1923] A New Species of Thraustotheca 113 



long, 55-100/i, thick -with smooth walls, borne on lateral stalks which 

 in length are from once to twice the diameter of the oogonia ; oogonial 

 stalks usually once coiled, not rarely straight. Eggs 1-8 in an 

 oogonium, 42-60fji thick, rarely up to 77/i, thick, but when so large 

 always single in the oogonium; often crowded and elliptical from 

 pressure; structure as in A. apiculata with a central sphere of proto- 

 plasm surrounded by oil droplets ; wall of the egg about 4/x thick. 

 Antheridia apparently not always developed, but when visibly present 

 quite often arising from the oogonial stalk, not rarely diclinous, one 

 to several on an oogonium ; antheridial tubes developed. 



Found twice at Chapel Hill, from Battle's Branch (October, 

 1922) and from the branch below Cobb Terrace (November, 1922). 

 The description is made and all figures except No. 10 are drawn 

 from a single spore culture of the last collection. This remarkable 

 plant differs from all other water molds in the details of spore be- 

 havior and discharge, but the essentials of this process are like those 

 in Thrmistotheca and it is best to consider it a species of that genus. 

 In Thraustotheca it has not been noted that the spores swell locally 

 in a certain area of the sporangium, but it seems to me probable that 

 this is the case. It is certainly so to a marked degree in the peculiar, 

 intermediate species, Achlya duhia Coker (Saprolegniaceae, p. 135. 

 1923). The angular shape of the encysted spores is also a Thrausto- 

 theca character and is a result of the early encystment while still 

 under compression in the sporangium. 



It is very probable that some mucus material is the cause of the 

 extension of the spores though no one has yet been able to demonstrate 

 it. The discovery of the species Achlya duhia has already broken 

 down any sharp distinction between Achlya and Thraustotheca, as 

 some of its sporangia behave as in Achlya and others as in Thrausto- 

 theca. The present species makes a distinction still more difficult by 

 introducing a new combination of features, an elongated, subcylin- 

 drical sporangium becoming truncated by the separation of a cap and 

 the spores escaping by slow degrees in angular shapes after encyst- 

 ment. In order to include the present species and exclude Achlya 

 duhia the genus may be defined as similar to Achlya except that the 

 spores encyst in an angular shape in the sporangia and in all or most 

 cases escape by slow degrees by oozing out after the cracking of the 

 sporangium, in no case escaping promptly through an apical papilla. 

 It is unfortunate that the egg structure in the two species of Thraus- 



