1032 Butler.*—On Allomyces ) a new Aquatic Fungus . 
Leptomitaceae) or Monoblepkaris. This suggestion was first made by 
de Bary and has since been adopted by many botanists. Petersen admits 
that possibly the i-ciliate series is derived from certain Algae, without 
any intermediate stage of myceliated Phycomycetes. If the latter, then 
the algal ancestors of the 2-ciliate series must have been closely related to 
those of the i-ciliate forms. It would take too long to follow him here, 
but one point deserves special attention. Like Atkinson he does not 
consider that the i-ciliate and 2-ciliate species need necessarily indicate 
two distinct groups, but there are nevertheless differences between them of 
great importance. He makes the general statement that the membrane 
of all the species with 2-ciliate zoospores contains cellulose, while most of 
the i-ciliate forms are without this substance, and only a few (endophytic) 
forms have traces of it. If this is true (and we have seen above that it 
holds good for the Leptomitaceae) it is probably a generalization of great 
significance. 
Vuillemin (’ 07 ) and Lotsy (’ 07 ) have been still more impressed by the 
differences between the i-ciliate and 2-ciliate groups. They refer the latter 
to the series of the Isocontae of the green Algae. But Vuillemin adopts 
the Monadine theory of the origin of the i-ciliate series, and Lotsy derives 
them from many lower organisms, more simple than the Isocontae. To 
both, Monoblepkaris is a stumbling-block. Vuillemin (’ 07 , p. 106) says 
of this genus : ‘ (Test un genre exceptionnel par ses organes reproducteurs 
comme par ses organes sexuels. II a des allures de genre primitif avec ses 
spermatozoides, uniques parmi les champignons filamenteux. II n’a pas 
de parente plus plausible avec les autres champignons qu’avec les Algues 
vertes, telles que les CEdogonium auxquels Lagerheim le compare, ou avec 
les Vaucheria qui en seraient les ancetres d’apres Thaxter. II est done 
a souhaiter que ses affinites soient precis^es par la decouverte de formes 
nouvelles.’ 
I think that a consideration of the characters of the Leptomitaceae 
brought into evidence by the new Fungus above described may help to 
diminish these difficulties. On the one hand, Monoblepkaris is brought into 
probable relationship with a group of aquatic Phycomycetes in which the 
zoospore may be 1- or 2-ciliate, the thallus segmented or not, and the 
membrane with or without cellulose. On the other, the members of this 
group show marked signs of affinity with the green Algae. The form 
described by Ernst (' 02 ) as Dickotomosiphon ^ an ally of Vaucheria , is extra¬ 
ordinarily like Allomyces ’in several respects. From a common stalk fertile 
branches arise, chiefly dichotomously. These branches are constricted at 
their origin and segmented at intervals by a ring which does not entirely 
occlude the passage. The cell-wall gives the ordinary reactions of cellulose, 
except that it is coloured yellow by chloriodide of zinc. Though this 
Alga forms starch, its nearest ally Vaucheria does not. The position of 
