THE ORCHIDS OF NEW ENGLAND. 



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matter which envelopes the pollen-grains in. Cypripedium and 

 which can be drawn out into threads, we may suspect that in 

 this latter genus — the least differentiated in structure of all 

 the Orchidese — we see the primordial condition of the elastic 

 threads by which the pollen-grains are tied together in other 

 and more highly developed species. ... In some Neotteae, 

 especially in Goodyera, we see the caudicle in a nascent con- 

 dition projecting just beyond the pollen-mass, with the threads 

 only partially coherent. . . . In the Ophreae we have bet- 

 ter evidence than is offered by gradation, that their long, rigid 

 and naked caudicles have been developed, at least partially, by 

 the abortion of the greater number of the lower pollen-grains 

 and by the cohesion of the elastic threads by which these 

 grains were tied together. I had often observed a cloudy 

 appearance in the middle of the translucent caudicles in cer- 

 tain species ; and on carefully opening several caudicles of O. 

 pyramidalis, I found in their centres full)' half way down 

 between the packets of pollen and the viscid disc, many pollen- 

 grains (consisting as usual, of four united grains), lying quite 

 loose. These, from their embedded position, could never by any 

 possibility have been left on the stigma of a flower, and were 

 absolutely useless." He supposes that " the changes have not 

 always been perfectly effected, and that during and after the 

 many inherited stages of the abortion of the lower pollen- 

 grains, and of the cohesion of the elastic threads, there still ex- 

 isted a tendency to the production of a few grains where they 

 were originally developed ; and these were consequently left 

 entangled within the now united threads of the caudicle. . . . 

 The little clouds formed by the loose pollen-grains within the 

 caudicles of O. pyramidalis are good evidence that an early pro- 

 genitor of this plant had pollen-masses like those of Goodyera, 

 and that the grains slowly disappeared from the lower parts, 

 leaving the elastic threads naked and ready to cohere into a 

 true caudicle." 



