286 PHYLUM XIV. ANTHOPHYTA 
cup (‘‘receptacular cup”). In such a typical flower 
as a Buttercup (Ranunculus) this axis is globular. 
517. In the Buttercup the globular axis is spirally 
studded with many carpels (simple pistils) each consisting 
of a closed cavity below (ovary), gradually tapering 
above to the soft terminal part (stigma). 
WEY, y/7 When young the carpel (megasporophyll) 
“SS is an open, flattish, leaf-like structure, but 
Vertical plan’ of 28 it grows larger its margins curve up- 
Ranunculus ward until they meet and grow together. 
While the carpel is closing, an ovule grows 
out from the base, and becomes enclosed by the carpel 
walls. 
518. Below the globular head of carpels (pistils) are 
several rows of stamens spirally encircling the axis. Each 
stamen is a stalked, somewhat flattish structure (micro- 
sporophyll), bearing four elongated, parallel sporangia 
which contain microspores (pollen). Commonly the 
stalk is called the filament, and the four sporangia to- 
gether, the anther. The sporangia (pollen sacs) split 
longitudinally at maturity and permit the escape of the 
pollen. 
519. Still lower on the flower axis are two series of 
leaf-like structures also spirally arranged, constituting 
the perianth. The upper series includes five rounded, 
yellow petals, the whole being known as the corolla. 
The lower series is made up of five pointed, green sepals, 
this being known as the calyx. 
520. The purpose of a flower is the production of 
seed, and in the Buttercup this is accomplished as 
follows: 
521. In the ovule (megasporangium) an axial spore 
mother cell (archespore) arises, and later this divides 
into four young cells (megaspores), but only the deeper 
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