OUTLINE OF STRUCTURAL BOTANY 25 
that they do not have the envelopes which we have called the 
perianth, the calyx and the corolla, the organs which, as has been 
remarked above, are, by the casual observer regarded as the flower. 
But when all these parts are present, calyx, corolla, stamens and 
pistils we have not only a perfect but a complete flower. 
The calyx or outer circle of the perianth has ordinarily the color 
of leaves and appears as a little star-shaped circlet or cup-like 
receptacle at the base of the flower or extending upon the corolla 
enfolding it to a greater or less extent. (Fig 28.) 
In some cases, however, the calyx is not green like the leaves 
but takes on the vivid colors which we are accustomed to find 
associated with the petals. In some instances the calyx may re- 
semble the existing petals with which such sepals are generally 
alternate as in the case of the lily where the sepals are petaloid, 
alternate with the real petals and resembling them in size, form 
and color, the three sepals and the three petals uniting in an 
apparent bell-shaped corolla. 
But the calyx may so far usurp the place of the corolla as to 
30. Polypetalous flower of Chickweed, with 5 sepals, 5 petals and 10 stamens. 
31. Apetalous flower of Thalictrum, with 5 sepals, no petals and many stamens. 
32. Choripetalous flower of Ranunculus. 
33- Gamopetalous flower of Convolvulus. 
entirely supplant it and assume the color, the delicacy of texture 
and the brilliancy of hue of the suppressed corolla. In the flower 
of the clematis (Fig 27) we have an instance of this usurpation 
in which the petals are so nearly suppressed that they appear only 
as rudimentary bodies while the sepals spread out as a broad white 
or purple crown. The shining yellow cup of the swamp marigold 
or american cowslip is another familiar instance for the usurpation 
of the function of the corolla by the calyx. The calyx is not sup- 
planted by the corolla and when there is but a single envelope in 
the perianth we know that it is the calyx. In the flower of the 
columbine we have ten members of the perianth all colored. The 
five petals resemble little cornucopias while the five sepals have 
more nearly the ordinary form of petals. 
The calyx, like the corolla, may be unsymmetrical and like the 
petals of the corolla the sepals may be concresently united into a 
single tube. (Fig. 29.) 
