1.26 COTYLEDONS SENSITIVE Chap. IL 



pin in this part, they rose up vertically ; but the blade was found 

 also to be sensitive, care having been taken that the ptilvinus 

 was not touched. Drops of water placed quietly on these coty- 

 ledons produced no effect, but an extremely fine stream of water, 

 ejected from a syringe, caused them to move upwards. When 

 a pot of seedlings was rapidly hit with a stick and thus jarred, 

 the cotyledons rose slightly. When a minute drop of nitric 

 acid was placed on both pulvini of a seedling, the cotyledons 

 rose so quickly that they could easily be seen to move, and 

 almost immediately afterwards they began to fall; but the 

 pulvini had been killed and became brown. 



The cotyledons of an unnamed species of Cassia (a large tree 

 from S. Brazil) rose 31° in the course of 26 m. after the pulvini 

 and the blades had both been rubbed during 1 m. with a twig ; 

 but when the blade alone was similarly rubbed the cotyledons 

 rose only 8°. The remarkably long and narrow cotyledons, of a 

 third unnamed species from S. Brazil, did not move when their 

 blades were rubbed on six occasions with a pointed stick for 

 30 s. or for 1 m. ; but when the pulvinus was rubbed and slightly 

 pricked with a pin, the cotyledons rose in the course of a few 

 minutes through an angle of 60°. Several cotyledons of 

 C. negleda (likewise from S. Brazil) rose in from 5 m. to 15 m. to 

 various angles between 16° and 34°, after being rubbed during 

 1 m. with a twig. Their sensitiveness is retained to a somewhat 

 advanced age, for the cotyledons of a little plant of C iicglecta, 

 34 days old and bearing three true leaves, rose when lightly 

 pinched between the finger and thumb. Some seedlings were 

 exposed for 30 m. to a wind (temp. 50° P.) sufiiciently strong to 

 keep the cotyledons vibrating, but this to our surprise did not 

 cause any movement. The cotyledons of four seedlings of the 

 Indian C. c/laucaweve either rubbed with a thin twig for 2 m. or 

 were lightly pinched : one rose 34° ; a second only 6° ; a third 

 13°; and a fourth 17° A cotyledon of C. florida similarly 

 treated rose 9° ; one of 0. corymhosa rose li°, and one of the 

 very distinct C. mimosoides only 6°. Those of C. pubescens did 

 not appear to be in the least sensitive ; nor were those of C. 

 nidosa, but these latter are rather thick and fleshy, and do not 

 rise at night or go to sleep. 



Smitliia sensitiva. — This plant belongs to a distinct sub-order of 

 the Leguminosse from Cassia. Both cotyledons of an oldish 

 seedling, with the first true leaf partially unfolded, were rubbed 

 for 1 m. with a fine twig, and in 5 m. each rose 32°; thoj 



