FLORAL ENVELOPES.—THE CALYX. 223 
so that it is difficult or almost impossible to say, in many cases, 
where the calyx ends and the corolla begins. The White 
Water-lily (fig. 453) affords a familiar and good illustration of 
this. In some plants, again, the green colour disappears, and 
the calyx becomes coloured with the same tints as the corolla, 
or with some other bright hues. In such cases it is said to be 
petaloid, and the chief distinctive character between it and the 
corolla is then afforded by its position on the outside of the 
latter organ. The Fuchsia, Indian Cress, Columbine, Lark- 
spur, and Monkshood may be mentioned as affording fami- 
har examples of a petaloid calyx amongst Dicotyledons. In 
Monocctyledons generally, as in the Lily, Iris, Tulip, Crocus, 
and Squill (jig. 28), as we have mentioned (page 17), the 
Fig. 453. Flower of the White Water-lily (Vymphea alba) reduced in size, 
After Jussieu. c,c,c,c. The four sepals. p,p,p, p. Petals. e. Stamens, 
The parts on the rignt show the gradual transition from the calyx, ¢, to 
the petals, p, and from these organs to the stamens, e. The stamensfrom 
1 to 5 are gradually more distinctive, 
two floral envelopes are usually coloured, although rarely green, 
and in other respects so closely resemble each other, that 
we then use the collective name of perianth to indicate the 
two whorls taken together. When there is but one whorl of 
floral envelopes, as in the Goosefoot (jig. 29), it is customary 
with some botanists to call this the calyx, whether it is coloured 
or green ; it is so termed in this volume. Other botanists, 
however, under such circumstances, call the whorl that is 
present a perianth. Those, again, who use the term perianth 
in this sense also sometimes apply it, in all cases, to flowers 
whether of Monocotyledons or Dicotyledons, when the true 
floral envelopes are all coloured as in the Lily, or all green as 
in the Dock. The term is also sometimes employed in a general 
sense aS Synonymous with the floral envelopes. 
In their structure, venation, and characters generally, the 
sepals resemble the foliage leaves, and are covered like them with 
