ORCHIDACEyE 



vertical rhizome, root-shoots (of. Plate 104) extend widely in a 

 nearly horizontal plane and eventually produce new plants. It 

 will be understood at once that in multiplication by means of 

 root-shoots Pogonia ophioglossoides is fundamentally different 

 from Triphora trianthophora which multiplies by means of true 

 stolons that terminate in tubers. 



The secondary stems of P. ophioglossoides are usually described 

 as monophyllous, although the bract subtending the flower may 

 be foliaceous and properly regarded as a second leaf. If two or 

 more flowers are produced, an occurrence which is not at all rare 

 in the Southern States, each flower is subtended by a bract. 



The flower differs from that of Triphora trianthophora in du- 

 ration and may remain in perfection for several days. At the base 

 of the labellum there are two glands or calli, structures which are 

 present in the tropical species of Cleistes and in Isotiia verticil- 

 lata and /. qffinis. (Cf. Plates 104, 105 and 107.) These glands, 

 as has already been stated, are wanting in Triphora which has a 

 very different lip-base, and their absence is still another indica- 

 tion of generic differentiation between this genus and Pogonia. 

 The column terminates in a deep clinandrium or excavation, and 

 the anther is hinged in such a way that it is mobile and when in 

 normal position hangs with the pollen cells looking at the floor of 

 the clinandrium, not outward as in Triphora and Psilochilus. The 

 margin of the clinandrium is toothed. In the structure of the an- 

 ther, we find one of the most salient generic characters on which 

 to rely in removing Pogonia from Triphora. The pollen of Po- 

 gonia, as is shown in the illustration (Plate 104), differs funda- 

 mentally from the pollen of Cleistes and Isotria. The grains con- 

 sist of single cells held together by some viscid substance. I have 

 been very much impressed by the constancy of this character in 



all of the material I have examined, taken from the extremes of 



[15] 



