2 PERIODICAL OPENING AND CLOSING OF FLOWERS. 



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not be regarded more properly as a symptom of sleep in plants, 

 than the alternate approximation or divergence of neighbouring 

 leaves, or the folding together of leaflets and other analogous 

 phenomena depending on the position of such organs: exactly 

 as in men and animals, the closing of the eyes is to be regarded 

 rather as a sign of sleep, than the sinking of the hands and the 

 repose of the feet. The strongest argument against a contrary 

 view rests on the fact that plants bear leaves during the whole 

 time of active vegetation, whereas their flowers are of short 

 duration, and that, consequently, observations of the change of 

 position of leaves would be more consistent with a general inquiry 

 into the sleep of plants than those on the phases of blossoms, 

 especially since these can only be made in the case of regular 

 corollae. It may be replied, however, that the changes of position 

 in leaves, as regards the sleep of plants, are so multifarious, not 

 only in different species, but even in different individuals or even 

 different leaves of the same species, that observations on a number 

 of species are not easily comparable with one another, and, more- 

 over, cannot be the object of admeasurement after a definite 

 scale, whereas the phases of blossoms may be regarded as 

 describing the arc of an angle, which in every case admits of 

 an approximate estimation. 



"Nor can periodic phenomena be denied to blossoms because 

 many last no longer than a single day, since those which fade are 

 replaced by new blossoms, which exhibit the same alternations ; 

 and in many cases the same individual corolla? go through the 

 same alternation of phases for many successive days. To this may 

 be added the more important destination of these organs in the 

 economy of the plant, their finer texture, their greater number and 

 variety, circumstances which make them far more fit for the exhibi- 

 tion of vegetable life, than the leaves which are in every respect of 

 inferior dignity. While, however, I leave these and similar 

 questions to the determination of Vegetable Physiologists, I would 

 remark that, in the following results of the phenomena of sleep in 

 plants, the question is confined to the periodic changes in the 

 close or expansion of flowers, while a more complete representa- 

 tion of the subject remains for future inquiry." 



Our author made his first observations in the neighbourhood 

 of Prag, in the year 1840. His immediate object was to note 

 the epochs at which plants go through distinct phases of evolution, 

 and in time, when the number of observations should allow, to 

 distinguish the normal epochs for certain phenomena of develop- 



