CHAP, II.—DIFFERENTIATION OF THE THALLUS.—SIMPLE SPOROPHORES. 47 
put out branches bearing new sporangia. There is here therefore a cymose branching 
of the sporangiophores. 
The gonidiophores in Peronospora, which are also without transverse septation, 
are repeatedly forked or monopodially paniculate. The branches are all at first 
narrowly conical, and when their longitudinal growth is completed their terminal 
portions swell into an ovoid form, as.is seen in Fig. 20a, and are abjointed to form 
gonidia, and with this the de- 
velopment of a gonidiophore 
of Peronospora comes to an 
end. But in the nearly allied 
genus Phytophthora after 
the abjunction of each goni- =. 
dium the narrow end of the 
branch which bore it swells 
slightly immediately beneath 
it, and elongating at the same 
time pushes the gonidium so 
a 
much to one side that it pre- Fi 
sently forms a right angle 
with the pedicel. Then in P. 
infestans the gonidiophore 
swells at the point of attach- FIG. 20. Phytophthora infestans, extremity of two simple sporophores. a forma- 
eqs u tion of the first gonidia on the tip of each branch. &two ripe gonidia on each branch, 
ment of the gonidium Into @ with the beginning of the formation of a third. Magn. about 200 times. 
small narrowly flask-shaped 
vesicle, and its upper end elongates at the same time and again assumes the character 
of a gonidia-forming point. After a time a gonidium is formed on it in the manner 
described above, and the process is repeated usually three or four times on the same 
gonidiophore, or as many as twelve or fourteen times in luxuriant plants. Older simple 
gonodiophores therefore, when examined dry, are 
seen to bear a number of lateral nearly equidistant Ge 

gonidia forming a right-angle with the gonidiophore, 
and each standing on a flask-shaped swelling 
(Fig. 202). As the ripe gonidia fall off instantly 
in water, preparations treated with water have the 
older branches of the gonidiophore swollen at inter- 4 
vals into the shape of a flask with a single unripe 
gonidium at most at its apex. ; a b c 
The simple sporophores of Haplotrichum, 
Gonatobotrys, and Arthrobotrys (Fig. 21) are | 
short erect rows of cylindrical cells usually simple, 
but sometimes with single branches. The apex of z 
the uppermost cell swells up considerably in Haplo- 
trichum, slightly in the other species, and puts out 
numerous crowded protuberances, which together ges 
form a small spherical head and develope into —— 
gonidia. This is the whole of the development in : ; 
Haplotrichum. But in the other two forms the ee 
apex of the gonidiophore begins to lengthen again A neue ad Eon. bascond head 
after the first head is matured and grows through of five successive heads. After Fresenius (Beitr). 
it, and thus the head becomes a whorl surrounding me 
the flanks of the gonidiophore; the growing end 
of the gonidiophore attains to about the length of one of its lower segments, be- 
comes septate above the first head and then forms a new head at its extremity like 
the first. This proceeding may be repeated several times, till the gonidiophore is at 



