(JO THE FLORA OF NEBRASKA. 



Peronospora oxybaphi Ell. & Kell. Jour. Myc. I., 2. 1885. 



Sori white, broadly effused, hypophyllous; conidiophores elongate, 3 4 times 

 diohotomously branched; sterigmata short, blunt, curved, 12-15 fi; conidia 

 rotund or ellipsoid, brownish, 20-23x15-17 /i; oospores globose, 45-50 u in 

 diam.; epispore thick, brown, minutely tuberculate. 



In leaves and young shoots of Allionia nyctaginea; Ashland, Weeping Water. 



Peronospora eft'nsa (Grev.) Rabenh. Herb. Myc. no. 1880. 

 Botri/tis effusa Greville Flor. Edin., 468. 1824. 

 Peronospora chenopodii Schlecht. Bot. Zeit. 1852, p. 619. 



Sori thin, yellowish, hypophyllous; conidiophores short, stout, 3-4 times 

 branched above; sterigmata 12-15 /i, greatly curved; conidia elliptical, 

 grayish, 30-38x18-23 ft; oospores small, globose, 20-30 u; epispore brown- 

 ish-fuscous, very conspicuously tuberculate. 

 In leaves of Chenopodium album, Lincoln. 

 B. Oospore smooth, or with the epispore inconspicuously plicate. 



Peronospora potentillae DeBary Ann. Sci. Nat. Bot. 4, XX., 124. 1863. 



Sori yellowish, thin, scattered, hypophyllous; conidiophores elongate, slen- 

 der, 3-5 times dicbotomous; sterigmata subulate, arcuate, 12-15 (i long; 

 conidia ellipsoid, brownish, 15-18x24-27 //; oospores globose, 22-24 p\ epi- 

 spore smooth, yellow. 



On Potentilla sp., Lincoln. 



Peronospora parasitica (Pers.) Fr. Summ. Veg. Scand., 493. 1849. 

 Botrytis parasitica Pers. Obs. Myc. I., 96. 1796 



Sori broadly effused; conidiophores short, stout, irregularly 3-6 times dicho- 

 tomously branched; sterigmata elongate, blunt, very strongly arcuate or 

 bent; conidia ellipsoid, white, 19-24x25-27 (i; oogones globose, 45-50 fi; 

 oospores spherical, 30-38 fi; epispore thick, smooth, yellow. 

 In leaves and stems of Bursa bursa-pastoris, Lepidium incisum, L. virgini- 

 cum, Sisymbrium pinnatum and S. officinale. Lincoln, Havelock, Saltillo, 

 Ashland, Wabash. PI. XVI., Fig. 2, a, b. 



Order 6.— COKFERVOIDEAE- Thallus chlorophyll-green, pericellular, filiform 

 or rarely membranaceous; cells either uniseriate, forming a simple or 

 branched filament, or pluriseriate, forming a more or less expanded thallus ; 

 propagation by motile cells, zoospores, or non-motile cells— aplanospores; 

 reproduction wanting, or taking place in the lower families by copulation 

 of zoospores and in the higher families isogametic or heterogametic. 



SYNOPSIS. 



Fam.— Ulvaceae.— Thallus tubular or foliaceous,rarely filiform, simple or branched; 

 chloroplasts in parietal laminae; propagation by zoogonidia; reproduc- 

 tion by copulation of zoospores. 



Fam.— Ulotricliiaceae.— Thallus filamentous, simple or branched; mostly of one 

 row of cells; terminal cell in many cases ending in a hyaline awn or 

 thread; chloroplasts single in bands or rin*s, margins often laciniate; 

 propagation by zoogonidia; reproduction by the copulation of microgon- 

 idia. 



