650 Trow. — The Karyology of Saprolegnio . 
Zimmermann, A., ’92 : Die Botanische Mikrotechnik. Tubingen. 
Zopf, W., ’82 : Ueber Parasiten in den Antheridien, Oogonien und Oosporen von 
Saprolegnieen. Bot. Centralblatt, Bd. XII, S. 356. 
’83 : Erwiderung. Bot. Centralblatt, Bd. XV, S. 156. 
EXPLANATION OF FIGURES IN PLATES 
XXIV AND XXV. 
Illustrating Mr. Trow’s paper on the Karyology of Saprolegnia. 
The outlines of all important structures in the figures were traced with the 
camera lucida and the details then filled in by freehand. The highly magnified 
figures of the separate nuclei were, however, drawn entirely by freehand. Those 
referring to S. dioica were drawn from preparations stained with Schneider’s acetic 
carmine and with the aid of Zeiss’s apochromatic 2 mm. objective (aperture 1-3) 
and the compensating ocular 4. The magnifications given were determined by 
measurement. 
The other figures were drawn from preparations stained with gentian-violet and 
eosin and with the aid of Zeiss’s achromatic homogeneous immersion objective 
(aperture 1*3) and the Huyghenian oculars 2 and 4. 
All the nuclei in a section have as a rule been represented by reducing them to 
the same optical section. Sections in which there were nuclei overlying one 
another were rejected as unsuitable. 
Abbreviations : an. antheridium ; ch. chromosome ; c. w. cell-wall ; deg. n. 
degenerate nucleus ; d. 71. dividing nucleus ; f. g. n. female gameto-nucleus . 
g. n. gameto-nucleus ; m. g. n. male gameto-nucleus ; n. nucleus ; n. m. nuclear 
membrane ; nn. hy. nucleo-hyaloplasm ; oog. oogonium ; v. vacuole. 
S. mixta , De Bary. 
Fig. 1. a. Resting zoospore showing the structure of the nucleus. The deeply 
stained granules between the nucleus and the vacuole disappear before germination. 
b , c, and d. Germinating zoospores showing the division of the nucleus, and the 
formation of the germ-tube. The nuclei in d were further apart than they appear to 
be, the close grouping being partly due to the necessary process of reducing them 
all to the same optical section, x 1 1 50. 
Fig. 2. a and b. Hyphae: a is a tangential section, b has been sectioned at 
various angles. The nuclei in b are abnormally elongated. xn 50. 
Fig. 3. a. Transverse section of a nearly mature sporangium. The arrows 
A and B point in the direction of two zoospore-rudiments whose nuclei were 
respectively above and below the optical section figured, x 1290. 
