REPRODUCTION— THE FLOWER. 



51 



form of the corolla may be strictly regular, as in 

 a Primrose; or irregular, as in a Snapdragon. 

 This irregularity is connected with the visits 

 of insects to obtain honey or pollen and, as a 



Fig. 61.— Forms of Corolla. 



Cruciate, b, Caryophyllaceous. c, Papilionaceous, d, Tubular, e, Campanulate. 

 f, Funnel-shaped, g, Rotate, h, Ligulate. i, Labiate, j, Personate, k, Personate 

 and spurred, l, Nectaries. 



consequence, to transfer the pollen to some 

 other flower. The colour and fragrance of the 

 corolla offer obvious attractions to insects. The 

 various forms which the corolla may assume are 

 very numerous. We can here only indicate the 

 general principle 

 of their construc- 

 tion, and leave the 

 details to be sought 

 for in botanical 

 text-books (fig. 61). 

 A compound flower 

 is one which con- 

 sists of a growth 

 of flowers or florets 

 closely crowded in 

 heads within an 

 involucre of bracts, 

 as in the Dande- 

 lion (fig. 62). 



Generally it is 

 easy to discrimi- 

 nate between the 

 calyx and corolla 

 by their position alone, but there are a few 

 cases where it is difficult to do so, and there 

 are cases where the calyx is brightly coloured, 

 as in Daphne Mezereon or where calyx and corolla 

 are alike in colour, as in Lilies, Tulips, &c. In 



Inflorescence of Dandelion. 



such cases the term perianth is used instead of 

 calyx or corolla. 



4. The Stamens. — Within the corolla are the 

 stamens, collectively constituting the andrcecium. 



A stamen usually consists of a "fila- 

 ment" or stalk, which supports a case 

 containing yellow dust; this case is a 

 sporangium called the anther, and the 

 yellow dust is made up of separate cells 

 generally called "pollen-grains", but 

 now known to be the equivalents of 

 the microspores of the lower plants, 

 and which are very varied in shape in 

 different plants (fig. 63). The pollen- 

 grains escape from the anthers either 

 by longitudinal chinks in the side, or 

 through pores at the top as in Heaths. 

 The stamens vary in number, position, 

 length, and form. The most impor- 

 tant differences are those concerning 

 their relative position. They are free 

 or distinct from any other parts, as 

 in the Poppy; or they may be in 

 union with the calyx, episepalous, or 

 with the corolla, epipetalous. When 

 quite free from one another and from 

 other parts they are hypogynous, as in 

 the Vine; when they are partly separate only 

 from the calyx they are perigynous; whilst in 

 some cases they remain so closely blended with 

 the tube of the corolla or the tube of the calyx, 

 and that in its turn is so joined to the ovary 

 that the stamens appear to come from its top, 

 when the term epigynous is applied, as in the 

 Carrot and other Umbelliferse. Plants having 

 free hypogynous stamens are called thalami- 

 floral; where they are partially inseparate from 

 the calyx they are called calycifloral ; when par- 

 tially inseparate from the corolla, cor ollifl oral ; 

 when partially inseparate from the ovary, 

 epigynous ; or when completely blended with the 

 upper part of the ovary and styles, gynandrous, 

 as in the Orchid family. 



The varied form and arrangement of the 

 stamens have generally a direct relation to the 

 protection of the pollen from injurious agencies ; 

 sometimes to its effectual dispersal and removal 

 to another flower — cross-fertilization; whilst at 

 other times the arrangements are such as to 

 facilitate the access of the pollen to the stigma 

 of the same flower, and so bring about close- 

 fertilization (fig. 64). For other details relating 

 to the stamens reference should be made to the 

 ordinary text-books. 



5. The Pistil. — The centre of a complete 

 flower is occupied by the pistil, which consists 



