No. 466.] STUDIES ON PLANT CELL.— VII. 707 
Olive's results in studies on the Cyanophycez it does not 
seem unreasonable to hope that more accurate staining of very 
thin sections will bring the peculiarities of these accounts into 
harmony with mitotic phenomena of higher forms. 
The accounts of conjugation in yeasts (Barker, :or and 
Guilliermond, :03) which were discussed under * Asexual Cell 
Unions and Nuclear Fusions" in Section IV give no additional. 
information on the essential structure of the yeast cell. 
2. COMPARISONS OF THE STRUCTURE OF SOME HIGHER TYPES 
OF PLANT CELL wiTH SiMPLER CONDITIONS. 
Some of the most fruitful and interesting fields of investiga- 
tion in cell structure are likely to be in those border groups 
between the very simplest conditions of the lower alga and 
fungi and the higher regions where the nucleus and processes of 
mitosis have clearly the essential features which are generally 
ascribed to this structure and its activities. At present the gap 
seems very great between the simple conditions of the Schizo- 
phyta and the groups of alge and fungi on the next higher 
general level. But as a matter of fact we know almost noth- 
ing of the nuclear structure in the lowest groups of the Chloro- 
phyceze, z. e., among the simplest of the unicellular green algae. 
It is rather remarkable that this region should have been 
so neglected. | 
The Nucleus.— Comparative studies on the nucleus naturally 
treat chiefly of the chromosomes and nucleolus. One of the 
most interesting features of more recent research on the nucleus 
has been the steady accumulation of evidence indicating that the 
nucleolus holds a very important relation to the chromatin con- 
tent. There are types among the lower algae in which the whole 
or a greater part of the chromatin is gathered into a dense nu- 
cleolar body in the resting nucleus.  Spirogyra is the best 
known illustration of this condition and has been studied by 
several investigators. Similar phenomena have been reported 
by myself in Corallina (Davis, '98), by Golenkin ('99) for 
Spheeroplea, and by Wolfe (:04) for Nemalion. Some nuclei, 
however, particularly in the higher plants have nucleoli whose 
