CHYTR1DIALES 321 



the female plant and its contents flow into the latter. In a few instances 

 no males were attached to the resting spore. These may have been 

 parthenogenetically developed. After fusion, the wall of the neck in 

 the female thickens, from the outside inward, normally to produce a 

 solid, highly refractive core. The neck varies in length, but often is 

 narrowed where it joins the base (the actual resting spore). A mature 

 spore is oval to spherical, 7.5-13 \x in diameter, with a thick wall that 

 may be smooth, granular, or distinctly spiny. The contents are oily, 

 usually with many scattered droplets but sometimes with a single 

 large globule. 



The zygote germinates readily in the laboratory. A thin-walled spo- 

 rangium forms on the surface of the resting spore. The latter functions, 

 therefore, as a prosporangium. The zoospores are posteriorly flagellate. 

 Like the zoosporangia, the germ sporangia yield zoospores of one 

 type, either with a single oil globule or with a globule and an oscillating 

 granule. 



Although the chytrid Canter found agrees in the main with Dan- 

 gear -dia mammillata, it differs from that of Schroder's original de- 

 scription in having the resting spores epibiotic and sexually formed. 

 She believes Schroder misinterpreted the spore as endobiotic, since 

 a resting spore viewed from above a host cell often may appear so. 

 The epibiotic position of the resting spore has been confirmed for 

 Dangeardia laevis by Sparrow and Barr (1955). 



KEY TO THE SPECIES OF DANGEARDIA 



Resting-spore wall spiny, warty or sometimes smooth, sexually formed 



D. mammillata, p. 321 

 Resting-spore wall always smooth, asexually formed .... D. laevis, p. 322 



Dangeardia mammillata B. Schroder 

 Berichte Deutsch. Bot. Gesell., 16: 321, pi. 20, figs. 1-14. 1898 

 (Fig. 19C-E, p. 318) 

 Sporangium flask-shaped or pyriform, with a somewhat prolonged 

 apex, 10-30 \x long by 7-20 [x in diameter, wall smooth, colorless, slight- 

 ly thickened; rhizoids short, bushy, generally unbranched; zoospores 

 of two types, spherical, 2.5 \x in diameter with a single colorless oil 



