1918] JACKSON—PUCCINIA 307 
seated, arising from below the palisade layer, pulverulent, light 
yellow fading to whitish; urediniospores ellipsoid or obovoid, 
18-20 by 24-28 yu, wall pale yellow or colorless, thin, 1-1. 5 y, finely 
and moderately echinulate, pores obscure, apparently 2 equatorial: 
III. Telia epiphyllous, densely gregarious and often confluent 
on irregular spots, 0. 5—1. 5 mm. across, becoming scattered, bullate, 
©.2-0.4 mm. across, long covered by the overarching and conspicu- 
ous epidermis, deep seated, arising from below the palisade layer, 
compact, chestnut brown; teliospores ellipsoid, 24-28 by 32-40 yn, 
rounded at both ends, slightly or not constricted at septum, wall 
light chestnut brown, 3-4 u thick, slightly thickened over the pore 
of either cell, 4~—5 u, rather prominently and sparsely verrucose, with 
conical projections; pedicel colorless, once to twice length of spore. 
On Vernonia triflosculosa H.B.K. , Mazatenango, Guatemala, February 21, 
1916, Holway 510 (type); San Jose, Costa Rica, II, III, January 10, 1916, 
Holway 407; San Ramon, Costa Rica, January 13, 1916, II, Holway 426; 
Heredia, Costa Rica, December 17, rots, I, Holway 262. 
A very distinct species, separable from all others on Vernonia by the very 
deep seated, strictly epiphyllous sori, arising from beneath the palisade layer 
of leaf tissue. The sori are aggregated in ayo groups, presenting the appear- 
aig on cursory examination, of a micro-form. It is quite different from 
P. idonea (cf. 17), which occurs on the same host from the same region. 
21. PUCcINIA ROTUNDATA Diet. Hedwigia 36:32. 1897.—P. 
rugosa Speg. Ann. Soc. Cient. Argent. 17:92. 1884; not P. rugosa 
Billings 1871. 
O. Pycnia amphigenous, among the telia, few, gregarious, 
noticeable, yellowish, subepidermal, globose or somewhat flask- 
shaped, 125-130 by 125—130 u, ostiolar filaments not extruded. 
III. Telia amphigenous or chiefly epiphyllous and caulicolous, 
numerous, crowded on yellowish spots in orbicular or somewhat 
irregular areas, o. 5-5 mm. across, roundish, 0.2-0.5 mm. across, 
tardily naked, becoming pulverulent, reddish brown, ruptured 
epidermis conspicuous; teliospores ellipsoid, 18-26 by 30-42 #, 
rounded at both ends or occasionally tapering below, not or slightly 
constricted, cells easily separating; wall cinnamon brown, uniformly 
thick, 2.5—3 u or occasionally thickened to 4-5 mu over pores, which 
are located about half way from apex to septum in the upper cell 
