150 
junktor, Zwischen-zelle) between the conidia in 
species of Penicillwm are widely scattered through 
the literature. This was figured by Strasburger 
in ‘‘Zellbildung und Zelltheilung’’ (1879) and 
Teappears in the latest discussion of the group by 
Westling (1911). The appearances described under 
these names are easily seen and commonly but by 
no means uniformly found in certain species. To 
discuss this the usual method of conidial forma- 
tion must be briefly described. The spore-bearing 
cell (sterigma, basidium, conidiiferous cell) has a 
definite permanent length of fairly uniform diam- 
eter, then tapers into a tube of smaller diameter 
from which the conidia are abstracted. This fer- 
tile tube elongates rapidly during the growing 
period. The nucleus of the cell divides, one 
daughter nucleus migrates to the tip of the tube, 
a wall then cuts the new cell from the old. The 
newly formed conidium in every species so far 
carefully studied is cylindrical, and more or less 
quickly swells to assume the globose or elliptical 
form characteristic of the particular species. The 
cylindrical form is lost so quickly that many 
preparations will not show such conidia, especially 
where growth conditions are not especially favor- 
able. Similarly the tube may be very short or 
2 to 3m in length in the same preparation. As 
the conidia swell from the cylindrical to the ellip- 
tical or globose form the appearance described as 
a connective is obtained when the primary wall of 
the original tube fails to follow the change in 
form and leaves an open space between itself and 
the new walls of the adjacent conidia in the chain. 
This appearance is by no means uniform in any 
species examined, but admits of the same explana- 
tion in every case seen. Nuclei have been fixed 
and stained in but few of these forms. 
Perennial Gametophytic and Sporophytic Genera- 
tions in Puccinia obtegens (Lk.) Tul.: Epear 
W. OLIVE, South Dakota State College of Agri- 
culture and Mechanic Arts. 
This brachyform of rust, better known under 
the name of P. suaveolens, grows at Brookings on 
an European variety of Canada thistle. As de- 
scribed by Rostrup and others, it is said to possess 
two distinet generations: one resulting from a 
general infection throughout the whole plant, in 
which the characteristic, sweet-smelling pycnidia 
are shortly followed by large, confluent sori of 
uredospores, among which are later developed a 
few teleutospores; and, second, a strictly local in- 
fection, in which only uredo- and teleutospores are 
produced and borne in small, scattered sori. 
SCIENCE 
[N.S. Vou. XXXV. No. 891 
Some preliminary cytological investigations of 
the so-called first generation show that both uni- 
nucleated gametophytic and binucleated sporo- 
phytic mycelia ramify together throughout the 
infected plants. The uninucleated mycelium pro- 
duces the pycnidia; and is present also at the base 
of the uredo-sori. But the binucleated mycelium 
also invades the uredo-sori and these sporophytie 
hyphe alone apparently produce the uredospores, 
which therefore should be regarded as secondary in 
their nature. Primary uredospores, produced by 
sexual fusions, were not observed. Teleutospores 
also arose from the same sporophytie mycelium. 
The general infection of the Canada thistle is 
therefore due to the growth of two generations: 
a mixture of gametophytic as well as sporophytic 
mycelia; and the evidence appears to show fur- 
ther that both uninucleate and binucleate mycelia 
winter-over together in this mingled state in the 
underground parts of the plant. 
A Revision of the North American Species of 
Puccina on Carex: FRANK D. KERN and Mary 
A. FircH, Purdue University. 
Although there has been an accumulation of 
considerable information concerning the North 
American sedge rusts most mycologists have re- 
garded this group as especially difficult. This is 
perhaps due to the fact that the telia do not 
usually present diagnostic characters. In the 
separation of these species it has been necessary 
to look for other features, and, as has been the 
case in several other groups of the rusts, it has 
been found that the urediniospores have furnished 
especially good characters. The ecial connections 
as brought to light by cultures are also important. 
The presence of amphispores in some of these 
species and the splitting of other species into 
races lend biological interest to these studies. 
About twenty-five species of Puccinia on Carex 
can be recognized in North America, the majority 
being endemic. About three fifths of these have 
had their life-histories worked out. 
Cultures of Uredinee in 1911: J. C. ARTHUR, 
Purdue University. 
The thirteenth year of culture work with plant 
rusts gave an unusual number of failures, largely 
ascribable to the unseasonable hot weather. Of 
the 193 available collections with resting spores, 
mostly on grasses and sedges, only 37 germinated, 
as proved by about 700 drop-culture tests. Out of 
the small number 14 infections were obtained, with 
143 sowings. In addition to these 17 infections 
