SECT. II 



PHANEROGAMIA 



451 



different modes of insertion of the ovary frequently occur ; thus a 

 flower may be slightly perigynous (many Leguminosae) or imperfectly 

 epigynous. 



The flower-axis can, in addition, by the formation of outgrowths of 



l ig. 383. — Different flowers belonging to the family Rosacea?, cut through longitudinally. 1, 

 Potentilla palustris, hypogynous ; 2, Alchemilla. alpina, perigynous ; 3, Pirns Mcdus, epigynous. 

 (After Focke in Nat. PJlanzen-familien, magnified.) 



different natures, essentially modify the structure of the flower. These 



accessory structures are sometimes large and corollaceous, as in 



Passiflwa (Fig. 489), but they are usually inconspicuous and confined to 



the DISC. The latter constitutes either a continuous ring or a circle of 



glands or scales, occupying generally a position 



between the andrcecium and gyncecium (Fig. 384). 



The disc usually secretes a sweetish fluid, and is 



then termed a nectary, in consequence of its 



biological function. Other parts of the flower, 



the petals for instance, may be developed as 



nectaries (Aconitum, Fig. 462). 



Arrangement and Number of the Floral 

 Leaves. — In some Angiosperms, as in most 

 Gymnosperms, the floral leaves are all or in part 

 arranged spirally. Flowers in which the spiral 

 arrangement of the leaves prevails, as, for ex- 

 ample, is generally the case in the Ranunoulaceae, 

 are termed acyclic. 



In a large majority of Angiosperms the flowers 

 are CYCLIC, and have their leaves arranged in whorls 

 five successive whorls are present, alternating regularly with each other. 

 Of these, two belong to the perianth, two to the andrcecium, and one 

 to the gyncecium. Flowers constructed after this type are described 

 as pentacyclic (Fig. 385). 



The number of parts in a whorl is usually the same in the 

 perianth and andrcecium — in Monocotyledons generally three, in 

 Dicotyledons five. This uniformity in the number of members in the 

 whorls may also extend to the gynoecium ; but, as a rule, particularly 



Fig. 384.— Flower of Vinus 

 vinifera. a, Calyx; b, 

 corolla ; c, disc-glands 

 between the stamens ; 

 d, e, gynoecium. (After 

 Berg and Schmidt, 

 magnified.) 



Most frequently 



