BKACTS. 67 



Bracts. 



110. There are often to be found organs situated between 



the true leaves and the calyx, varying from them in outline, 

 color, and size, which are called bracts. Many varieties of 

 bracts have been, till very recently, classed as varieties of the 

 calyx ; and some botanists, even at the present day, adopt this 

 arrangement. The bract seems to occupy a space between the 

 leaf and calyx, not only by collocation on the plant, but in 

 constitution and functions. They appear to pei'form the same 

 office in many cases as the calyx, and in others seem not to 

 dift'er from the true leaves. 



111. Their position and form have given them various 

 names, of which the following are the most common : 



When they appear as simple scales on the peduncle, or at 

 its base, they take only the general term bract, as in the 

 Heart's-ease and Veronica agrestis. 



When they are verticillate and surround several flowers, they 

 constitute an involucre, as in the UmhelUferoB. In Co?npositce, 

 the involucre assumes the appearance of a calyx, inclosmg many 

 flowers, but each floret has a calyx more or less developed, 

 inclosing the seed and appearing on its summit in the form 

 of egret, scales, paiyinis, or an elevated margin. At the base of 

 this involucre there are often bracts, not constituting a part of 

 it. These are called bractleis, and the involucre is said to be 

 bracteolate. In the Cupuliferce, the involucre assumes a more 

 singular appearance, forming in the Oaks the hard cup-shaped 

 organ indorsing the base of the acorn, and in the Chestnut con- 

 stituting what is well known by the name of bur. The real 

 calyx, in these cases, exists in a rudimentary form imme- 

 diately surrounding the pistils, as may be readily observed in 

 the pistillate flower of the Chestnut. In the Cornus or Dog- 

 wood, the involucre consists of the four large, white, showy 

 leaves which one, not a botanist, would take for the corolla. 

 In the Euphorbia, the involucre is composed of two rows of 

 united leaves, forming what might be easily mistaken for a 

 calyx and corolla, as the outer part is green, while the inner is 

 colored. In the Beech it resembles a pericarp. 



The bracts of the Calkin are usually called squamce or scales — 

 a term usually applied to any scaly a[)pearance ; and the organ 

 on which such scales appear is said to he squamose. 



110. What are bracts ?— 111. When called an involucre ? How in Com 

 positse ? In Cupuliferae '^ Chestnut? Cornus? Euphorbia? Beech 'J 



