238 HOMOLOGIES OF THE Chap. VIIL 



scences on the labellum ; but I find the corresponding 

 vessels invariably present in the labellum of every 

 Orchid examined, — even when the labellum is very 

 narrow or quite simple, as in Malaxis, Herminium, 

 or Habenaria. 



We thus see that an Orchid-flower consists of five 

 simple parts, namely, three sepals and two petals; 

 and of two compounded parts, namely, the column and 

 labellum. The column is formed of three pistils, and 

 generally of four stamens, all completely confluent. 

 The labellum is formed of one petal with two petaloid 

 stamens of the outer whorl, likewise completely con- 

 fluent. I may remark, as making this fact more 

 probable, that in the allied Marantacese the stamens, 

 even the fertile stamens, are often petaloid, and 

 partially cohere. This view of the nature of the label- 

 lum explains its large size, its frequently tripartite 

 form, and especially the manner of its coherence to the 

 column, unlike that of the other petals.* As rudi- 

 mentary organs vary much, we can thus perhaps 

 understand the variability, which as Dr. Hooker informs 

 me is characteristic of the excrescences on the labellum. 

 In some Orchids which have a spur-like nectary, the 

 two sides are apparently formed by the two modified 

 stamens-; thus in Gymnadenia conopsea (but not in 

 OreJiis pyramidalis), the vessels, proceeding from the 

 two antero-lateral ovarian groups, run down the sides 

 of the nectary ; those from the single anterior group 

 run down the exact middle of the nectary, then 

 returning up the opposite side form the mid-rib of the 

 labellum. The sides of the nectary being thus formed of 

 two distinct organs, apparently explains the tendency. 



* Link remarks on the mtancr theonlumninhis"Benierkiingen" 

 of cohiiencc of the labellum to in 'Bot. Zeitung,' 1840, p. 745, 



