VARIATIONS AND MOTIONS OF PLANTS. 105 



place if such plants are put into darkness in the day time. 

 Some plants are known to close their leaves on being touched, 

 as the Sensitive plant; and some leaves are put in motion 

 by the most gentle breeze, as the Aspen-tree, the leaves of 

 which are always trembling on the tree, and hence the name 

 tremula. In flowers, a motion is observable in their folding 

 and unfolding, in different periods of the day; an example of 

 this is observable in a pretty green-house plant, the Oxalis 

 versicolor, which opens its flowers in the middle of the day, 

 when the sun shines on it, and the heat is above sixty degrees, 

 but closes when darkness comes on at night ; and on the fol- 

 lowing day the same motion is observable if the sun and heat 

 are congenial, but if not, the flowers remain folded. The 

 most beautiful motion in flowers that I am acquainted with, 

 is exemplified in the Edivardsia grandiflora. This beautiful 

 plant expands its calyx, which is cloven, when the sun shines 

 strongly on it ; from between the calyx, a drop of nectar, or 

 honey appears, and becomes larger as the sun has more influ- 

 ence ; the upper petals of the flower then ascend to catch the 

 honey, and protect the more delicate part of the flower, which 

 in time fully expands ; but so soon as the sun withdraws, the 

 tender parts of the flower close, and the upper petals descend 

 with honey adhering to them, which amasses the whole 

 flower in nectar, a rapid decomposition takes place, and in a 

 few hours the flowers drop from the plants, and putrefactior 

 immediately follows. This fact accounts for the difficult} 

 of obtaining seed from the plant in question. 



