66 ROTANY FOR BEGINNERS. [Ch. XL. 
264. Involucrum. This term is derived from the Latin, in- 
volvo, to wrap up; this kind of calyx is usually found at the 
base of an umbel, as in the Carrot. It is said to be universal, 
when it belongs equally to the whole of an aggregate flower ; 
and partial when it encloses one floret, which, with others, con- 
stitutes a compound or aggregate flower. The term involucrum 
is also applied to the membranous covering in the fructification 
of ferns. 
265. Ament, or catkin, is a kind of calyx, by some classed as 
a mode of inflorescence; it consists of many chaffy scales, 
ranged along a thread-like stalk or receptacle; each scale pro- 
tects one or more of the stamens or pistils, the whole forming 
one aggregate flower. The Ament is common in forest trees ; 
as in the Oak and Chestnut, and is also found in the Willow 
and Poplar. In some trees the staminate flowers are enclosed 
in an ament, and the pistillate in a perianth. 
266. Spatha signifies a sheath. It is that kind of calyx 
which first encloses the flower, and when it expands, bursts 
lengthwise, and often appears at some distance below it. The 
Wild-turnip, or arum, furnishes an example of this kind of ca- 
lyx, enclosing a kind of inflorescence called a spadix. From 
the peculiar appearance of the spadix, as it stands up sur- 
rounded by the spatha, it is sometimes called Jack in the pul- 
pit. (See Fig. 41, a.) The spatha is common in many of our 
Fig. 41. cultivated exotics, as in the 
Daffodil, where it appears 
brownish and withered af- 
ter the full expansion of the 
flower.— You see here a re- 
presentation, (Fig. 41, 5), 
of the spatha of the Arum, 
and of the Narcissus (c).. 
In the Egyptian Lily, th 
spatha is white and per 
nent, and the stamens an: 
pistils grow separately up- 
on the spadix. Palms havea 
spadix which is branched, 
and often bears a great 
quantity of fruit. 
264. What is an involucrum 2? 
265. What is an ament ? 
266. What isa 
