— 62 — 
mens from Hudson’s Bay are referable to Z. rupestris. They were so 
named by Mitten who had a portion of the type. Our Virginia specimens 
agree with Z. viridissimus in habitat as well as structure, It will be found 
that European authors do not agree as to the specific rank or generic position 
of these two species nor as to the presence or absence of propagulae in Z, 
conoideus . Limpricht and Brotherus say they are absent, but Correns 
figures them for this (Fig. 73) species!- Also it will be found that Limpricht, 
Dixon and Paris Index place Z. rupestris as a variety of Z. viridissimus 
whereas Brotherus follows Lindberg and maintains it as a distinct species. 
We have adopted the latter opinion, not only because our collections are 
being arranged according to the Engler and Prantl Pflanzenfamilien Synop- 
sis, but also because of the great difference in habitat and range of these 
two species, as well as other differences in aspect and structure, Z. rupes- 
tris being a shorter plant, reproducing by numerous propagulse. 
Zygodon Sullivantii has never been found in fruit and its family and 
genus have always been doubtful. Sullivant first described it as Syrrho- 
podon? excelsus' Muller renamed it as Zygodon Sullivantii and the manual 
has it under Amphoridium. Mitten placed it in his herbarium under Lepto. 
dontium and recent studies have led me to believe that this is its nearest 
alliance. Its method of propagation by leaves rooting at apex and small 
deciduous terminal buds and lateral branchlets is well illustrated by Sulli- 
vant. It will ..also be found that Brotherus places Zygodon Sullivantii in 
the group having a double peristome with Z. gracilis; its generic position 
must necessarily remain uncertain until the fruit is found! It will be noted 
that De Notaris also placed Zygodon gracilis in Leptodontium. Even the 
genus Leptodontium is variously placed, Mitten including it in the Dicran- 
aceae and Brotherus in the Pottiaceae! 
The following synopsis and descriptions may be of service to those who 
have not access to the literature cited above: 
SYNOPSIS. 
Peristome lacking. Tomentum with propagulse. 
Leaves lanceolate, apiculate, on trees. 1. Z. viridissimus . 
Leaves ligulate, lanceolate, on rocks. 2. Z. rupestris . 
Peristome double. Tomentum without propagulse. 
Leaves entire. In loose small tufts on trees. (European — Z. conoideus .) 
Leaves serrate. On limestone rocks, usually sterile. 3. Z. gracilis . 
ZYGODON Hook, and Tayl. Muse. Brit. 123. 1S18. 
Plants pulvinate, light or dark green, on rocks or trees. Stems erect, 
tomentose with rufous tomentum, branched. Leaves crowded, appressed, 
secund or twisted when dry, spreading or recurved when moist, lanceolate or 
linear-lanceolate, apiculate or blunt, entire or serrate at apex ; costate nearly 
to apex, rarely excurrent; cells round, incrassate, smooth or papillose, 
elongated at base. Dioicous or autoicous rarely heteroicous or polyoicous, 
often, sterile and reproducing by septate propagulae. Perichaetial leaves 
only slightly different. Seta exserted. slender. Capsule erect, pyriform or 
