ANGIOSPERMS. 



547 



mature, the filaments appear as if they sprang from the inside of the perianth ; 

 the earhest stages of development show, however, that the perianth-leaves and the 

 stamens spring in succession and separately from the receptacle ; it is not till a later 

 period that intercalary growth begins at the part of the receptacle from which both 

 spring ; in this manner a lamella grows up which structurally forms the basal portion 

 of the perianth-leaf, and which at the same time bears the stamen, so that the 

 appearance is presented as if the stamen sprang from the centre of its inner surface. 

 This is shown in Fig. 370, ^, where /> is a perianth-leaf and a an anther sessile upon 

 it ; the two stand at first distinct on the young receptacle one over the other ; the 

 portion of leaf lying beneath a and p is not formed till a much later period by 

 intercalary growth, and pushes up at the same time the true perianth-leaf ^ and 

 the stamen a. This kind of adhesion is especially frequent in those flowers whose 

 petals have also become coherent laterally into a tube, such as Compositse, Labiatae, 

 Valerianacese, &c. On the other hand, the stamen may also become adherent 

 in various ways to the gynaeceum. In Sterculia Balanghas (Fig. 371) this structure 



Fig. 370. — VXawe^x o{ Manolesia glabraia ; 4 before open- 

 inff ; B open ; C the gyneeceum, gp the gynophore ; D hori- 

 zontal section of the ovary ; E fruit ripening on its pedicel. 



Fig. 371. — Flower oi Sterculia Balanghas; 

 A, gs the gynophore, y ovary, n stigma ; B hori- 

 zontal section of the ovary. 



is only apparent, depending simply on the small stamens, which are placed close 

 beneath the ovary, becoming raised up together with it by the elongation of a 

 part of the receptacle ; from their small size they appear like a mere appendage of 

 the large ovary ; the part which bears both the organs, the Gynophore^ is therefore 

 in this case an internode of the floral axis. Much more complicated is the history 

 of the formation of the true Gynostemium (column) which is formed above an 

 inferior ovary, as in the Aristolochiaceae, and especially in the Orchideae, where 

 these adhesions and displacements of the parts of the flower are also combined with 

 abortion of certain members. Since these relationships will be explained in the 

 sequel, the examination of Fig. 372 will suffice for the present, where the flower of 

 Cypripedium is represented from the side (^), from behind (-5), and from front (C), 

 after removal of the perianth {pp). f is the inferior ovary, gs the gynostemium, 

 resulting from the adhesion of three stamens — two of which {ad) are fertile, while the 

 third (.9) forms a sterile staminode — with the carpel, the anterior part of which bears 

 the stigma {n). In this case the gynostemium consists entirely of coherent foliar 

 structures, or of the basal portions of the staminal and carpellary leaves, both of 



N n 2 



