POSITIVE DE DO II B L E M ENT . 



8] 



again the comparative method comes to the aid of those 

 sufficiently enlightened to be aware of its value in 

 solving such problems. 



We next must consider certain abnormal orchid- 

 flowers in this connection. As everyone is aware very 

 great and far-reaching changes, in which abortion and 

 excessive fusion and modification of various members 

 of the whorls has played a marked role, have occurred 

 during the evolution of the orchid -flower. As regards 

 the arrangement of its parts the ancestral flower must 

 have conformed to the Liliaceous type, with two 3- 

 merous whorls in the perianth and andrcecium, and 

 three carpels. The androecium is the whorl which has 



Fig. 93. — Butomus umbellatus (Flowering Rush). Diagram of flower 

 shown in Plate XXXVII, fig. 4. (After Celakovsky.) 



undergone most change. Of the outer whorl only one 

 fertile stamen remains, viz., the anterior one which 

 appears in the column ; the two lateral posterior ones 

 are only represented by ridges at the sides of the lip 

 with which they have become intimately fused. All 

 three stamens of the inner whorl are suppressed, having 

 apparently become wholly incorporated into the column 

 whose wing-like appendages perhaps represent traces 

 of them. 



In Gypripedium, however, the anterior lateral stamens 

 of the inner whorl are present and fertile, while, in 

 other genera, the fertile stamen of the outer whorl is 

 present, though sterile and in the form of a large 

 staminode. 



In some orchids, however, there are normally a 

 vol n. 6 



