1877. ] Variation in Æstivation. 259 
Thirteen were represented by Figure 33, six 
by Figure 34, five by Figure 35, four by Fig- 
ure 86, three by Figure 87, three by Figure 38, \ 
three by Figure 39, three by Figure 40, three 
by Figure 41, two by Figure 42, two by Figure Met j 
43, two by Figure 44, and one by Figure 45. : 
With reference to the Cruciferæ, we find in volume i. of 
Gray’s Genera of North America this sentence: “In æstiva- 
tion, the petals are imbricated with usually one exterior, two 
half exterior and half interior, and the fourth wholly interior, or 
else they are regularly convolute.” Le Maout and Decaisne say, 
“Petals variously imbricate in bud.” Bentham and Hooker’s 
Genera Plantarum says, “ Petals convolute or imbricated with 
one exterior and the fourth interior.” Neither of the above 
quotations expresses the arrangement for the order. The first 
comes the nearest because it is the most general of all. 
Instead of twelve modes of arrangement for the petals of the 
fifty flowers mentioned, no doubt the variations would be consid- 
erably increased if the position of each petal were observed in its 
relation to each sepal. 
Cleome integrifolia has four small sepals early open in the 
bud, variously imbricated. The four petals of one hundred flow- 
ers were arranged as follows : — 
Fig. 46. Fig. 47. Fig. 48. Fig. 49. 
e (3 E e 
Two species of Rosacez belonging to two dif- Hs, ai 
erent tribes were examined, namely, Spiræa urtici- 
folia and Agrimonia Eupatoria. The Spiræa 
noticed has valvate sepals. The pedicels are too f - 
long to make it easy to discover which sepal is 
next to the axis. The tips of the petals overlap 
each other in the bud, making it quite easy to 
determine their relative position. Thirty-three buds were exam- 
ined, showing fifteen different combinations or sorts of æstiva- 
tion for the petals, without taking into consideration the posi- 
tion of each with reference to the axis. None were valvate nor 
regularly conyolute, yet, I doubt not, they may be found. 
