126 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 pulvinus 

 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. neghcta (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 O. neglecta, 

 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 F.) sufficiently 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. ylauca were 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 C. corymbosa rose 7J, 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. 

 nt.dosa, but these latter are rather thick and fleshy, and do not 

 rise at night or go to sleep. 



Smithia 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; they 



