SECT. II 



PHANEROGAMIA 



713 



as is shown in the longitudinal section (Fig. 77S), a bud on its summit which 

 already shows a pair of scale leaves. This tuber has arisen as an axillary bud in 

 relation to one of the first scale-leaves of the plant, and with its tuberous, swollen, 

 first root has broken through the subtending scale-leaf (Fig. 782). It is destined 

 to replace the parent plant in the succeeding season. 



In considering the flower, the spiral torsion of the ovary, which brings the 

 labellum into the anterior position, must first be recognised. Tlie labellum is 



Fig. 780. — Orchis m'ditttris. A, Flower : «, 

 bract ; &, ovary ; c, the outer, and d, the 

 two anterior inner perigone leaves ; c, label- 

 lum with the spur/; g, gynostemiuni. l^, 

 Flower after removal of all of the perigone 

 leaves with exception of the upper part of 

 the labellum: h, stigma; I, rostellum ; V, 

 tooth-like prolongation of the rostellum ; 

 in, anther; //, connet-tive ; o, polUniuni ; q, 

 viscid disc ; p, staminodium. '', A poUin- 

 ium : )•, caudicle ; s, pollen. D, Ovary in 

 transverse section. (After Berg and 

 Schmidt.) 



G. 7S1. — Vanilla plauifoUa (reduced. After Berg 

 and Schmidt ; from Exgler and Prantl). A, 

 Labellum andgynostemium ; B, gynosteniium from 

 the side ; C, summit of the gynostemiuni from in 

 front ; D, anther ; E, seed, (^lagnified.) 



trijiartite and the larger middle segment is bifid at its free end. At the base of 

 the labellum a spur is formed by the bulging out of this segment of the perianth ; 

 this serves as the nectary and the opening leading into it is situated ju.st below the 

 gynostemiuni (Fig. 780, A, B). The latter bears on the side that is turned towards 

 the lower lip, and to an insect alighting on this, the large stigniatic surface (A) 

 corresijonding to two confluent stigniatic lobes. The third stigmatic lobe is trans- 

 formed into a structure termed the rostellum (/, /•) and stands in relation to the 

 male organ. The single fertile anther consists of two thecre joined together by the 

 connective which appears as the end of tlie gynostemiuni. The whole mass of 

 pollen of each of the two pollen-sacs is joined together by an interstitial substance 

 which continues below to form a stalk ; the whole structure, which has a waxy 

 consistence, is called a pollinium, and the stalk goes by the name of the caudicle. 



