem to be established and some of the chemo- 

 tropic relations of pollen-tubes may be conveniently and easily 

 observed. Utilize pollen known to germinate freely, such as 

 that of Tradescantia virginica and Narcissus Tazetta and prepare 

 hanging-drop cultures as for pollen germination. When the 

 grains begin to germinate, introduce into the drops bits of the 

 stigma of the plant from which the pollen was taken. Ascer- 

 tain if these stigma bits or if particles of any vegetable proteins 

 (albumins and globulins) exert any influence on the direction of 

 growth of the tubes. 



If time for more extensive study is available, consult the paper 

 by Lidforss (or follow special instructions), employ Pfeffer's 

 capillary tube method, and install the necessary experiments. 



Growth and movement of tendrils. - - Utilizing any tendril- 

 bearing plant available in the greenhouse or field, select several 

 tendrils about one fourth grown, mark off into ten or twenty 

 spaces by means of India ink, and determine the region and 

 period of growth, also the daily percentage increase in the differ- 

 ent longitudinal segments. 



Review in suitable literature the more extensive accounts of 

 tendril movements, and make an extended observation upon the 

 behavior of one type, presenting the results in the form of a 

 report. 



REFERENCES 



BOSE, J. C. Plant Response. 781 pp., 278 figs., 1906. 

 DARWIN, CHARLES. The Power of Movement in Plants. 592 



pp., 1885 [Appleton]. 

 DARWIN, CHARLES and FR. The Movements and Habits of 



Climbing Plants. (2d Ed.) 208 pp., 1884 [Appleton]. 



