Macfarlane, The Sensitive Movements of some Flowering Plants. 145 



plant 2 was almost closed, plant 3 and exposed ones were fully 

 threefburths closed, plant 4 was barely one-third closed. At 7:45 

 the leaflets of 4 were deflexed throug 75°, and when next examined 

 at 9:30 they were fully deflexed. 



October 3rd. The sky was heavy and the atmosphere 

 was very moist and dense tili near 11 a. m. By 11:30 the sun 

 had broken through at intervals. From 12:30 tili 2:45 the sun 

 was bright and pretty intense, but thereafter it was clouded over 

 tili 3:50; from then tili sunset it shone brightly. At 12:45 plants 

 1, 2 and 3 showed flat leaflets, but those of 4 had already de- 

 flexed through 10°. At 1:30 p. m. 1, 2 and 3 were as betöre, 

 but 4 was deflexed 45°. At 3:10 it had recoveied to the extent 

 of 10 — 15° in most of its leaflets, and at 4 it was deflexed only 

 to 15° on the average. It continued to expand, though shone 

 on by the slanting and subdued rays, tili at 4 : 30 the leaflets 

 were flat. 



At 5 p. m. plant 1 showed slight nyctitropic movement, 

 at 5:20 those in the open, and at 5: 30 plant 2 moved. At 5:50 

 plant 3 had started, and at 6:20 plant 4. The füll nyc- 

 titropic position was very slowly reached by 2, 3 and 4, for 

 while exposed plants and 1 had deflexed through 90° or thereby 

 by 6 : 20, plant 2 was deflexed 60°, plant 3 about 35°, and 4 had 

 just started. At 8 p. m. 2 was deflexed, 3 was two-thirds and 4 

 was fully one third closed. At 9 all had closed. The rather 

 sudden and considerable difference between the high day tem- 

 perature (28° C at 5 p. m.) and that from 6 p. m .(23° C) 

 onwards, in all probability explains the very sluggish nyctitropic 

 movement just recorded, for the writer has since proved that 

 under similar temperature conditions, the behavior is in no way 

 different, but if the screened plants are brought into a warm green- 

 house about 6:30 nyctitropic movement is at once accelerated. 



Before summarising the abovedetails, referencene may bemade 

 to certain histological conditions studied during the progress of 

 the experiments. Some observers have held that loss of water is 

 the primary cause of the paraheliotropic position, and it has been 

 asserted that the stomata are then closed. Though Oltmanns', 

 experiments and my own prove that the amovement is directly due 

 to changes in the pulvinus cells, other weighty reasons can 

 be advanced against the view that inere loss of water b rings 

 about the change. Plants growing in a dry place under tree shade 

 at 29—32° C and fanned by a breeze might then be expected to 

 show greater paraheliotropic movement than others in sunlight 

 at 26. 5—29° C, and with'the air still. But this is not so. Again 

 while exposed plants at 26—29° C show decided movement in 

 direct sunlight, others under red or yellow screens remain expanded 

 at 35 — 38° C It seemed advisable, therefore, to obtain data as to 

 the behavior of the stomata at different times and under different 

 screens. Records will only be given at present for Cassia 

 nictitans and C. cliamaecrista. In the former, stomata are largely 



Botan. Centralbl. Bd. LXI. 1895. 10 



