on the Saprolegnieae . 203 
of the zoosporange, its septum, and the tubular process 
through which the spores escape. On these grounds I think 
it is well worth abstracting to show exactly what is our 
present knowledge of this most interesting study ; and I shall 
supplement this abstract by criticisms of all points on which 
my own work has led me to take a different view to the 
author’s. 
Rothert’s work was principally conducted on three forms of 
Saprolegnia belonging to the ferax group. A well-chosen 
field is half the battle ; it is very difficult in working over a 
group to give equal attention to each ; and he has shown 
that these species are far more favourable than Dictyuchus 
(genus) or Achlya 1 . 
The sporangial formation begins by the slackening to final 
1 The following brief analysis of the genera may prove useful to readers : — 
Saprolegnia. — Spores leaving the sporange and swarming freely, then encysting to 
swarm later in the 1 second form.’ Innovation usually growing through the 
empty sporange. 
Leptomitus. — Resembling Saprolegnia , but with frequent strangulations on hyphse 
and sporangia. As these occur also according to Cornu, in forms otherwise 
referable to Achlya ( Achlyogeton Schenk,) and Pythiuni (. Myzocytium Schenk), 
I regard them as mere habit characters, of less worth probably than the septa 
of Saprolegnia lorulosa, which De Bary regards nevertheless as scarcely more 
than a form of S. ferax. Hence it is that I described (‘ falschlich,’ as Rothert 
writes) as a Saprolegnia , a form with constricted hyphse, but with the innova- 
tions growing into the empty sporangia, and with the sexual reproduction 
of S. ferax. 
Achlya. — Spores on their liberation assembling to encyst in a hollow sphere at the 
mouth of the sporange, then swarming in the second form ; innovation growing 
out laterally at the base of the empty sporange. 
Aphano?nyces. — Like Achlya , but with linear sporangia containing only a single 
file of zoospores ; innovation growing into the empty sporange. 
Dictyuchus (genus). — Spores do not leave the sporange but encyst in situ, 
emerging only in the second form. The sporange wall often deliquesces at 
the maturity of the spores. 
‘ Dictyuchus form.' — 'When the spores of Achlya or Saprolegnia fail to leave it at 
maturity they encyst within, constituting this form or dictyosporange. They 
either swarm ultimately in the second form or germinate in situ by emission 
of a hypha. 
The ‘ first form ’ of zoospore is ovoid with a pair of flagella from the front (narrow 
end). The * second form ’ is uniform with an anterior and a posterior flagellum 
diverging from the hilum. The existence of these two forms constitutes the phe- 
nomenon of ‘ diplanetism.’ 
P 2 
