Urocystis Cepulae. T. Whitehead. 67 
extreme impermeability of the central spore wall. After pro- 
longed treatment the vesicles separate in the form of round 
discs. 
Viability of Chlamydospores. No useful information based 
upon observations in this country is available, but in the United 
States the period during which spores remain viable is often 
given as at least twenty-five years and in a recent text-book (4) 
it is stated that there is no evidence of infected land \ ever be- 
coming clean. 
Germination of Chlamydospore. The germination of the spore 
ball has only been observed under the artificial conditions of 
the laboratory. In nature we may assume that a resting period 
after maturation is a necessary preliminary to germination. All 
attempts by the writer to induce fresh spores from the living 
leaf to germinate have failed, though Thaxter succeeded in 
germinating them in onion juice. After drying for about a 
month the spores were germinated with difficulty by first im- 
mersing the leaves in a freezing mixture at — 25° C. for twenty- 
four hours. When, however, spores which had been air dried 
for some sixteen months were used, germination was effected 
without the preliminary freezing. The spores were obtained in 
a surprisingly pure condition from the leaves, but the pre- 
caution was adopted of immersing the fissured leaf in o-1 % 
mercuric chloride for five minutes and then washing in sterilised 
distilled water before preparing hanging drops in sterile van 
Tiegham cells. Occasionally circular or pear-shaped resting 
spores of an undetermined fungus were present in the hanging 
drops and a few of them germinated, but they in no way 
obscured the observations on the germination of Urocystis. 
On germinating, one or rarely two germ tubes or promycelia 
penetrate the spore wall between the sterile cells. Germination 
in water is slow and the promycelium ceases to grow after 
attaining a length of some 40-50. Minute ovate sporidia are 
developed laterally upon the promycelium. 
In onion juice, germination is much more rapid and the 
germinal hyphae are much stouter. They branch and anasto- 
mose repeatedly so that under favourable conditions a mycelial 
plate some 0-25 mm. in radius may be formed in forty-eight 
hours. Sporidia much larger (7:4 x 3°5 «) than those developed 
in water are produced laterally and sometimes occur super- 
imposed in pairs. Thaxter states that in none of his cultures 
did any yeast formation take place as described in other species 
by Brefeld. In the present investigation, however, a hanging 
drop which had partially dried up was again flooded with onion 
juice upon which the sporidia separated from the hyphae and 
commenced to bud freely. A comparison of figs. 4 and 5 which 
5—2 
