Chap. VII. SLEEP OV LEAVES. 343 



IS much variability in the positioQ of the leaves at night on the 

 same plant ; some remaining with their leaflets almost horizontal, 

 others forming more or less highly inclined or vertical stars, and 

 some with all their leaHets sloping downwards, as in our first 

 class of cases. It is also a rbmarkable fact, that although all Iho 

 plants produced from the same lot of seeds were identical in 

 appearance, yet some individuals at night had the leaflets of all 

 their leaves arranged so as to form more or less highly inclined 

 stars ; others had them all sloping downwards and never forming 

 a star; and others, again, retained them either in a horizontal 

 position or raised them a little. 



We have as yet referred only to the different positions of tne 

 leaflets of L. pabesceiis at night ; but the petioles likewise diffeif 

 in their movements. That of a young leaf which formed a 

 highly inclined star at night, stood at noon at 42° above the 

 horizon, and during the night at 72°, so had risen 30°. The 

 petiole of another leaf, the leaflets of which occupied a similar 

 position at night, rose only 6°. On the other hand, the petiole 

 of a leaf with all its leaflets sloping down at night, fell at this 

 time 4°. The petioles of two rather older leaves were subse- 

 quently observed ; both of which stood during the day at exactly 

 the same angle, viz., 50° above the horizon, and one of these rose 

 7°-8°, and the other fell 3°— 4° at night. 



We meet with cases like that of L. pubescens with some other 

 species. On a single plant of L. mutabilis some leaves, which 

 stood horizontally during the day, formed highly inclined stars 

 at night, and the petiole of one rose 7°. Other leaves which 

 likewise stood horizontally during the day, had at night all their 

 leaflets sloping downwards at 46° beneath the horizon, but 

 their petioles had hardly moved. Again, L. luk-us offered a still 

 more remarkable case, for on two leaves, the leaflets which stood 

 at noon at about 45° above the horizon, rose at night to 65° and 

 69°, so that they formed a hollow cone with steep sides. Four 

 leaves on the same plant, which had their leaflets horizontal at 

 noon, formed vertical stars at night; and three other leaves 

 equally horizontal at noon, had all their leaflets sloping down- 

 wards at night. So that tbe leaves on this one plant assumed 

 at night three different positions. Though we cannot account 

 for this fact, we can see that such a stock might readily give 

 birth to species having widely different nyctitropio habits. 



Little more need be said about the sleep of the species of Lu- 

 pirnis ; several, namely, L. polyphyllus, nanus, Menziesii, speciostis, 



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