258 Variation in Æstivation. [May, 
ten, at their tips, showed the left lateral sepal overlapping the 
right; in the other five the right lateral sepal was outside the 
left one. In speaking of the right and left sepals of these flow- 
ers, I refer to them as they appear when holding the flower be- 
fore us with the axis of inflorescence away from or beyond the 
flower. In the hedge-mustard (Si isymbrium officinale) the lateral 
sepals barely meet, making it impossible to tell which would 
overlap if they were longer. Of ten buds of Nasturtium palus- 
tre, seven had the right lateral sepal covering the left; and in 
three, the reverse was true. The estivation of the petals of the 
three preceding species was not easy to determine with certainty, 
as the tips overlapped but very slightly or not at all. 
In Chinese mustard, the æstivation of the sepals was variable, 
much the same as in the other species above noticed. Fifty flow- 
ers were carefully examined. I observed the position of each 
petal with reference to each other petal, and also its position with 
reference to the axis. Each of the four petals, or a correspond- 
ing petal in different flowers, was found outside; each was found 
inside. Bearing in mind, as I think we ought, the position of 
each petal with reference to the axis, I found that the petals of fifty 
flowers were placed in twelve different ways. In the first twelve 
examined, the petals were arranged in eight different ways, as 
follows. The dot indicates the position of the axis : — 
DIO 
Hie ~S as 38. ~ 89. ~ ss 
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