204 



readily discernible on the surface of the embryo capsule (fig. lo) 

 make, in the judgment of the writer, the induction that the de- 

 hiscence is spiral so safe and certain that he has felt no hesitation 

 in so describing it and in basing the generic name upon this char- 

 acter. The absence of thickenings in the walls of the 

 cells of the capsule valves is noteworthy. Schififner states* of 

 all the Ju7igermaitiaceae akrogynae : " Die reife Kapsel besitzt 

 eine aus 2 bis mehr Zellschichten bestehende Wand, deren Innen- 

 schicht in ihren Zellen stets Verdickungsleisten enthalt." In 

 Gyrothyra, the transverse walls of these cells usually appear a 

 trifle thicker than the longitudinal, but the walls are otherwise 

 wholly without traces of local thickening. 



In respect to structure of the sporogonial envelopes, Gyrothyra 

 is one of several very interesting transitions from the ordinary Jun- 

 germania type to the various pouch-bearing genera. Considered 

 from this point of view and from certain other gametophytic 

 characters, its nearest affinities are undoubtedly to be found in 

 that section of Nardia represented by Nardia Jiaeniatosticta (Nees) 

 Lindb., of Europe. In manner of dehiscence of capsule it recalls 

 the marsupiiferous genus Kantia; but the valves of Gyrothyra are 

 much longer and their cell-walls lack the local thickening, while, 

 of course, no generic comparison of the two can be made so far 

 as the gametophyte is concerned. 



It is with pleasure that the author associates with this novel 

 plant the name of one who, by his numerous papers upon the 

 American Hepaticae, as well as by his unfailing generosity, has 

 placed the younger workers in the same field under lasting obli- 

 gations. It should be noted that, although Professor Macoun's 

 specimens were without the capsules, which reveal the distinctive 

 generic character of Gyrothyra, Professor Underwood had already 

 recognized that they represented something undescribed. 



E^xplanation of Plates 302, 303. 



1. Entire 9 plant. X 5- 



2. Cauline leaves. X '8' 



3. Marginal and adjacent leaf-cells. X 225. 



4. Transverse section through marginal portion of leaf. X 216. 



5. Underleaves. X 24. 



*Engler and Prantl, Nat. Pfl. Fam. i : Abt. 3, 71. 



