INTRODUCTION TO BRITISH BOTANY ix 



of the heads of flowers. When they grow in this form they are 

 termed an involucre (from involvo, to wrap up, because they enclose 

 the flowers before expansion). 



The Flower. — This, as it is the most ornamental, so it is the 

 most important part of the plant, being rarely produced until the 

 juices fit for its nourishment have been selected by the roots and 

 matured by the leaves, and containing all the apparatus necessary 

 for perfecting seeds. In flowering plants, besides the parts which 

 are indispensable to the ripening of seeds, there are others which 

 evidently serve as a protection, and others, again, the use of which 

 is not known. The flower, however, generally being essential to 

 the continuance of the species, has been selected as the part on 

 which to found every arrangement of plants which can lay claim 

 to accuracy or utility. A thorough knowledge of its structure is 

 therefore necessary, before the student can proceed to discover the 

 names of the commonest plants which are: flung with so bountiful 

 a hand over our hills and fields. 



The Calyx. — This name is given to that 'part of the flower which 

 in the bud stage is outside all the rest, and which when the flower 

 is expandecl encircles the more delicate parts. It is usually green, 

 and consists of several leaves, termed sepals ; but these sepals are 

 often united at the base and form a cup, (hence the name calyx, 

 a cup). 



It is unnecessary here to describe the various forms of the calyx, 

 which are very numerous. It may be remarked, however, that 

 when the calyx is divided into two distinct lobes, one of which over- 

 hangs the other, it is termed gaping ; in- the Mallow Tribe it is 

 double ; and in Compound Flowers, the Valerian and Teazel Tribes, 

 it is at first a mere ring, but afterwards becomes a chaffy or feathery 

 appendage to the seed, termed a pappus. 



The Corolla. — Within the calyx is the corolla (little crown), a 

 ring of delicate leaves called petals, usually coloured — that is, not 



g;reen — and often fragrant. The petals are either distinct, as in 

 the Rose, in which the expanded part is termed the limb, the lower 

 the claw ; or*united below, when the expanded part is termed the 

 border, the lower the tube. The corolla more frequently has as 

 many petals or divisions as there are sepals ; and if these are all 

 of the same size and shape, the corolla is said to be regular. 



