138 Macfarlane, The Sensitive Movements of some Flowering Plants. 



Yellow glass — red slightly obstructed, orange and yellow 

 unobstructed, yellow-green largely through, blue-green, blue and 

 violet cut out. 



Green glass: — red, orange and yellow cut out, green un- 

 obstructed, green-blue slightly through, blue and violet cut out. 



Blue glass: — red, orange, yellow and green cut out, ( blue 

 and violet through. 



The experimental results recorded below were begun on 

 September 4th and continued, with some interruptions, tili October 

 3rd. They have been selected in preference to others made earlier 

 in the season, as showing the behavior alike during high, medium, 

 and rather low temperatures. It should be emphasized, however, 

 that when the temperature falls considerably and pretty continu- 

 ously below a given Optimum the movements become quite 

 nnreliable. One illustration may be cited from a plant that has 

 been extensively used during my inquiries. Oxalis strieta will 

 grow and remain healthy looking for three or four weeks under a 

 day temperature of 15 — 16° C, and a night temperature of 8 — 9° C T 

 but the sensitive relations are then greatly disturbed and irregulär. 

 With a day temperature of 21 — 27 ö C and a night temperature of 

 17 — 18° C, the plant truly flourishes. 



Cassia nictitans and C. chamaecrista. 



One September 4th vigorous plants of each of the above 

 were selected from others growing alongside, and covered with the 

 colored screens already described. Except that it is less sensitive 

 and therefore more sluggish in its response to Stimuli, the latter 

 species behaves fundamentally like the former, so that occasional 

 reference only will be made to it. The plants were fully exposed 

 to the sun's rays, and grew in a light sandy soil from whose sur- 

 face the rays were strongly reflected. 



At 2 p. m. on the above date the screens were arranged under 

 a diffuse light but exposed to a temperature of 32 ° C in the 

 brightest light, and 29.5 ° C in the shade. The high temperature 

 but diffuse light was due to a hot sun attempting to shine through 

 a smoke cloud, that had been blown dow r n from tired forests in 

 the interior of the State. The leaflets at 2 p. m. were almost flat. 

 By 2:30 the leaflets of 1 and 2*) had inflexed through an angle 

 of 45°, those of 3 through an angle of 15°, and those of 4 were 

 unaltered. By 3:30 the leaflets of 1 and 2 were almost closed, 

 those of 3 were inflexed 60°, those of 4 were unaltered. At 5 

 p. m. the leaflets of 1, 2 and 3 were closed, those of 4 were still 

 unaltered. At 5 : 30 the leaflets of plants in the open began to 

 show nyetitropie movement, as did those of 4 by 5:45. At 6:10 

 all had closed. The inflexion of plants 1 and 2 during daylight aecords 

 with Sachs' Statements for Mimosa pudica ; but the writer has since 

 proved that had the plants been screened at 8 or 9 a. m., the 



*) In speaking of screened plants hereafter those under red screen will 

 be designated 1, under yellow 2, under green 3, and under blue 4. 



