THE STRUCTUEE OF PLANTS. 



9 



Flowers are developed from buds occupying the same position as those 

 which produce branches, and the botanist regards the flower as a short 

 branch with its leaves in a peculiar state of developement, the different 

 parts of the flower answering to leaves. The manner in which flowers 

 are arranged upon the stem is termed injiorescence. 



32. The simplest form is when the stem is terminated by a flower-bud, 

 as in the Tulip ; as the stem grows no longer in this direction, this is 

 called determinate inflorescence, but it is generally the case that flowers 

 are thrown out from the axils of the leaves, while the stem keeps on 

 growing. This form, of which there are several modifications, is inde- 

 terminate. If the flowers arise from the axils of the leaves of the stem 

 which remain like those of the rest of the plant, the inflorescence is axillary 

 (Fig. 184) ; but more commonly, when flowers are produced, the leaves 

 become smaller, and the joints of the stem shorter, and some kind of a 

 flower cluster is formed. In this case the reduced or transformed leaves 

 are called Bracts, and the flower cluster receives various names according 

 to the form it assumes. 



33. When flowers arise each from the axil of a bract upon a short 

 pedicel of its own, a Raceme is formed ; the main stem or axis is its 

 Rachis or Common Peduncle ; and the stalk of each flower, its Pedicel. 

 Here the lower flowers open first. If the flowers are sessile instead of 

 being raised upon pedicels, a Spike is produced. If the lower pedicels 

 of a short raceme are elongated so that all the flowers are raised up to 

 the same level, it forms a Corymb ; and if the internodes of the common 

 peduncle are at the same time shortened so that the pedicels all appa- 

 rently start from the same point, an Umbel (Fig, 108,) is the result, the 

 pedicels of which are called Rays, and the collected bracts at their base 

 form an Involucre. It is usually the case that the umbel becomes com- 

 pound and the rays themselves bear small umbels or Umbellets ; if these 

 have any involucres they are called Involucels. A Head is where the 

 flowers are closely crowded together as in the Clover (Fig. 74). In the 

 Composite Family, of which the common Sunflower is an example, the 

 apex of the stem is expanded to form a Receptacle, upon which the sepa- 

 rate flowers or Florets are placed ; here the bracts form an involucre 

 around the head and sometimes appear upon the receptacle as Chaff. A 

 fleshy spike like that of the Indian Turnip and Skunk Cabbage is called 

 a Spadix, and the hood-like involucre which sometimes surrounds it, a 

 Spathe. A scaly spike, like those of the willow, is called an Ament or' 

 Catkin. 



If the pedicels of a raceme are branched a Panicle is produced. 



In the determinate form of inflorescence, the flowering is often con- 

 tinued by the production of flowering branches from the axils of the 

 leaves or bracts below the terminal flower ; these branches may throw 

 out others, and thus a Cyme is produced. In this case the central or 

 uppermost flower is oldest and it is thus distinguished from forms of in- 

 determinate inflorescence. A flower-stalk which arises from below or 

 near the surface of the ground is called a Scape. 



34. The Flower has two kinds of organs ; the flower-leaves or Floral 



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