WHITE-PIISrE BLISTEL RUST. 



13 



1904, the pines were examined. At that time some of the new shoots 

 bore abnormal leaves of a juvenile type singly, instead of in fives. 

 The new twigs were abnormally pale in color. Man}^ of the leaves 

 of the growth of the previous year were spotted with yellow through 

 their entire thickness. These yellow spots were especially plentiful 

 near the base of the leaves. Microscopic examination showed abun- 

 dant mycelium to be present in the yellow areas. Later pycnia devel- 

 oned on the twigs near the bases of the spotted leaves. 



Fig. 10. — Outline map of the northeastern part of the United States, showing (by black dots and cross 

 hatching) the known distribution of white-pine bUster rust in North America to and including 1916. 



In 1914, Tubeuf (174) inoculated trees of Pinus strohus, P. lam- 

 hertiana, P. cembra, P. cembroides, P. excelsa, P. pence, P. parviflora, 

 P. jiexilis, and P. 7nontezumae with sporidia of Cronartiiim ribicola 

 under controlled conditions. In 1917, secia were produced on some 

 of the P. strohvs. Yellow spots were produced on the leaves of P. 

 lamhertiana, but no further development of the fungus occurred. 

 Spots which were doubtfully caused hy the fungus were noted on P. 

 cembroides. No other species became infected. Infections were 

 produced directly on the juvenile leaves, on mature leaves, and 

 through the epidermis of the lengthening buds of the young shoots. 



In North America, the waiter seems to have been the first to 

 moculate successfully young Pinus strobus trees with sporidia (133, 

 134). The inoculations were made both with and without wounds 

 in the young bark, telial columns being used for inoculum. Pycnial 

 drops were proiluoed by one tree unwoundcd and by one which was 



