WHITE-PINE BLISTER RUST. 31 



GERMINATION OF THE PYCNOSPORES. 



Plowright states that pycnospores (spermatia) of some of the 

 Uredinales have been germinated in sugar solutions by Cornu and 

 himself (110). Brefeld (7) states that the spermatia of several rusts 

 have been germinated in culture solutions. Later Carleton (10) 

 stated that he had been able to germinate the pycnospores (sperma- 

 tia) in but a single instance. 



The spermatia of Uredo caeoma-nitens Schwein., budded sparingly on May 31, 1893, 

 after 24 hours in a dihite solution of honey, but would not germinate in water. 



Still later he said (11); 



Until recent years it was not supposed that the spermatia produced regular germ 

 tubes, but that the germination is always simply a process of budding. Dr. N. A. 

 Cobb and the \vriter have shown, however, that ordinary germ tubes are produced in 

 the germination of these spores as well as in the other spore forms * * *. Spermatia, 

 though germinating readily in water, will be found to do much better in a rather 

 dilute sugar solution, or perhaps still better in a solution of honey. 



Investigations were made in 1918 by York and Overholts/^ who 

 tested their germination in water and in various solutions of glucose, 

 cane sugar, dextrose, maltose, lactose, peptone, extract of macerated 

 Ribes leaves, and extract of macerated pine bark. Fresh pycnospores 

 gave no germination. Pycnospores subjected to the cold of an ordi- 

 nary refrigerator from 3 to 20 days gave degrees of germination 

 increasing with the length of time in cold up to 18 days. Germina- 

 tion occurred in 3, 5, and 6 per cent cane sugar and in 3, 6, and 10 

 per cent dextrose. The stronger dextrose solutions gave the best 

 results. No germination occurred in tap water in any case. 



SEASON OF PRODUCTION OF PYCNIAL SPOTS, DROPS, AND SCARS. 



The dark spots (PL II, fig. 2, h) which precede the exudation of the 

 pycnial drops may be found in the infected bark at all times of the 

 year. Records and observations made from 1909 to date furnish 

 definite data on the season of pycnial drop formation. (See Table V, 

 p. 72.) The pycnial drops are produced immediately after the 

 secial season; that is, from about June 20 until winter. The rusty- 

 brown scars left after the disappearance of the drops may be seen 

 at all times of the year on old cankers. On new infections the scars, 

 of course, do not appear until the drops have formed and disappeared. 

 All of these are positive symptoms of this disease in white pinQS. 



THE j^CIA AND /ECIOSPORES OF CRONARTIUM RIBICOLA. 



SEASON OF PRODUCTION OF THE ^CIA. 



The recia develop at varying dates in the same locality in dift'erent 

 years, according to the season. The locality, whether a warm or 

 cold exposure, at a low elevation or a high one, well to the south or 



'- York, H. n., and OverhoUs, L. O. The germination of t,he pycnospores of Cronartium ribicola. Seen 

 in manuscript. To be published in Phytoiiathology. 



