UREDINALES OF GUATEMALA 
477 
over, there is a remarkable and significant similarity in the size and 
sculpturing of the aeciospores and urediniospores, not taken into 
account in the published comments on the South American material, 
although to be seen in the type material as well as in that from Guate- 
mala. For convenience a full technical description is appended. 
The generic name of the host was written Arracacha at one time, but is 
now accepted in the form Arracacia. 
Pycnia chiefly epiphyllous, few, subepidermal, chestnut-brown, 
globoid, 150-220 IX in diameter. 
Aecia amphigenous, in groups of 2-6 with the pycnia, o.i or 
less in diameter; peridium wanting, the sorus bounded by a thin layer 
of mycelium; aeciospores angularly ellipsoid or oblong, 18-23 by 24- 
35 IX] wall colorless, 2-2.5 ix thick, variably verrucose, sometimes 
appearing echinulate. 
Uredinia hypophyllous, scattered, round, 0.2-0.5 mm. across, 
early naked, pulverulent, yellow or pale cinnamon-brown, ruptured 
epidermis evident; urediniospores ellipsoid or obovoid, 18-24 by 29- 
37 ix\ wall colorless or yellowish, moderately thick, 1.5-2.5 /x, closely 
echinulate, the pores obscure. 
Telia hypophyllous, scattered, round, 0.4-0.6 mm. across, early 
naked, pulvinate, chestnut-brown, ruptured epidermis inconspicuous, 
germinating readily in the sorus; teliospores ellipsoid or oblong, 21-29 
by 34-51 At» round at both ends, or slightly narrowed below, little 
constricted at septum; wall cinnamon-brown, thin, 1-2 ^u, much 
thicker above, 5-10 /x, smooth; pedicel colorless, once and a half 
length of spore or less, tapering downward. 
146. Puccinia obscurata Arthur & Holway sp. nov. (on Ammiaceae). 
Neonelsonia ovata Coult. & Rose, Volcan de Agua, Dept. Sacate- 
pequez, March 4, 1916, II, III, 555. 
Uredinia chiefly hypophyllous, scattered, round or oval, 0.1-0.8 
mm. across, early naked, pulverulent, pale cinnamon-brown, ruptured 
epidermis evident; urediniospores globoid or obovoid, 18-26 by 24- 
29 ix\ wall colorless or light-yellow, moderately thick, 1.5-2.5 jx, 
closely echinulate, the pores rather indistinct, 2-3, usually 2, equato- 
rial. 
Telia hypophyllous, scattered, round, 0.1-0.3 mm. across, early 
naked, somewhat pulverulent, chestnut-brown, ruptured epidermis 
evident; teliospores broadly elHpsoid or oblong, 23-31 by 30-40 ix, 
rounded at both ends, slightly or not constricted at septum; wall 
cinnamon-brown, thin, 1-1.5 ix, thicker above, 3-7 ix, smooth; pedicel 
colorless, longer than the spore, fragile, and usually broken away. 
The microscopic appearance of this rust gives much the same im- 
pression as that of P. Arracacharum, on Arracacia, but the detailed 
