456 
Journal of Agricultural Research 
Vol. XXVII, No. 7 
The nature of this “after-ripening” period is not known, although 
it generally is assumed to be analogous to the after-ripening period of 
the seeds of many higher plants. It is possible that with many fungi 
this period is necessary in order to enable certain changes to take place 
in the protoplasmic contents of the spore or spore wall. 
In experiments designed to hasten the after-ripening process in telio- 
spores of Puccinia graminis, Thiel and Weiss (48) secured germination 
of the spores after preliminary treatment with dilute citric acid, several 
months before germination could be obtained by ordinary methods. 
They report the work of Crocker, Eckerson, Denny, and others on after¬ 
ripening in seeds and permeability of seed coats, in which it has been 
shown that germination may be delayed until certain definite physiologic 
changes have taken place in the embryo, or, in other cases, until the 
seed coats become permeable to water and oxygen. 
Thiel and Weiss state that the stimulus to germination of teliospores 
apparently was not the result of increased permeability of the spore wall, 
but rather that the citric acid appeared to function as a specific activator 
of the protoplasm. However, similar treatment of spores of Urocystis 
tritici did not materially increase the amount of germination. 
Harrington (14) has discussed the effect of artificially drying by 
heat in hastening the germination of seeds of various cereals which had 
not after-ripened. Many investigators have mentioned the beneficial 
effects of such a procedure. A somewhat similar effect after drying in 
vacuo or over sulphuric acid also has been observed. 
While studying the effect of temperature and relative humidity on 
the viability of the spores of Urocystis tritici , the writer obtained some 
interesting results on the effect of drying fresh spores which had been 
produced under greenhouse conditions. 
Certain infected leaves were closely watched for the change of color 
in lesions. Two days after the lesions had changed from a whitish gray 
to a dull, leaden-black color, the infected leaf was removed, cut into 
strips about 1 cm. in length, and then dried for 48 hours at room temper¬ 
ature (18 0 to 22 0 C.) in a dessicator over concentrated sulphuric acid. 
At the end of this period the spores were shaken out from the leaf section 
onto the surface of a few cubic centimeters of distilled water, in the 
manner already referred to, and after three days small quantities of 
young wheat tissue were added. Eighteen hours later, from 60 to 70 
per cent of the spores had germinated. In control dishes, spores obtained 
from the fresh, undried lesions failed to germinate on the addition of 
similar amounts of young tissue. Four weeks later, when the infected 
plants were removed, the sori in the remaining leaves were still unruptured. 
It is not known whether there was any effect on the internal composi¬ 
tion of the spores or whether the treatment merely acted on the spore 
envelope, possibly removing certain substances from its surface and 
thereby facilitating the ingress of water necessary for germination. 
However, it apparently had the effect of shortening the maturation 
period, which previously had been considered as essential before the 
spores would germinate. 
It is thus evident that caution should be exercised in stating that 
certain definite maturation periods are necessary unless the environ¬ 
mental conditions are known. Attention is drawn to this fact elsewhere 
in this paper in a discussion of the effect of chemical stimulants on the 
spore. 
