TRANSACTIONS OF SECTION K. 803 



As with different animal tissues, three types of responses have been obtained 

 with plants : (1) Uniform responses ; (2) responses exhibiting fatigue ; and 

 (3) responses exhibiting ' staircase ' effect. Singly inefiective stimuli become effec- 

 tive by summation. Under continuous stimulation a maximum effect is obtained. 

 Increasing stimulus produces increasing response, which tends to approach a limit. 

 As regards the effects of temperature on response, the response is at its maximum 

 at the optimum temperature, the response declining above and below the optimum. 

 The response disappears at the death-points. By no other method can the death- 

 points be determined with such an exactitude. Under certain conditions a 

 diphasic variation is obtained. Ordinary plants exhibit electrotonus. Ansestbetics 

 gradually depress response ; poisons abolish it altogether. The effect of the latter 

 sometimes depends on the dose, a small dose producing the opposite effect of stimu- 

 lation. These and other effects obtained with plants are strictly correspondent 

 with the effects obtained in the animal tissues. 



2, The Movements of the Floiver-buds o/ Sparmannia africana. 

 By RiNA Scott, 



Sparmannia afrioana is a common greenhouse plant, which was introduced 

 from the Cape into Europe in 1 790. 



It is well known to the botanist on account of the curious movement of its 

 stamens, which when touched gradually move away from the stigma, leavino- it 

 exposed and ready for fertilisation by bees. A paper was written on the subject 

 by Ch. Morren as early as 1841. 



The following observations are on the movements of the flower-buds and 

 flowers up to the time of the setting of the fruit. 



At first the buds hang all in one plane ; each hud has a joint on the stalk, 

 which is much swollen below the flower. This joint regulates the position of the 

 bud, flower, or fruit at different times of its development, and it is here that the 

 fruit is detached when ripe. 



Three complete inflorescences were drawn from bud to fruit, from February 25 

 to May 1902, every day and every night, and from these data the following 

 results were obtained. 



The flower-stalk circumnutates and grows during flowering on an average 

 If in. (4'4 cm.) in height ; the flower-bud rises 3 inches (7'5 cm.) in height. 



The buds rise one by one from the drooping position to the horizontal ; then 

 make a sharp curve inwards, and just before flowering the bud hangs down in an 

 exactly vertical position, which is attained by the movement at the joint. The 

 flowers open during sunlight at a temperature not below G0° F. (15-5 C), so that 

 on a cold day perhaps only one flower, while on a hot day three or four may be open 

 at the same time. 



On a sunny, hot day the flowers open very quickly. One bud began opening at 

 12 P.M., temperature 70° F. (21'1 C), and was completely open at 2.5 p.m., 72° F. 

 (22-2 C.) ; asleep at 6 p.m. The bud, however, will not go on opening if for any 

 reason the temperature falls below 60° F. (15-5 C). One bud began opening at 

 10.50 A.M., temperature 72° F. (22-2 C), on a bright, sunny day; at 11 a.m. it had 

 put up two sepals ; at 12.10, 66° F. (18-8 0.\ it was putting up a third, when a 

 hailstorm reduced the temperature below 60° F. (15'5 0.) ; at 12.40 p.m., 66° F. 

 (18-8 C), it put up a third sepal, when another hailstorm at 2.20 again reduced the 

 temperature, and the flower closed for the night. 



Every night the flowers go to sleep ; the youngest go to sleep first. The flower 

 is bent downwards at the joint and first the petals close, one at a time, and then 

 the sepals. A young flower may go to sleep as early as 6 p.m., while an old one 

 may not he asleep by 10.30 p.m. 



"The usual hour for waking is about 9 a.m. The flower begins opening soon 

 after sunrise. On March 23, at 6.40 a.m., the petals began to expand, temperature 

 48° F. (9° C), and the flower was full open at 9 a.m. This is illustrated by a long 

 series of drawings. 



3 F 2 



