54 
The Ohio Naturalist. 
[Vol. X, No. 3, 
EXPLANATION OF PLATES III AND IV. 
All figures are camera drawings from sections. All except 
Figs. 1, 3-7, were made with a Spencer 1.5 mm. immersion 
objective and compensating ocular 4 giving a magnification of 
approximately 670 diameters. Fig. 1 was drawn with an 8 mm. 
objective and 4 ocular giving an approximate magnification of 
125 diameters; Fig. 3 with the 1.5 mm. objective and 3 ocular, 
magnification 533; Figs. 4-7 with objective 1.5 and ocular 12, 
magnification 2130. The plates were reduced to 2-3 of their 
original size exactly eliminating the enlargement due to the 
camera and rendering them the same size as seen in the 
microscope. 
PLATE III. 
Fig. 1. 
Fig. 2. 
Fig. 3. 
Fig. 4. 
Fig. 5. 
Fig. 6. 
Fig. 7. 
Fig. 8. 
Fig. 9. 
Fig. 10. 
Fig. 11. 
Fig. 12. 
Fig. 13. 
Fig. 14. 
Fig. 15. 
Fig. 16. 
Fig. 17. 
Fig. 18. 
A tangential section through the hypodermis of the wing of the 
petiole of the Ragweed, showing the general relations of the 
parasites to the tissue of the host. R. Sp. Resting Spores, 
Z. Sp. Zoosporangia. 
A cell with numerous amoebid zoospores imbedded in the host 
cytoplasm; one pair of zoospores conjugating; cell distorted 
by an adjacent zoosporangium measuring 45 x 60 //, note 
slight degree of injury. 
A tangential section of a host cell wall showing perforations 
where the parasites entered. 
One of the zoospores from Fig. 2. 
Zoospores just beginning to conjugate. 
Conjugating zoospores. 
Conjugation complete. 
A cell with two young zygotes, each binucleate, and several 
unconjugated zoospores; note cellulose plugs marking the 
points where the parasites entered. 
A young zygote. 
Zygote nearly full grown. 
A young resting spore; note slight injury to the nucleus and 
cytoplasm of the host cell. 
Two ripe resting spores within same host cell; each binucleate 
though the nuclei of the lower spore do not lie within the 
plane of section. 
A cell with two young parasites; a probably the first division 
(amitotic) of the zoospore; b, a plasmodium with four nuclei; 
on the wall are shown the plugs marking the points of 
entrance. 
A young plasmodium with eight nuclei most of which are in 
process of amitosis ; central vacuole developed unusually early. 
A plasmodium with about 60 nuclei; central vacuole beginning 
to appear; note relations of parasite and host nucleus. 
A larger plasmodium with well developed central vacuole lying 
in the chlorenchyma of its host; note slight injury beyond 
mechanical distortion. 
A full sized plasmodium with very many nuclei. 
A ripe zoosporangium; opening at top may be natural or due 
to knife. 
