196 G. S. West and Clara B. Starkey. 
acid, and (H gm. of iodine. In this solution the stain became 
fixed and the filaments were then transferred to absolute alcohol; 
finally they were passed into xylol and mounted in Canada balsam. 
During the process the oil-globules were dissolved out and the 
cytological details could he clearly seen. The cell-wall was stained 
a pale blue-green, the general cytoplasm and the chloroplast red, 
the pyreno-crystal deep red and the starch envelope of each pyrenoid 
pink. A deeper stained network could be very clearly seen in the 
chloroplast. The chromatin granules in the nucleus were stained 
deep blue-green. 
With Delafield’s haematoxylin, and with iron-alum and 
Heidenhain’s haematoxylin, the network of the chloroplast, 
the pyrenoids and the nucleus were all brought out distinctly. 
In the diagnosis of the genus Zygogonium given by Wille in 
1897 1 he states that the cells possess two axile irregular chloroplasts 
each with one pyrenoid. In his revision of the Conjugate in 1909 2 
this statement is changed to one axile chloroplast with one pyrenoid. 
Bohlin 3 has also made some comments upon the chromatophore of 
Zygogonium ericetorum. In specimens collected in the Azores, he 
found that the general cell-contents had much in common with the 
normal condition found in Mougeotia, and that each cell possessed 
a band-like chloroplast with two pyrenoids. 
The principal alga which of late years has found a place in the 
supposed genus Zygogonium is Z. ericetorum Kiitz., an alga which is 
widely distributed almost all over the world. An examination of 
British material of this species, from various localities, and also 
sundry foreign examples, shows that the previous accounts of the 
cytology of this alga are far from accurate. 
The chloroplast is large and axile, with a variable and most 
irregular outline. It is often constricted in the middle, sometimes 
very deeply, and in some cases it is twisted at the constriction. It 
contains two large pyrenoids, one in each half (consult Figs. 1 and 
2). Sometimes in the actively growing filaments the chloroplast is 
completely constricted, so that there are two chloroplasts in each 
cell. Very occasionally, in cultures, chloroplasts have been seen 
with only one pyrenoid, or even destitute of pyrenoids, and on very 
1 N. Wille in Engler and Prantl, Naturliche Pflanzenfamilien, I Teil, 
II Abteilung, 1897, p. 20. 
8 N. Wille in Engler and Prantl, Natur. Pflanzenfam., Nachtrage zu 
I Teil, Abteilung 2, 1909. 
8 K. Bohlin, Etude sur la Flore algologique d’eau douce des A<;ores Bih 
till K. Sv. Vet.-Akad. Handl. Bd. 27, Afd. Ill, No. 4, 1901, p. 51, t. 1, f. 3. 
