Davis . — Spore Formation in Derbesia. 19 
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EXPLANATION OF FIGURES IN PLATES I AND II. 
Illustrating Dr. Davis’s paper on Derbesia. 
The preparations were studied under the Zeiss apochromatic oil immersion 1-5 mm. with the 
compensating oculars. The figures were sketched with an Abb6 camera from sections generally cut 
3 \x thick and stained with iron-alum haematoxylin after the method of Heidenhain. The magnifica- 
tion was as follows: Fig. 1, 1000 diameters; Figs. 2, 12, 13, and 27, 667 diameters; Figs. 6-9, 
14-26, 28, and 29, 1334 diameters; Figs. 10, 11, and 30-32, 2000 diameters. 
PLATE I. 
Fig. 1. Zoospore in side view, stained with iodine to show circle of cilia. 
Fig. 2. Zoospore shortly after coming to rest, viewed from above, stained with iodine. 
Fig. 3. Outline of a sporangium in section, the protoplasm of which is still in communication 
with that of the parent filament. 
Fig. 4. A stage in the formation of the cross partition at the base of the sporangium ; there is 
present a ring-shaped thickening growing inward from the periphery and showing a laminate 
structure. 
Fig. 5. The cross partition at the base of a sporangium showing the laminate structure. 
Fig. 6. The nuclei as they enter the sporangium, illustrating their relative size in comparison 
with the plastids ; each nucleus contains a small nucleolus and a large chromatin body. 
C 2 
