THE FLOWER. 
75 
ated near the margin of the receptacle are known as 
ray-flowers, and because they possess more or less strap- 
shaped corollas are also known as ligulate flowers. 
Those occupying the central portion of the receptacle 
are known as disk-flowers, or tubular flowers, because of 
the tubular shape of the corolla. Most of the Com- 
positse possess both ligulate and tubular flowers, as 
arnica, matricaria, the common daisy, etc. A number 
of the other members of the family have only ligulate 
flow'ers, as chicory and dandelion ; and a relatively few 
have only tubular flowers. 
(c) PREFLORATION OR ESTIVATION. 
Prefloration or estivation is the arrangement of the 
parts of the flower — more especially the calyx and 
corolla — in the bud. Some of the terms used in this 
connection are also employed in the study of verna- 
tion. The following are some of the terms which are 
employed : Valvate, when the sepals or petals meet each 
other at the edges, as in Malvaceae ; imbricated, when the 
sepals or petals overlap each other, as in the Magnolia- 
ceae; plicate or plaited is applied to petals when they are 
united and folded together, as in Convolvulus and Datura. 
The sepals and petals do not necessarily possess the 
same arrangement, as in the Onagraceae, where the 
sepals are valvate and the petals are convolute. 
Furthermore, in addition to the principal types of 
estivation and vernation already given, there are a 
number of special modifications of these, depending 
upon the number and arrangement as well as direction 
of the overlapping parts of the flower or leaf-bud. 
(d) ANTIIOTAXY. 
Just as a flower may consist of one or more parts, so 
a flower-branch may bear more than one flower. The 
