1900] CHANGE OF FORM IN GREEN ALG 315 
* Professor C. R. Barnes, of the University of Chicago, for aid in its 
| completion. Also, I take occasion here to acknowledge with 
thanks much kind assistance regarding physical chemistry ren- 
dered me by Dr. K. E, Guthe, of the University of Michigan. 
THE UNIVERSITY oF CHICAGO. 
EXPLANATION OF PLATES XVII AND XVIII. 
All of the figures are reproductions of photomicrographs taken with a 
Zeiss camera and Zeiss microscope. The first five are magnified about 450 
diameters, the rest onlyabout 140. All but figs. s—5 were taken as the plants 
lyin or upon the nutrient medium in the culture dish. The others were 
made from slide mounts in water. 
PLATE XVI, 
Fig. 1, Typical palmella form. a. Vegetative cell, showing clear area 
"covered by chloroplast. 4. The same, but preparing to produce z00- 
Spores. c, Cells which have divided, but whose daughter cells are not yet 
Separated, 
Fic, 2, Typical filaments. 
Fig, 3. Zoospores, immediately after they have come to rest. The clear 
area is the part of the periphery not bounded by the chloroplast. 
Figs. 4 and 5. Typical filaments changing to the palmelia form by 
rounding and Separation of cells. 
Fig, 6, Culture no. 50. Exposure May 10. Typical palmella cae 
la at the right shows a parenchymatous colony. This was used for 
es Material in many of the following cultures. : oe 
ie 7. Culture no. 144a. Palmella from no. 50 put into K, pete 
“ad i soe Exposure May 28. Original palmella masses with long: eat 
m at Periphery, Also young filaments from zoospores. The original 
MASSES are Out of focus, 
ay 8. Culture no. 1472. Palmella from no. 50 put into C, 96. wie 
Pe "900. Exposure May 28. Original masses have grown out into 
—. whose older cells have rounded. Many young filaments from 
“spores, 
eM Culture no, 132@. Palmella from no. 50 put into K, 1928 V x 
a On May 23 many new filaments had been produced as 
i i . None ott 
nginal aieine rapidly breaking up. Exposure June 12 
i ella. 
ees almost entirely palme 
Pare this wit own, the new filaments are aa 
