The Development of Thraustotheca, a Peculiar 
Water-Mould . 1 
BY 
WILLIAM H. WESTON, A.M., Ph.D. 
With Plates IV and V and two Figures in the Text. 
T HE genus Thraustotheca comprises at present the single species 
T. clavata (de B.), Humph., and is a rare and imperfectly known 
representative of the Saprolegniaceae. In the following paper the writer 
presents certain results of a culture study on the development of this 
fungus. These investigations were carried on in the Cryptogamic Labora¬ 
tories of Harvard University under the direction of Dr. Roland Thaxter, 
for whose helpful criticism and advice the writer wishes to express his 
gratitude. 
History. 
Thraustotheca clavata (de B.), Humph., was first discovered in 1880 by 
de Bary in a culture from algae collected at Vendenheim near Strassburg, 
and was named by him Dictyuchus clavatus , since its method of spore 
liberation resembled somewhat that of the genus Dictyuchus established by 
Leitgeb (19) in 1869 . Under this name Biisgen ( 6 ) published the first 
description of the species in his study of sporangium formation in this and 
other Phycomycetes. In .1884 de Bary (3) mentioned the fungus as an 
example of endogenous cell formation, and in 1887 Rothert (24) briefly 
discussed the process in this and other forms. The first full description of 
the species, with illustrations, was given in 1888 in a posthumous paper of 
de Bary’s (4) edited by Solms-Laubach. The latter suggested that certain 
peculiarities of the fungus, especially the disintegration of the sporangium 
membrane, might prove sufficient basis for establishing a new genus; and 
this was also urged by Fischer (11) in a later discussion of the species. 
Humphrey (15), although unable to secure Dictyuchus clavatus for study, 
considered it a species sufficiently aberrant to justify separation from the 
genus. On this species as a type he established the genus Thraustotheca , 
which has since been accepted by Schroter (26) and other systematic 
writers. A little more than thirty years after the fungus was first discovered 
1 Contribution from the Cryptogamic Laboratory of Harvard University, No. 80. 
[Annals of Botany, Vol. XXXII. No. CXXV. January, 1918.] 
