244 HOMOLOGIES OP THE Chap. VIII. 



some doubt on the view that the labellum is always 

 an organ compounded of one petal and two petaloid 

 stamens ; for if any one were to assume that from some 

 unknown cause the lateral vessels of the lower petals 

 had diverged in an early progenitor of the Orchidean 

 order from their proper course into the antero-lateral 

 ovarian groups, and that this structure had been in- 

 herited by all existing Orchids, even by those with the 

 smallest and simplest labellums, I could answer only 

 as follows ; but the answer is, I think, satisfactory. 

 From the analogy of other monocotyledonous plants, 

 we might expect the hidden presence of fifteen organs 

 in the flowers of the Orchidea3, arranged alternately 

 in five whorls; and in these flowers we find fifteen 

 groups of vessels exactly thus arranged. Hence there 

 is a strong probability that the vessels, A2 and A3, 

 which enter the sides of the labellum, not in one or 

 two cases, but in all the Orchids seen by me, and which 

 occupy the precise position which they would have 

 occupied had they supplied two normal stamens, do 

 really represent modified and petaloid stamens, and 

 are not lateral vessels of the labellum which have 

 wandered from their proper course. In Habenaria and 

 Bonatea,* on the other hand, the vessels proceeding 



* In Bonatea speciosa, of which ments of the two upper petals 



I have examined only dry speoi- cohere with the labellum, causing 



mens sent me by Dr. Hooker, the it to have five segments, which is 



vessels from the sides of the upper a most unusual feet. The two 



sepal enter the postero-lateral wonderfully protuberant stigmas 



ovarian group, exactly as in also cohere to the upper surface of 



Habenaria. The two upper potala the labellum ; and the lower sepals 



are divided down to their bases, apparently also cohere to its under 



and the vessels supplying the side. Consequently a section of 



anterior segment and those supply- the base of the labellum divides 



ing the anterior portion of the one lower potal, two petaloid 



posterior segment unite and then anthers, portions of the two upper 



run, as in Habenaria, into the petals, and apparently of the two 



antero-lateral (and therefore lower sepals and the two stigmas : 



wrong) group. The anterior seg- altogether the section jiasscs 



