550 



BOTANY 



FlG. 555. Or'-! (J nat. si/e.) 



which terminates in tin- pyra- 

 midal inflorescence ; this axis 

 is surrounded at the base liy ;i 

 pair of scale - leaves and the 

 sheaths of the 2-4 elongated, 

 elliptical foliage leaves. The 

 smaller tuber is of tinner con- 

 sistence and of a white colour : 

 it bear.-., as is shown ill the 

 longitudinal section (Fig. 551), 

 a lnid 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-leave-. 

 of the plant, and with its 

 tuberous, swollen, first root has 

 lirnken through the subtend- 

 ing scale-leaf (Fig. 555). It 

 is destined to replace the 

 parent plant in the succeeding 

 season. The anatomical and 

 morphological differences be 

 tween the tuber and the ordi- 

 nary roots of the plant may be 

 explained by the consideration 

 that the tuber arises from 

 several coherent roots. The 

 existence in other species ; 1 _ 

 552) of palmately branched 

 tuliersincrcases the probability 

 of this explanation. 



In considering the flower, 

 the spiral torsion of the ovary, 

 which brings the lahellnm into 

 the anterior position, must first 

 be recognised. The label him 

 is tripartite and the larger 

 middle segment is bifid at its 

 five end. At the base of the 

 labellum a spur is formed by 

 the bulging out of this seg- 

 ment of the perianth ; this 

 serves as the nectary, and the 

 opening leading into it is situ- 

 ated just below the gyno- 

 stemium (Fig. 55:5 A, /?). 

 The latter bears on the side 

 that is turned towards tin- 

 lower lip, and to an insect 

 alighting on this, the large 



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