746 



BOTANY 



PART II 



as an alighting place for visiting insects, becomes anterior either by 

 the torsion of the whole flower through 180 (cf Figs. 828, 831) or 



by the flower being bent back- 

 wards. 



The Orchidaceae attain their 

 highest development in the tropics 

 where they form an important part 

 of the epiphytic vegetation. Orchis, 

 Ophrys, Gymnadetiia, Platanthera 

 with tubers ; Epipactis, Cephalan- 

 thera, Listera with branched 

 rhizomes ; Neottia, the Bird's-nest 

 Orchid, Epipogon, Coralliorrhiza, 

 Limodorum almost destitute of 

 chlorophyll. They live saprophyti- 

 cally or more correctly as parasites 



FIG. 827. Flower of Canna iridiflora. f, Ovary ; 

 k, calyx ; c, corolla ; I, labellum ; st^- s> the 

 other staminodia ; a, fertile stamen ; g, style. 

 ( nat. size.) 



FIG. 828. Orchidaceae. Floral 

 diagram (Orchis). (Modified after NOLL.) 



at the expense of their mycorrhiza ( 46 ). Cypripedium, Ladies' Slipper, with two 

 lateral fertile stamens of the inner whorl. 



Orchis militaris, which is represented in Fig. 833, will serve as an example for 



FIG. 829. Orchis militaris. Longitudinal 

 section passing through the old and new 

 tubers. (After LUERSSEN.) 



FIG. 830. Root-system of Orchis latifolia. b, 

 Base of stem ; s, scale leaf ; t', old, t", young 

 tubers ; fc, bud ; r, roots. (After H. 

 SCHENCK.) 



more detailed consideration. At the period of flowering a pair of fleshy tubers will 

 be found at the base of the plant, both of which are covered with root hairs. The 

 large or brown tuber of more spongy texture continues above into the stem which 



