198 PRACTICAL COURSE IN BOTANY 
flowers, there is little or no difference between the two sets of 
organs. In such cases the calyx and corolla together are 
called the perianth, but the distinction of parts is always 
observed, the outer divisions being regarded as sepals, the 
inner ones as petals. These two sets of organs constitute 
the floral envelopes, and are not essential parts of the flower, 
as it can fulfill its office of producing fruit and seed without 
them. Note their number, mode of attachment to the 
receptacle, and how they alternate with each other. Re- 
move one of the sepals and one of the petals, and notice any 
differences between them as to size, shape, or color. Which is 
most like a foliage leaf? Hold each up to the light and try 
to make out the veining. Is it the same as that of the foliage 
leaves? Ifa light-colored flower is used, examine a specimen 
that has stood in coloring fluid. How many of each set are 
there? 
212. The essential organs. — Next sketch the flower on 
its inner face, labeling the appendages just within the petals, 
stamens, and the central organ 
within the ring of stamens, 
pistil. These are called essen- 
tial organs because they are 
necessary to the production of 
fruit and seed. Note their 
mode of insertion, three of the 
stamens in a flower like the 
star-of-Bethlehem alternating 
273 
270 271 272 274 
Fies. 270-274.— Stamens: 270, a 
typical stamen with the terminal an- 
ther, 6, surmounting the filament, u, 
and opening in the normal manner 
down the outer side of each cell ; 271, 
stamen of tulip tree, with adnate ex- 
trorse anther; 272, stamen of an eve- 
ning primrose (@nothera) with versatile 
anther; 273, stamen of pyrola, the 
anther cells opening by chinks or pores 
at the top ; 274, stamen of a cranberry, 
with the anther cells prolonged into a 
tube and opening by a pore at the apex. 
(After Gray.) 
with the petals, and the other 
three with these and with the 
lobes of the base of the pistil. 
213. The stamens. — No- 
tice whether the stamens are 
all alike, or whether there are 
differences as to size, height, 
shape, color, etc. Do these 
differences, if there are any, 
