58 Haynes: AYTONIA 
Plagiochasma elongatum Lindenb. & G., from Mexico, known 
to the writer only through descriptions, appears to resemble the 
Jamaican plant but the latter differs in possessing a shorter and 
broader frond which is 10-14 mm. long while that of P. elongatum 
reaches 35 mm.; P. elongatum has only 2~3 cells around pore, the 
Jamaican plant 4~5 cells; the ventral scales of Aytonia Evansti — 
taper gradually, while those of Plagiochasma elongatum are de- 
scribed by Stephani * as abruptly attenuate to the appendiculum. 
Aytonia jamaicensis sp. nov. 
Thallus light-green with a narrow purple margin, somewhat 
plane or broadly canaliculate, ovate to linear-oblong, 5-18 mm. 
x 5-6 mm., innovating from the apex and from the side of the 
costa ; margins of thallus elevated undulate-crenulate and slightly 
crisped ; width .of thallus in cross-section six times that of 
maximum height ; the epidermal cells generally quadrate, showing 
small trigones ; the stomata large, elevated, with 5-8 cells around 
the pore in 2-4 concentric series: ventral scales vinous-purple, 
strongly decurrent and approximate in the median ventral line, 
imbricated, broadly lunate or ovate, projecting beyond margin of 
thallus only at notched apex, reflexed over the growing point; 
appendicula ovate-lanceolate, occasionally geminate, strongly 
constricted, 7-12 cells in maximum width, with a_uniseriate 
apiculum of 1-3 cells in length, margins subentire, undulate- 
crenate or sparingly toothed : oil-bodies completely filling isolated 
cells in the colorless stratum of thallus : monoicous: 9 receptacles 
usually several in a series on an apical innovation in front of 
androecium: scales of androecium deltoid or cuneate-ovate: 
peduncle 11-16 mm. long: carpocephalum 2—4-lobed, generally 
maturing two opposite sporogonia and then concave or transversely 
furrowed above or sometimes slightly convex ; scales of the car- 
pocephalum lanceolate or linear-lanceolate, 5-14 cells in greatest 
width, often acuminate with a constriction near the apex: spores 
averaging 85 4, yellow or brownish, enveloped in a very loose 
reticulate-rugose exospore, this easily detachable, spore after 
removal of exospore averaging 46: elaters 2-3-spiral, occasion- 
ally forked, somewhat attenuate at ends, 2 55-374 long, 84 in 
maximum width. (PLATE 6.) 
The above description has been drawn from material collected | 
at Chestervale, Jamaica, February, 1903, L. W. Underwood 1173 
(type) and 7777 [both mixed with Redoulia hemisphaerica]. 
* FRANZ STEPHANI. Species Hepaticarum. Bulletin de Herbier Boissier 6: 
785. 1898. 
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