ORCHIDACEtE 



distribution. Furthermore I have observed that the tendency of 

 the pollen of Pogonia to germinate in situ is very common, and 

 pollen grains that have germinated within the anther may be ob- 

 served even in dried material, when the grains are often in masses 

 held together by pollen tubes. I have observed this phenomenon 

 in Asiatic species as well as in our own P. ophioglossoides. 



There is still another difference in addition to those described 

 that serves to indicate generic distinction between Pogonia and 

 Triphora ; I refer to the behavior of the perianth after anthesis. 

 In Pogonia, Isotria and Cleistes the perianth falls away shortly 

 after the flowering season and is wanting at the time of dehis- 

 cence of the capsule. In Triphora the perianth persists and may 

 often be found on fruiting specimens at the time dehiscence takes 

 place. 



Canada to Florida westward to Minnesota. 



ISOTRIA Raf. 



Isotria verticillata {Willd.) Raf. in Med. Repos. N. Y. 5 

 (1808) 357. Helleborine affinis, Planta Mariana, Herbae Para- 

 dis facie quinquefoliata. P/2^A:.Mant. (1700) 101, t. 348. Arethusa 

 verticillata Willd. Sp. PI. 4 (1805) 81. Odonectis verticillata Raf. 

 in Med. Repos. 5 (1808)357. Pogonia verticillata Nutt. Gen. 2 

 (1818) 192. Arethusa medeoloides Pursh Flora 2 (1814) 591. Iso- 

 tria medeoloides i?a/: Fl. Tellur. 4 (1838) 47. 



\i Isotria verticillata is studied in the field in late April or early 



May, it will be observed that the flower-bud is just pushing 



through the protective covering formed by a verticil of closely 



imbricating leaves. (Cf. Plate 105, fig. 9. ) The leaves at this stage 



of development closely resemble imbricating bracts and present 



a condition found in no other species, /. affinis excepted, of the 



Pogonia complex. 



[16] 



