288 DopGE: STUDIES IN GENUS GYMNOSPORANGIUM 
not appear until the second year. All of the plants that were 
inoculated became so heavily infected that by 1918 many of the 
branches had been killed. Those plants that became infected 
without inoculation through being exposed near hawthorns bearing 
aecidia bore only a few sori in 1917 and had about twice as many 
in 1918. The invasion of new regions of the host by the mycelium 
TABLE I 
INOCULATION OF Juniperus virginiana WITH AECIDIOSPORES OF G. clavipes 
Plants inoculated August 1, 1915 Ced — d Sg Sahar — _— 
No. Results, 1916 | Results, 1917 No. Results, 1916 | Results, 1917 
401 | — | +, many sori | 405 - | +, 6 sori 
i ad Blea See Bate eae 407 = 
403 hae +, se “cc 408 wre cigs 
4I2 +, II sori ee 4 411 _ - 
415 +, 30 sori mk eel fe 938 — _ 
416 ‘+, I sorus “hy 2 413 - _ 
414 _ - 
417 - _ 
418 — +, 2 sori 
590 cm aap 
591 ce - 
594 as =< 
609 - _ 
is not very rapid. It has, however, completely connected spaces 
between most of the groups of sori that were evident on the plants 
in 1917. In some cases small witches’ brooms have been formed, 
and spindle-shaped swellings are beginning to appear on some of 
the larger branches and main stems. 
GYMNOSPORANGIUM MACROPUS 
The life histories of the two ‘‘cedar apple” rusts have become 
fairly well understood through field observations made by many 
investigators of the gymnosporangial stages, and by cultures of the 
rusts on their aecidial hosts. 
The cedar plants used in this work were obtained at Cold 
Spring Harbor, New York, February 1,1914. Some of them bore 
a few galls of G. macropus and G. globosum. Spores from these 
galls were used to infect seedling apples and hawthorns. The 
galls were marked with tags for further observation. The cedars 
were carefully inspected during the summer of 1914 and until 
