WHITE-PINE BLISTER RUST. 67 



at Washington, D. C, showed that weevils, snails, slugs, and sow 

 bugs feed on the telia. The voided teliospores retained viability in 

 a few instances. This indicated that similar animals might be active 

 agents in the local distribution of these spores out of doors. Investi- 

 gations by Snell (127) in 1918 at Lewis, N. Y., showed that a number 

 of different types of insects feed on rusted leaves of Ribes bushes and 

 may serve as carriers of the sporidia directly from plant to plant, or 

 indirectly by the voided teliospores. Marshall, in 1917, found that 

 the moist sporidia allowed to dry on a feather are not easily dis- 

 lodged therefrom, either by wind or by brushing of the feather on 

 cloth. This suggests the possible carriage of sporidia by migrating 

 birds in the fall for long distances. Their very short life, as deter- 

 mined by York (see pp. 67-68), however, probably prevents their 

 causing infection of pines under these conditions. 



The remarks on the carriage of aeciospores by currents of air gen- 

 erated by fast-moving automobiles, Steam trains, and electric cars also 

 apply to the sporidia. (See p. 36.) 



GERMINATION OF THE SPORIDIA. 



Gravatt, Colley (20), and York, Overholts, and Taylor^'' found 

 that the sporidia germinate immediatel}^ in tap water under favor- 

 able conditions. They germinate like ordinary fungus conidia, by 

 pushing forth a germ tube which is relatively large. They are capable 

 of germination as soon as they reach full size, even though still 

 attached to the promycelium. The germ tube normally develops 

 until a mycelium is formed. In some cases the germ tube soon forms 

 a secondary sporidium which in turn may germinate. The viability 

 of the fresh sporidia is high, as many as 90 per cent germinating 

 within 24 hours. 



LONGEVITY OK THE SPORIDIA. 



The sporidia of Cronartium rihicola are so thin walled, and fragile 

 in character that it seems self-evident that they are short-lived spores. 

 This supposition has been proved to be correct by the work of York 

 and Overholts in the summer and autumn of 1918 and of York and 

 Taylor in 1919 (cited in Spaulding, 146). Colley (20) found in 1917 

 that fresh sporidia germinated readily in distilled-water cultures. 

 York, Overholts, and Taylor ''"' dried the sporidia on glass slides and 

 tested their viability after varying intervals. Very slight germina- 

 tion resulted after 10 minutes exposure by an open window at 66° F. 

 when light rain was falling. None survived when exposed to bright 

 sunlight for 10 minutes with a temperature of 77° F. Nor did they 

 survive when pieces of Ribes loaves bearing the telia and s]")ori(lia 

 were exposed to sunlight for 10 minutes at 85° F. and with a humidity 



«> York, H. H., Overholts, L. O., and Taylor, M. W. Op. cit. 



