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AMERICAN NATURALIST. 
Vol. VIIL.— DECEMBER, 1874.—No. 12. 
CT VTORD OD D> 
’ IMBRICATIVE ZESTIVATION. 
- BY A. P. MORGAN. 
1. Tue arrangement of the different parts of the flower in the 
bud is called œstivation or prefloration. Aistivation has refer- 
ence chiefly to the relative arrangement in the bud of the sepals 
_ and petals. The æstivation of the floral envelopes passes by 
= Several gradations from the regular alternate arrangement of 
leaves, in which the parts are situated at different heights one 
above another, to the complete whorled arrangement in which the 
parts are all placed at the same level, edge to edge. 
2 2. There are distinguished three principal kinds of sstivation 
_ denominated respectively the imbricative, the contortive and the 
= Valvular. The latter presents no variety except the infolding of 
= the edges of the leaves which, however, does not concern their 
= Yelative arrangement in the bud; and contortive æstivation ex- 
hibits no variation except in the direction of the twist which may 
be either from left to right or from right to left. It is our pur- | 
Pose to give an analysis of imbricative sstivation and to endeavor 
to systematize its variability. 
3. In imbricative estivation some parts of the floral whorl over- 
lie others like shingles on a roof: that is, certain parts are wholly 
external while others are wholly internal. There is usually a more 
_ less evident spiral arrangement of the parts; the spiral making 
_ be or more turns to form the whorl. When the direction of the 
4 
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aa Entered, according to Act of Congress, in the year 1874, by the PEABODYZACADEMY OF: 
SCIENCE, in the Office of the Librarian of Congress, at Washington. i J 
AMER. NATURALIST, VOL. VIII. 45 (705) 
