98 A LABORATORY MANUAL OF BOTANY 
But this perianth is usually differentiated into two sets of 
leaves—an outer green set, known as the calyx, each leaf 
of which is a sepal, and an inner more or less colored set 
known as the corolla, each leaf of which is a petal. Just 
inside the petals are the stamens or microsporophylls, so 
called because they bear the microspores or pollen-grains, 
and inside the stamen group are one or more megasporophylls 
(carpels or pistils), so called because they bear the mega- 
spores—the large cell within the ovule that finally develops 
into the embryo-sac. 
How many sepals, petals, stamens, and pistils are there 
in the flower you have? Is there any regularity in their 
positions? Make a diagram showing the number of each, 
and how they are placed with reference to each other? 
Draw one member of each floral set. Of the stamen, 
the tip part which contains the pollen-grains is the anther, 
and the stalk is the filament. The anther usually contains 
four sporangia. Of the pistil, the swollen part is the ovary, 
the elongated part the style, and the tip the stigma. Use 
these names in labeling your drawings. 
Remove, examine, and sketch some pollen-grains. Make 
a section across the ovary, and see how the ovules are ar- 
ranged within it. Has the ovary a single cavity or several 
cavities. The presence of several cavities indicates that 
several megasporophylls have united. What is the form of 
the ovule? 
Within the ovule the large spore develops into the em- 
bryo-sac, which contains beside other structures the female 
gamete—the egg. It is evident that the gametophyte stage 
is very brief, and that it is entirely hidden within the ovule. 
The pollen-grain alights upon the stigma and develops a 
pollen-tube, which grows down the style, and finally reaches 
the ovule, which it penetrates, thus reaching the embryo- 
sac. The contents of the pollen-grain have meantime 
formed two male gametes, and when the pollen-tube reaches 
