468 Bulletin 315 



of the sporangium. The conidia are often provided with thick walls, 

 showing a distinct double contour Sexual organs have not been observed. 



Hab. vSaprophytic in garden soil, Cork, Kew, Great Britain; Paris, 

 Antibes, France; and Freiburg i. Br., Germany, Butler. Parasitic in 

 prothallia of Equisetum, Todea, and Ceratopteris, Germany. Parasitic 

 in fern prothallia (not further specified). Cornell University, New York 

 State, U. S. A., Atkinson. 



Pythium vexans de Bary, Jour. Bot. 5: 119. 1S76; Jour. Roy. Agr. 

 Soc. England ser. 2, 7: 339. fig. 6. 1876; Bot. Ztg. 39: 537. pi. 3, figs. 

 3-7. 1881. Butler, Mem. Dept. Agr. India No. 5, i: 91-94. pi. 5, figs, 

 i-io. 1907. 



The mycelium is slender, finer than that of P. de Baryanum Hesse or 

 P. rostratum Butler, but resembling P. intermedium de Bary both in the 

 thickness of the hyphas and the size of the thallus in water cultures. The 

 branches of the secondary or tertiary order often extend far beyond the 

 primary hyphas, tapering into very fine filaments at the ends. This 

 character distinguishes this species from all others. 



Sporangia and conidia are developed on two- or three-days-old cultures. 

 The former are rare. They occur both terminally and, more rarely, 

 intercalarily, and are scarcely ever spherical or oval, but usually irregularly 

 pear-shaped ovoid or subangular. The sporangial tube of discharge is 

 short, and the zoospores are given only when the sporangia are sown 

 immediately in fresh water. The sporangia and the conidia measure 

 17-24/X in diameter, averaging about 21 n. A second conidium is some- 

 times budded off from the first by a continuation of growth before the 

 first is cut off by its basal septum. There are irregular intercalary swell- 

 ings from which one or more branches arise. 



The oogonia are 22-25/i in diameter. They arise laterally usually 

 on short branches from the main hyphoe, or sessile on the latter. The 

 oogonium is usually inserted on its stalk by a broad base. The anther- 

 idia usually arise from the oogonial stalk and are sometimes hypogonal. 

 The antheridial cell is club-shaped or rounded, and large in relation to 

 the oogonium. Oospores free in the oogonium, 20-22/i in diameter, 

 smooth, round. 



Hab. Saprophytic in garden soil, Cork, Kew, Great Britain; Antibes, 

 France, Butler. Saprophytic in potatoes, Germany, de Bary. 



Pythium proliferum de Bary, Jahrb. Wiss. Bot. 2: 182. pi. 21. i860. 

 Ward, H. M., Quart. Jour. Mic. Sci. n.s. 22: 497. pis. 34-35, figs. 11-21. 

 1893. Dangeard, Recherches histologiques sur les Champignons. Le 

 Botaniste 2: 123. pi. 6, figs. 39-48. 1890. Butler, The Genus Pythium 

 and Some Chytridiaceae. Mem. Dept. Agr. India No. 5, i: "i^-Ti- pis. 

 3-4, fig. I. 1907. 



