There are, however, some other sources of doubt with [page 299] respect to the sleep of cotyledons.  In certain cases, the cotyledons whilst young diverge during the day to only a very moderate extent, so that a small rise at night, which we know occurs with the cotyledons of many plants, would necessarily cause them to assume a vertical or nearly vertical position at night; and in this case it would be rash to infer that the movement was effected for any special purpose.  On this account we hesitated long whether we should introduce several Cucurbitaceous plants into the following list; but from reasons, presently to be given, we thought that they had better be at least temporarily included.  This same source of doubt applies in some few other cases; for at the commencement of our observations we did not always attend sufficiently to whether the cotyledons stood nearly horizontally in the middle of the day.  With several seedlings, the cotyledons assume a highly inclined position at night during so short a period of their life, that a doubt naturally arises whether this can be of any service to the plant.  Nevertheless, in most of the cases given in the following list, the cotyledons may be as certainly said to sleep as may the leaves of any plant.  In two cases, namely with the cabbage and radish, the cotyledons of which rise almost vertically during the few first nights of their life, it was ascertained by placing young seedlings in the klinostat, that the upward movement was not due to apogeotropism.

The names of the plants, the cotyledons of which stand at night at an angle of at least 60o with the horizon, are arranged in the appended list on the same system as previously followed.  The numbers of the Families, and with the Leguminosae the numbers of the Tribes, have been added to show how widely the plants in question are distributed throughout the [page 300] dicotyledonous series.  A few remarks will have to be made about many of the plants in the list.  In doing so, it will be convenient not to follow strictly any systematic order, but to treat of the Oxalidae and the Leguminosae at the close; for in these two Families the cotyledons are generally provided with a pulvinus, and their movements endure for a much longer time than those of the other plants in the list.

List of Seedling Plants, the cotyledons of which rise or sink at night to an angle of at least 60o above or beneath the horizon.

Brassica oleracea.  Cruciferae (Fam. 14).
—­ napus (as we are informed by Prof.  Pfeffer).  Raphanus sativus. 
Cruciferae. 
Githago segetum.  Caryophylleae (Fam. 26). 
Stellaria media (according to Hofmeister, as quoted).  Caryophylleae. 
Anoda Wrightii.  Malvaceae (Fam. 36). 
Gossypium (var.  Nankin cotton).  Malvaceae. 
Oxalis rosea.  Oxalidae (Fam. 41).
—­ floribunda.
—­ articulata. 
—­ Valdiviana.
—­ sensitiva. 
Geranium rotundifolium.  Geraniaceae (Fam. 47).