136 Trow . — Observations on the Biology and 
Sporangia, terminal, cylindrical, scarcely thicker than the supporting 
hyphae, of a length generally varying from 250 /x to 368 /x, and of 
a breadth varying from 39 p to 72 /x (average of six measurements — 
length=3i5 /x, breadth = 56 jx) ; sometimes very small, producing in 
extreme cases no more than three or four zoospores ; generally 
developed in the typical cymose order, the main axis , however , 
frequently septate behind the oldest sporangium , each segment thus formed , 
of which there may be as many as ten, developing a short branch , the 
segment and branch together constituting a sporangium. 
Spores very numerous, averaging 13^ in diameter, generally 
encysting at the mouth of the sporangium, occasionally, however, 
inside it. 
Oogonia, on short unbranched stalks, which are about as long as 
the diameter of the oogonium, and of an average breadth of 10/x; 
at first developed regularly in racemose order on the main hyphae ; 
generally terminal and spherical, but not infrequently intercalary and 
barrel-shaped ; of a diameter 31 /x to 85 n (average of twelve measure- 
ments=6o ju), with a thick, pitted, yellowish smooth wall; frequently , 
however , provided with blunt spines , which may exceptionally even reach 
the length of 2 5 /x, and are due to outgrowths through the pits. 
Antheridia, always present under natural conditions,/^ in number , 
produced on branched antheridial filaments of a diameter of 6- 5 /x, 
which arise from the main hyphae side by side with the oogonial 
branches, or, as observed in a very few cases only, from the stalk of 
the oogonium ; of very variable shape, but generally long and curved, 
and closely applied throughout to the surface of the oogonium, or 
opposite the pits only by means of outgrowths from the under 
surface; sometimes septate; of a maximum length of 65^ and 
maximum breadth of 7 /x ; emitting from points in contact with the 
pits one or more branched or unbranched fertilization-tubes of a 
diameter of 4 /x. 
Oospores, one to twenty or more, mostly from three to eight 
(average of twelve cases =6) ; spherical, with a smooth , very thick two- 
layered wall ; eccentric, of a diameter of 23 /z to 26 /x, and having an 
oil-globule of a diameter of 15 /x ; germinating at once, and producing 
a long, thin, branched hypha, or one or more small sporangia, or 
passing into a resting condition and remaining capable of germination 
for at least four months. 
