KING: CYTOLOGY OF ARAIOSPORA PULCHRA. 
213 
It is interesting to note that Araiospora and its relatives when 
first described were placed by Cornu in the Saprolegniaceae where 
Pringsheim (’58) had previously placed the genus Pythium. De 
Bary, however, who afterward carefully studied the Peronospora¬ 
ceae , saw the close relationship between this family and the genus 
Pythium and included the latter as a separate genus of the former. 
He also suggested, although he had seen only a note by Cornu in 
regard to Rbipidium, that it, too, might possibly belong near 
Pythium. 
Fischer ('92) accepted de Bary’s arrangement of Pythium but left 
Rhipidium as a genus of the Saprolegniaceae . 
Schroeter (’93) included the three following families in the Sapro- 
legniineae : the Saprolegniaceae , the Leptomitaceae , to which both 
Araiospora and Rhipidium belong, and the Pythiaceae. In this 
classification the family Leptomitaceae is distinguished from the 
other two by the fact that its members have well marked constric¬ 
tions in their hypliae. 
In the paper which has been referred to previously, Thaxter 
suggests that in case Scliroeter’s classification is not accepted, the 
Leptomitaceae should be united with the Pythiaceae if the latter is 
viewed as distinct from the Peronosporaceae , but if not, then both 
should be included in the Peronosporaceae . 
Description. 
Both genus and species have been diagnostically described and 
figured by Thaxter (’96). A single individual consists of a large, 
elongated, subcylindrical, basal cell 1 to 1.5 mm. long by ‘25 to 50 
[x in diameter, that has at its apex or near the upper end, which 
is more or less conical, a variable number of hyplial filaments that 
extend upward and outward from their places of attachment; and 
at the lower end, rhizoid-like processes which serve to attach the 
plant to the substratum (7. c., pi. ‘23, fig. 22). At the distal end of 
these hyplial filaments, large subcylindrical or broadly clavate zoo¬ 
sporangia are produced in whorls or umbels. Each of these zoospo¬ 
rangia, when mature, opens at its outer end by a papilla of 
dehiscence that forms a perforation through which the zoospores, 
surrounded by a delicate membrane, escape from the zoosporangium. 
