308 MODIFIED CIKCUMNUTATION. Chap. VI 



been described in the first chapter. The experiment was a 

 superfluous Dne, but pots with seedlings of 0. rosea and flonbunJa 

 were turned upside down, as soon as the cotyledons began to 

 show any signs of sleep, and this made no difference in their 

 movements. 



Leguminosas. — ^It may be seen in our list that the cotyledons 

 of several species in nine genera, widely distributed through- 

 out the Family, sleep at night ; and this probably is the case 

 with many others. The cotyledons of all these species are pro- 

 vided with a pulvinus; and the movement in all is continued 

 during many days or weeks. In Cassia the cotyledons of the 

 ten species in the list rise up vertically at night and come 

 into close contact with one another. We observed that those 

 of C. florida opened in the morning rather later than those of 

 C. glaiica and pubescens. The movement is exactly the same 

 in 0. mimosoides as in the other species, though its subsequently 

 developed leaves sleep in a different manner. The cotyledons 

 of an eleventh species, namely, C. nodosa, are thick and fleshy, 

 and do not rise up at night. The circumnutation of the coty- 

 ledons during the day of G. torn has been described in the first 

 chapter. Although the cotyledons of Smithia scnsitiva rose from 

 a horizontal position in the middle of the day to a vertical one 

 at uight, those of S. Pfundii, which are thick and fleshy, did not 

 sleep. When Mim'sa pudka and albida have been kept at a 

 sufficiently high temperature during the day, the cotyledons 

 come into close contact at night ; otherwise they merely rise up 

 almost vertically. The circumnutation of those of M. pudka 

 has been described. The cotyledons of a Bauhinia from St. 

 Catharina in Brazil stood during the day at an angle of about 

 5'J° above the horizon, and at night rose to 77° ; but it is pro- 

 bable that they would have closed completely, if the seedlings 

 had been kept in a warmer place. 



Lotus. — In three species of Lotus the cotyledons were observed 

 to sleep. Those of L. Jacoboeus present the singular case of not 

 rising at night in any conspicuous manner for the first 5 or 

 6 days of their life, and the pulvinus is not well developed at 

 this period. Afterwards the sleeping movement is well dis- 

 played, though to a variable degree, and is long continued. 

 We shall hereafter meet with a nearly parallel case with the 

 loaves of Sida rhombifulia. The cotyledons of L. Gebelii are 

 only slightly raised at night, and differ much in this respec' 

 from the three species in our list. 



