1917] BOURQUIN—ZYGNEMA 433 
The starch grains come to lie radially about the pyrenoid in 
the following manner. The plastid adds to them in such a way 
that they become cuneate in shape. In this manner they grow 
down between the starch grains already formed until they are of 
the same length as the large grains. The plastid then broadens 
them at the base until they become rectangular in shape. 
AGNES Scott CoLLEGE 
Decatur, GA. 
: LITERATURE CITED 
1. CuMILEwskyy, W., Uber Bau und Vermehrung der Pyrenoide bei einigen 
Algen. Bot. Centralb. 69: 277. 
- MERRIMAN, M. L., Nuclear division in Zygnema, Bot. Gaz. 41:43-51. 
1906. 
3. Meyer, Artuur, Uber der Krystalloiden der Trophoplasten und iiber die 
Chloroplasten der Angiospermen. Bot. Zeit. 41:489-498. 1883. 
i aig ig iiber die Starkekérner. Jena. 18 
: , Uber die Entwicklung der Chlorokérper und die 
Farbk6rper. Bot. ae 41:105-113, 121-131, 136-146, 153-160, 809-817. 
88 
uN 
uw 
DM 
a 
ty ~ 
PR 
> 
6. ———,, Untersuchungen iiber die Chlorophyllkérper und die ihnen homo- 
logen Gebilde. Jahrb. Wiss. Bot. 16:1-127. 
ScuMiTz, FR., erties zur Kentniss der Chrotaatophoren. Jahrb. Wiss. 
Bot. 15:1-175. 
TIMBERLAKE, H. ss Starck formation in Hydrodictyon utriculatum. Ann. 
Botany 15:619-634. root. 
9. SAMANOSS, S., Hydrodictyon africanum. Bort. GAZ. 55:72-79. 1913. 
Ps 
go 
EXPLANATION OF PLATE XXVII 
The drawings were made by the aid of the camera lucida, the magnification 
being X 1040. The abbreviations used are as follows: c, cytoplasm; 7, pyrenoid; 
n, nucleus; p, plastid; g, starch grain; #, starch grain growing in length toward 
center of plastid; /, starch grain growing broad at base; s, minute starch grain. 
Fie. 1. tical section of cell showing relation of cytoplasm, nucleus, 
and chromatophores, and showing ie chromatophores packed with large 
Starch grains radiating from pyreno: : 
Fic. 2.—Optical section of giana ca showing grains of varying width 
at base. 
Fic. 3. —Optical section of chromatophore showing grains of varying 
lengths and grains which vary in width of base as compared with width of 
outer edge. 
