POSITIVE DEDOUBLEMENT. 



63 



0. Lawrencianum ; the present writer has seen the 

 phenomenon in G. insigne, but in this case the two 

 sepals were not quite free at the base. 



Heinricher mentions that in a lady's slipper (G. 

 Galceolus) these sepals were fused only at the base. 

 It is also very interesting to note that Irmisch found 

 that in the development of this species the two sepals 

 are at first separate, and only at a later stage become 

 united. 



Heinricher states that in the Canadian G. arietinum 

 they are normally quite free. This has been confirmed 



o o 



a b c 



Fig. 83. — a, Nymph&a alba (White Water Lily). Quinquesepalous 

 flower, b, Normal flower of the same, c, Nnphar luteum (Yellow 

 Water Lily). Normal flower for comparison with those of Nymphsea. 

 b, bract. (Diagrams, after Celakovsky.) 



from herbarium-specimens at Kew. These cases must 

 be regarded as reversions to the primitive 3-merous 

 condition of the calyx. The single posterior sepal has, 

 of course, originally arisen by fusion of the two lateral 

 ones which are always present in other orchids. A 

 drawing by Mr. Gr. S. Saunders has also been seen 

 showing complete fission of the anterior sepal. 



In the white water-lily (Nj/mphsua) the calyx (in- 

 cluding for the time being the transposed bract) con- 

 sists of four orthogonally-arranged sepals (fig. 83 b), 

 whereas in the yellow water-lily (Nuphar) there 

 are five, of which sepals 3 and 5 are in the lateral 

 posterior position (fig. 83 c). Celakovsky observed 



