Comparative Studies on the Rate of Circum- 

 nutation of Some Flowering Plants. 



By Elizabeth A. Simons. 



DURING the spring term of session 1897-98 the Senior 

 and Post-Graduate students of the Botanical Depart- 

 ment began, under the direction of Professor Macfar- 

 lane, a series of experiments on the circumnutation of stems, for 

 comparison of the results with those obtained by Darwin* 

 and more recently in the Botanic Garden of the University 

 by Dr. A. Schively.f 



The writer was asked to continue and extend these results, 

 for five plants specially recorded by Danvin. These are Con- 

 volvulus Scpium, Pliascolus vtdgaris, Loniccra brachypoda, 

 {L. japonka), Wistaria chinensis, and Hunmlus Lupidus. Marks 

 were made at frequent time-intervals on a plate of glass placed 

 directly above the circumnutating tip, and permanent graphic 

 records have been prepared from them. The tables appended 

 to this paper have been compiled from these. 



The shoots were carefully tied to a support, and in most 

 cases three internodes were left free. The records extended 

 over a period of about six months, and thus included times 

 when the sun gave considerable differences of light intensity 

 and of temperature. In this paper no account is taken of light 

 intensity, though data are being gathered which indicate that 

 this is a factor in circumnutation, as is also the relative hygro- 

 metric condition of the atmosphere. It is somewhat unfortu- 

 nate that few details are given by Darwin as to environmental 

 conditions, but the writer regards the relatively higher tem- 

 perature that prevailed during her studies as the main factor 



* Power of Movement in Plants. 



■f Bot. Contrib. Univ. Penn. Vol. I. 



66 



