ORCHIDACE^ 



gard P. triajithophora as a representative of a very well defined 

 group of which Triphora gentianoides {Sw.) Ames 8^ Schltr. 

 comb. nov. {Arethusa gentianoides Sw. Fl. Ind. Occ. 3 (1806) 

 1436), may be taken as an example. 



Cleistes has been looked on as a group referable to Pogonia. 

 As a subgenus it is represented in our range by Pogonia divari- 

 cata. If it should be deemed wise, as I believe it is, to treat P. 

 ophioglossoides and its close allies in Asia as members of a distinct 

 genus readily characterized by simple pollen grains, then P. di- 

 varicata and the neotropical species to which it is related would 

 constitute the genus Cleistes. Under such circumstances P. ver- 

 ticillata and P. affinis of the Manual should be segregated as mem- 

 bers of a distinct group and transferred to Isotria, the most con- 

 spicuous character on which to base segregation being the verti- 

 cillate leaves and their behavior in vernation. (Cf. Plate 105, 

 fig. 9.) 



Just how much reliance to place on the character of the pollen 

 grains is, of course, a debatable question. It would seem that the 

 tendency of the pollen tetrads to break down early as in Cypri- 

 pedium, Cephalanthera and a few other orchid genera ought to 

 be taken as a fundamental characteristic in the contemplation 

 of generic differences. In Pogonia ophioglossoides the pollen te- 

 trads disintegrate into simple grains comparatively early in the 

 development of the flower; in fact, they may be found thoroughly 

 separated in buds that are still green. We find the same condi- 

 tion in the Asiatic P. japonica Reichb. f. H. G. Reichenbach in 

 his elaborate treatise on the structure of the pollen of the Orchi- 

 daceae figured the pollen grains of P. ophioglossoides as simple 

 at flowering time, not compound.^ In P. ophioglossoides var. hra- 

 chypogon Fernald and in P. japonica var. minor JMak., the pollen 



*D« Pollinis Orchidacearum Genesi ac Structura (1852). 



[5] 



