THE STRUCTURE OF THE FLOWER 327 



calyx. This produces the calyx cup, which is very well seen in 

 the Rose. The gynaeceum is enclosed in the calyx cup, or, as 

 it is sometimes called, the receptacular cup, and the stamens, 

 petals, and free parts of the sepals arise from the edge of it. 

 This kind of flower is called perigynous, while the simpler type, 

 in which the receptacle is more or less conical, is called 

 hypogynous (cf. Buttercup, Text-fig. XXVI.). 



As a further development, the gynaeceum may fuse 

 completely with the calyx tube, so that all the floral parts 

 appear to grow on the top of the ovary (cf. Crocus, Text- 

 fig. XXX., and Groundsel, Text-fig. XXIX). The flower is 

 then said to be epigynous^ and the ovary inferior. 



Besides the floral parts which we have mentioned, special 

 structures called nectaries occur in some flowers. These take 

 various forms, but agree in one essential feature namely, that 

 they secrete honey. In many flowers the nectaries are modified 

 stamens, as in the Globe-flower (p. 207), where they are horn- 

 shaped structures. In this case the modified stamen both secretes 

 the honey, and forms a receptacle to hold it. In the Pansy, on the 

 other hand (Text-fig. XV.), processes from two of the stamens 

 secrete the honey, which drops into a spur-like receptacle, 

 hollowed out of the base of the front petal. In the Lesser 

 Butterfly Orchid (Text-fig. XI., 1), one of the perianth members 

 is spurred like the Pansy ; but here it is the tissue of the spur 

 itself which secretes the honey. In the Buttercup (Text -fig. 

 XXVI., 2), honey oozes out from a patch of glandular tissue 

 concealed behind a little scale at the base of the petal. 



Starting from such a flower as the Buttercup, there seem to 

 be several lines along which evolution may proceed. One of 

 the most important steps involves the union of the petals that 

 is to say, polypetaly is replaced by gamopetaly. On the other 

 hand, the plant, instead of becoming more highly evolved in 

 regard to the corolla, which aims at the attraction of insects, 

 may decide to dispense with it altogether, or to reduce it to 



