HOMOLOGIES OF ORCHID FLOWERS. 



35 



This view of the theoretical ty[)e of an orcliid tiower was accepted 

 hy Dr. Lindley and adopted by Mr. ])arwiu after further investigation. 

 Both Dr. Brown and ^fr. Darwin relied chiefly on the course of the 

 flbro-vascular bundles, spii'al vessels as they were then sometimes called 

 while in a rudimentary state. Mr. Darwin traced these upwards from 

 the ovary through the parts of the flower ; the result of his dissection 

 is given in the diagram below. The fifteen little circles represent 

 so many groups of filjro-vasculai bundles (si)iral vessels) in every case 

 traced down to the six large ovarium groups ; they alternate in five 

 Avhorls, and in order to guide the eye, the three central groups running 

 to the three instils are connected liy a triangle. The explanation of 



UPPEK SEPAL 



LABELLUM 



these fifteen groups given liy Mr. Darwin is that an orchid flower consists 

 of fifteen organs in a much ULodified and confluent condition ; the three 

 sepals and petals are simple organs, but tlif labellum and column are 

 compound; the labellum is formed of one petal and two petaloid stamens 

 of the outer whorl completely confluent (sec, infra). The column is 

 formed of three pistils and generally of four stamens all completely 

 confluent ; of the three i)istils, the two lower ones arc coalescent 

 and tlie upper one is modified into the rostelluin : llic six stamens 

 arr ill two whorls of three cacli, oi which one aluuc of thi' outer 

 whorl indicated liy A 1 in the diagram is fertile; but in Cypripedium 

 and Apostasia twn si aniens (if tlie inner whorl a\ and a2 are fertile, 

 while in Xeuwiedia and the anomalous Cypripedium caudatum Lindenii 



