Growth and Movement. 103 



growing under normal conditions out of doors. Try to 

 determine what incites some tendrils to twine, and why 

 the tendrils of Virginia creeper grow toward a support. 

 Gently rub the tendrils of squash or wild cucumber on one 

 side with a stick and watch for the result. Inclose some 

 young shoots of Virginia creeper so that they are kept 

 dark, and, after new tendrils have been formed under these 

 conditions, note whether they grow in a different direction 

 from that taken by tendrils which have developed under 

 normal conditions of illumination. 



104. Note the positions of leaves of clover, Oxalis, 

 Amorpha, etc., in the daytime and in the nighttime. Of 

 what use are the observed changes in position ? 



105. Observe the direction taken by the stems of trumpet 

 creeper. Is there any difference in behavior between 

 those stems which bear leaves only and those which bear 

 flowers as well as leaves ? 



1 06. Grow in a greenhouse or under a bell jar seedlings 

 of Mimosa pu^ica, and note the effect of touching the leaf- 

 lets, or of shaking the entire plant. Do the leaflets change 

 their position on being transferred from sunlight to shade, 

 and vice versa ? Do they have distinct positions for night- 

 time and daytime ? Of what use to the plant are the 

 actions observed ? 



107. Mount a young stamen hair of Tradescantia Vir- 

 ginica, or hairs from young portions of the stem of tomato 

 or squash, in a drop of water on a glass slip, and examine 

 under high power of the microscope for streaming motion 

 of the cytoplasm. In removing hairs, some of the tissue 

 to which they are attached should be taken with them in 

 order to prevent their injury. 



1 08. Cut a hole a trifle smaller than a coverglass in a 

 piece of thick felt paper one inch square. Boil the paper 



