Generations , and General Cytology of the Uredineae . 327 
of Flemming’s weaker fluid diluted with an equal quantity of water. After 
fixing and washing, the material was brought up to the clearing fluid by the 
method of Overton ( 41 ). It was first placed in 10 °/ o glycerin, which was 
allowed to evaporate either in a warm place or in a desiccator over calcium 
chloride ; the glycerin was then removed with absolute alcohol and 
the material placed in a io°/ o solution of cedar oil in alcohol. After 
the alcohol had evaporated in a desiccator the material was obtained in 
cedar-wood oil without the least distortion of the delicate germ-tubes, 
and with far less trouble and risk than by the passage through various 
strengths of alcohol, and mixtures of alcohol and clearing fluid. The 
material can then either be treated by the method of fixing to the slide (see 
Blackman, 8), or by imbedding small teased pieces in hard paraffin very 
successful sections can then be made through the teleutospores and germ- 
tubes. By the latter method alone can the details of nuclear division 
be successfully studied. For staining the cell-walls of the hyphae a 
1 °/ o watery solution of Congo -red, either neutral or slightly alkaline, was 
found of great use, as it stains the walls of the hyphae without affecting 
the host-cells. 
I have to thank Miss H. C. I. Fraser for very considerable help in 
preparing material during the latter part of this work. 
TELEUTOSPORE AND PROMYCELIUM. 
Phragmidium violaceum. 
The peculiar nuclear cycle with its sudden transition in the aecidium, 
as described by Sapin-Troufify, was fully confirmed in the case of the two 
forms investigated. It will thus be convenient to start with the first stage 
of the series with single nuclei — the mature teleutospore — and then work 
by way of the spermogonia and aecidia to the series with paired nuclei, and 
after dealing with the uredospores end with the development of the teleuto- 
spores and the fusion of the two nuclei into one. 
Mature Teleutospore . The teleutospore of this form appears towards 
autumn, and is to be found in groups on the leaves which remain attached 
throughout the winter. It is a large structure consisting usually of four 
thick-walled cells, and a stalk which is enlarged below, this part of the 
stalk being capable of swelling up in water to a great extent (Fig. 1). 
The wall of the uppermost cell is provided with a rounded peg-like projec- 
tion of cell-wall substance which is sometimes perforated by a narrow canal 
connected with the cavity of the cell below. The whole spore is covered 
with a thin cuticular layer which is raised into numerous rounded bosses 
(Figs. 1 and 2). Each cell possesses a delicate endosporium, a continuous, 
thick mesosporium, and an outer exosporium, which is to be found only as 
