3 H Carter . — Studies on the Chloroplasts of Desmids. IV . 
mally a correspondingly three or five lobed chloroplast, the latter enters the 
new semi-cell from the old one as a three or five lobed mass (Figs. 49 and 55). 
Thus the definite form of the chloroplast is retained as far as possible during 
the process of budding, and, as seen in Fig. 55, the five-lobed form of the 
chloroplast is visible in the young semi-cells of Staurastrum Brasiliense , 
Nordst., var. Lnndeltii , West, at a very early stage, long before the 
characteristic shape of the cell-wall is apparent. 
The nucleus of the cell is usually pushed to one side by the ingrowing 
chloroplast, especially where the latter is a single central one. In many 
cases it is very difficult, even in stained specimens, to distinguish the nucleus 
in newly divided individuals, in which the two halves of the chloroplast are 
not yet severed, but it can frequently be seen a little to one side (Figs. 49, 
54, 56, 57, and 60). Occasionally it is carried away to some considerable 
distance into the new semi-cell by the inrushing celbcontents, but whether 
such individuals survive in the end is doubtful. 
The simple chloroplasts of the smaller species of Euastrum and 
Cosmarium offer no striking phenomena during cell-division. As in C. sub- 
tumidum , the single central pyrenoid constricts to form two during the 
process (Fig. 54). In the very numerous species of Cosmarium containing 
two chloroplasts in a semi-cell, each with one point of pyrenoid formation, 
the budding of the chloroplasts has already been figured by de Bary ( 1858 ) 
as typified by C. Botrytis . Each of the two chloroplasts bud into the new 
semi-cell through the isthmus, the pyrenoid of each meanwhile constricting 
to form two. The process is identical in Euastrum verrucosum , Ehrenb., 
and also in those species of Xanthidium having a similar chloroplast 
structure. 
Where the axile chloroplast has more than one point of pyrenoid for- 
mation, as, for example, in Staurastrum anatinum , in which the cells, 
triangular in the end view, have typically one pyrenoid in each angle, all 
three pyrenoids constrict as the chloroplast projects as a trilobed mass into 
the young semi-cell (Fig, 58), 
In the case of axile chloroplasts containing numerous scattered pyrenoids, 
e. g. Tetmemorus , Micrasterias , and Staurastrum Brasiliense , a number of 
pyrenoids are carried into the young semi-cell by the budding chloroplast 
(Figs. 56 and 60), and they do not conspicuously increase in number during 
the process. 
With parietal chloroplasts, each one buds into the young semi-cell soon 
after its formation. Where each parietal plate contains a single pyrenoid, 
as in many species of Xanthidium , this constricts as the chromatophore 
projects through the isthmus, just as in the case of axile chloroplasts con- 
taining typically one pyrenoid ; but if the pyrenoids are numerous and 
scattered, as in X. armatum , (Breb.) Rabenh., a number of these pass into 
the new semi-cell along with the ingrowing chromatophore (Fig. 59), 
