A CONTRIBUTION TO THE LIFE HISTORY OF 
EUPHORBIA COROLLATA.* 
FLORENCE May LYON. 
(WITH PLATES XXII—XXIV) 
INFLORESCENCE. 
Tue inflorescence of Euphorbia corollata is of the complicated 
form known as a cymose_ umbel. From the axils of bracts on 
the main stem of the inflorescence there arise three to five 
branches, each terminating in a smaller inflorescence called a 
cyathium, still occasionally referred to as ‘‘a flower’’’ ( figs. 12, 
13, 14). ! 
These branches in turn produce bracts with axillary branches 
and terminal cyathia, and so on through four, five, or rarely six 
generations of branches ( fig. rg). As the secondary and ter- 
tiary branches of the inflorescence develop, there is a tendency 
to diminish the lateral members, so that the ultimate branching 
may become dichasial. Again, all the terminal cyathia on the 
branches preceding the penultimate may be lacking. 
THE CYATHIUM. 
The cyathium has every external appearance of a perfect, 
complete flower ( fig. z2). The involucre of five white bracts 
looks like a gamopetalous perianth. At the entrance to the 
tubular portion are developed five glands, which, together with 
five delicate outgrowths of the involucre, nearly block the 
passage. Within this involucre and opposite its component 
bracts are five groups of staminate flowers. A group com- 
monly consists of three members, and each staminate flower is a 
single stamen terminal on a pedicel, and distinguishable exter 
"Contributions from Hull Botanical Laboratory. X. 
* BAILLON: Histoire des plantes 5 ; 109. 1874. E 
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