Macfarlane, The Sensitive Movements of some Flowering Plants. 139 



leaflets Avould have recovered by early afternoon. In the case of 

 Mimosa, recovery of a screened priraary leaflet takes place within 

 three to four hours. 



September 5th. At 8:30 a. m. the sky was dull aud 

 the air cool. Screened and exposed plants alike showed fully 

 expanded leaflets. At 9 : 30 the sun began to break through the 

 snioke-cloud, and by 10 was shining brightly. The temperature 

 at that tine was 35 ° C in the sun and in the shade 29 ° C. Then, 

 and at 10:30 the temperature inside screen 1 was 37° C when 

 the thermometer was exposed to the brightest red light. The 

 leaflets were either Hat or slightly deflexed*). Under 2 the tem- 

 perature was 40 ° C and the leaflets were flat. The temperature 

 under the green screen was 35.5° C and the leaflets were flat or 

 very slightly inflexed. The temperature under 4 was 37 ° C, and 

 the leaflets were inflexed through an angle of 35 — 40 °. The un- 

 protected plants around had their leaflets inflexed 20 — 35 °, while 

 plants under oak shade near by were flat or very slightly inflexed. 

 The temperature steadily rose tili 1:20, when it was 31.5° C in 

 the shade. All of the plants remained unchanged, except that 

 under the blue screen, whose leaflets formed an angle of 40 — 45 °. 

 Between 1 : 30 and 2 floating clouds pretty steadily subdued the 

 light, and this went on tili sunset. By 2:15 the leaflets under 4 

 were nearly flat, those under 3 were quite flat, those under 2 and 

 1 were chiefly deflexed through 5 — 7°. The leaflets of the 

 exposed plants were inflexed 15 — 20° tili near 3 p. m., but there- 

 after they gradually recovered tili by 4:15 they were flat. By 

 4:15 many of the leaves of 1 had placed themselves in a peculiar 

 and irregulär position, some being strongly deflexed, others ele- 

 vated at angles of 10 — 30°. At 4:30 its leaflets had started 

 slight nyctitropic movement which went on tili 5 : 15 when the 

 leaflets were almost closed. At 4:50 the leaflets of 2 had started, 

 ancl by 5:15 they were fully half closed. Not only did the leaves 

 of 1 move irregularly ; the leaflets of these, and to a less degree 

 those of 2 closed irregularly; that is, while most curved steadily 

 inwards, others were sluggish in action or scarcely moved, so that 

 when the majority of the leaflets had fully closed, a few amongst 

 them remained niore or less expanded. At 5:15 those ot 3 had 

 slightly moved, and so had those of exposed plants. At 5 : 30 

 the leaflets of 3 were almost half closed, while those of 4 were 

 flat. By 6:15 exposed plants, also 1, 2 and 3 showed perfect 

 nyctitropism ; at this time the leaves of 4 were fully half closed, 

 and by 6 : 30 they had entirely closed. 



September 6th. The day was dull and cloudy, though 

 warm. At 9 : 30 a. m. the temperature inside the screens ranged 

 from 30 — 32.5° but from this time on, the leaflets remained flat. 

 Though somewhat retarded over the previous day, all showed nyc- 

 titropism in the order above given. As on the previous day, 



*) The terms „inflexed" and „deflexed" are used here in an exact sense. 



