1877. ] Variation in Aistivation, 261 
Of thirty-eight buds of @nothera biennis thirty were convolute 
to the right ; three buds had one petal outside and the rest spi- 
rally turned to the right ; two buds had one petal outside and the 
rest spirally turned to the left; two buds had one petal outside 
and its opposite one inside; one bud had one petal outside, the 
numbers running thus, 1, 3, 4, 2, to the right. 
Of the order Asclepiadacee with reference to xstivation Dr. 
Lindley in Vegetable Kingdom says, “ Estivation of corolla im- 
bricated, very seldom valvular.” Dr. Gray in his Manual of Bot- 
any, last edition, says, ‘‘ This order has commonly a valvate co- 
rolla which separates it from Apocynacew which has a convolute 
corolla.” In the American Journal of Science, November, 1875, 
Dr. Gray says, “ The type of the latter [ Asclepias], and the com- 
mon disposition when the parts are five, is with two pieces exte- 
rior, the third exterior by one edge and interior by the other, and 
two wholly interior.” In other words, the petals are quincuncially 
arranged, the same as alternate leaves on the stem of a cherry- 
tree. Le Maout and Decaisne say, “ Corolla usually contorted.” 
Robert Brown, who gave especial attention to this order, says, 
“ Astivation of corolla imbricated, rarely valvate.” 
My first supposition was that I had examined a lot of excep- 
tions to the general rule as stated by such good authority as 
Gray, especially as it is given as a distinctive mark to separate 
two related orders. On examining the other authors, I venture 
to give the results of the number of buds and the name of the 
Species examined. 
At the first glance, the corolla of Asclepias and Acerates seem 
to be valvate in the bud, but on looking eloser, all I have seen 
are unmistakably convolute. 
The petals of thirty buds of-Aselepias incarnata were convolute to right. 
x ke e O74 ; «“ “ “ 
variegata 
bi five ti Pia 3 tuberosa f t “ “ 
id five “ see purpurascens t “ “ 
Teil five i“ ee phytolaccoides “ . 
"= five c = 66 Cornuti “ “ + 
ad seven “ = é verticillata He ie sg 
7 five “ = Acerates viridiflora 5 y t 
The results, it will be seen, correspond with the account of 
Le Maout and Decaisne. Probably, Dr. Gray bases his descrip- 
tion on other species than those to which I have referred. ; 
In the order A pocynaceæ, of forty-three buds of Apocynum an- 
drosæmifolium, I found the petals all convolute to the right. 
Five buds of A. cannabinum were the same. In nine buds of 
the former, the sepals were quincuncial to the right, in five buds 
