SUB-KINGDOM I: PHAENOGAMOUS PLANTS
The sleep of cotyledons seems to be a more common phenomenon than that of leaves. The long endurance of the nyctitropic movements when effected by the aid of pulvini indicates, in addition to the evidence already advanced, the functional importance / of such movements to the plant. Leaves were prevented from assuming their nyctitropic position, generally by being fastened with the finest entomological pins to thin sheets of cork supported on sticks. As a general rule, cotyledons which are provided with pulvini continue to rise or sink at night during a much longer period than those destitute of this organ. With Trifolium strictum the blades of the cotyledons rise at night by the aid of their pulvini; whilst the petiole of one cotyledon twists half-round at the same time, independently of its pulvinus. The hypocotyl is slightly sensitive, so that if rubbed with a needle it bends towards the rubbed side.