CHAP. VI. SLEEP OF COTYLEDONS. 307 



Mirabilis jalapa and lonyiflora (Nyctagineae). The cotyledons, 

 which are of unequal size, stand horizontally during the middle 

 of the day, and at night rise up vertically and come into close 

 contact with one another. But this movement with M. longijlori 

 lasted for only the three first nights. 



Btta, vulgaris (Polygonese). A large number of seedlings were 

 observed on three occasions. During the day the cotyledons 

 sometimes stood sub-horizontally, but more commonly at an 

 angle of about 50 aboye the horizon, and for the first two or 

 three nights they rose up vertically so as to be completely 

 closed. During the succeeding one or two nights they rose 

 only a little, and afterwards hardly at all. 



Amaranthus caudatus (Amaranthacese). At noon the coty- 

 ledons of many seedlings, which had just germinated, stood at 

 about 45 above the horizon, and at 10.15 P.M. some were nearly 

 and others quite closed. On the following morning they were 

 again well expanded or open. 



Cannabis sativa (Cannabineae). We are very doubtful whether 

 this plant ought to be here included. The cotyledons of a large 

 number of seedlings, after being well illuminated during the 

 day, were curved downwards at night, so that the tips of some 

 pointed directly to the ground, but the basal part did not appear 

 to be at all depressed. On the following morning they were 

 again flat and horizontal. The cotyledons of many other seed- 

 lings were at the same time not in any way affected. Therefore 

 this case seems very different from that of ordinary sleep, and' 

 probably comes under the head of epinasty, as is the case with 

 the leaves of this plant according to Kraus. The cotyledons are 

 heliotropic, and so is the hypocotyl in a still stronger degree. 



Oxalis. We now come to cotyledons provided with a pulvinus, 

 all of which are remarkable from the continuance of the nocturnal 

 movements during several days or even weeks, and apparently 

 after growth has ceased. The cotyledons of 0. rosea,floribunda 

 and articulate sink vertically down at night and clasp the upper 

 part of the hypocotyl. Those of 0. Valdiviana and scnsitiva,, on 

 the contrary, rise vertically up, so that their upper surfaces come 

 into close contact ; and after the young leaves are developed these 

 are clasped by the cotyledons. As in the daytime they stand hori- 

 zontally, or are even a little deflected beneath the horizon, they 

 move in the evening through an angle of at least 90. Their 

 complicated circumnutating movements during the day havd 



