SATS a oo emer 
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THE AUSTRALIAN NATURALIST. 73 
We are told that Linnaeus formed one at Upsala, and 
attempts in imitation have on several occasions been made 
in Great Britain, with more or less success. The fact, how- 
ever, of the closing is one thing, the explanation of it is 
quite another; and to this last we are endeavouring to 
obtain some information. 
It is interesting to note that while a number of flow- 
ers close because of the removal of the stimulus of the 
solar light, many exhibit a total indifference to it. For 
example, to find the blue-rayed florets of the so-called 
“Oyster Plant’’ or ‘‘Salsify’’? (Lragopogon porrifolius) 
one must visit the neighbourhood of Flemington, or Moore 
Park, very early in the mrning, at least before ten or 
eleven o’clock in the morning, as the flowers are closed 
by noon, though the sun may be bright and shining; hence 
it has received the popular name in the old land of 
“* Johnny-go-to-bed-at-noon.”’ 
Some few years ago, before the new Central Station 
was built, this introduced composite was quite common in 
the Devonshire Street Cemetery, and it is quite common 
on the railway embankments at Campbelltown. 
If the various varieties of flowers are studied, it will 
be found that the phenomenon of the so-called ‘‘sleep’’ 
belongs less to external influences than to some peculiarity 
in the life-history or physiology of the plant. 
Take for example the Native ‘‘Pig’s Face’’ (Mesem- 
bryanthemum aequilaterale), found along our sea shores, 
together with the cultivated species, we find that the flow- 
ers do not expand until the sun is high up in the heavens— 
somewhere about noon. 
It has been suggested that these probably require a 
certain intensity of light and heat. Some species, as, for 
instance, the introduced Scarlet or Purple Pimpernel 
(Anagallis arvensis), open and close with every change in 
the character of the sky. 4 
The Evening Primrose (Oenothera biennis), which is 
common in certain parts of Port Jackson, and many of the 
cactus plants, such as the genus Cereus, cultivated in 
our gardens, open their petals in the evening. 
In many plants, especially those which belong to the 
Pea family (Leguminosae), the leaves close towards even- 
ing and expand in daylight. For example, the various 
species of Medics (Medicago spp.) and Trefoils, or Clo- 
vers (Trifolium spp.), which are naturalised in the Port 
Jackson district, afford an interesting study. 
