DIV. II 



ANGIOSPERMAE 



747 



terminates in the pyramidal inflorescence ; this stem is surrounded at the base 

 by a pair of scale leaves and the sheaths of the 2-4 elongated, elliptical foliage 

 leaves. The smaller tuber is of firmer consistence and of a white colour ; it bears, 

 as is shown in the longitudinal section (Fig. 829), 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. 829). It is destined 

 to replace the parent plant in the succeeding season. 



C 



FIG. 831. Orchis militaris. A, Flower: a, 

 bract ; b, ovary ; c, the outer, and d, the two 

 anterior inner perigone leaves ; e, label- 

 lum with the spur/; g, gynostemium. B, 

 Flower after removal of all of the perigone 

 leaves with exception of the upper part of 

 thelabellum: h, stigma ; I, rostellnm ; /,-, 

 tooth-like prolongation of the rostellum ; 

 m, anther ; n, connective ; o, pollinium ; q, 

 viscid disc ; p, staminodium. C, A pollin- 

 ium : r, caudicle ; s, pollen. D, Fruit in 

 transverse section. (After BERG and 

 SCHMIDT.) 



Fio. 832. Vanilla planifolia, (reduced. After BERG 

 and SCHMIDT ; from ENGLER and PRANTL). A, 

 Labellum and gynostemium. B, Gynostemium 

 from the side. C, Summit of the gynostemium from 

 in front. D, Anther. E, Seed. (Magnified.) 



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

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

 tripartite 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 just below the 

 gynostemium (Fig. 831 A, E}. The latter bears on the side that is turned towards 

 the lower lip, and to an insect alighting on this, the large stigmatic surface (h) 

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

 formed into a structure termed the rostellum (I, k) and stands in relation to the 

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

 connective which appears as the end of the gynostemium. The whole mass of 



