210 
Journal of Agricultural Research 
Vol. XXV, No. S 
fined to the leaves in localized areas. The gametophytic hyphae become 
established in the perennial plant structures, from which they invade the 
new canes throughout their length and finally take part in the formation 
of aecidiospores. Newcombe ( 8 ) and Clinton (j) have given practically 
the only accounts which deal with the mycelium and haustoria of the 
orange-rusts in the host tissues. Both authors used the infected black¬ 
berry as the subject of investigation. Newcombe did not study sections 
of the roots, confining his attention to 16 cm. of an infected blackberry 
cane. He discovered that the bulk of the mycelium was to be found in 
the pith of the stem, noting hyphae in a medullary ray at one place. 
Clinton found mycelium in the fundamental tissue of the growing point, 
and although in old stems the hyphae were confined to the pith, they 
sometimes occur in the cortex and in the phloem of the bundles in young 
and growing shoots. He states that— 
mycelial threads are present from the upper parts of the roots running through the 
stem into the uppermost leaves showing signs of infection * * *. Frequently 
plants are found in which the new shoots are affected but the old ones are free. In 
Fig. i.— At the left, growth of shoot H from root runner. A, in April. At the right, same plant in Octo¬ 
ber; B, root crown; small central pith would be found at E; horizontal roots, C, which happened to 
develop in this case do not ordinarily appear the first year. 
such case the mycelium is found in the former only * * *. Sections of roots, ex* 
cept in the neighborhood of the merging of root and stem, do not show the mycelium. 
Intercellular hyphae without septa or nuclei and the simpler types of 
haustoria are figured. 
MYCELIUM IN THE BLACKBERRY 
Clinton’s account of the distribution of the mycelium is correct in 
general if applied to blackberries which have been infected for at least 
two years, except when he states that the roots of an infected plant do 
not show any mycelium other than in the transition zone where root and 
stem join. The writer has found that hyphae invade the roots of the 
blackberry very extensively, a fact which accounts for the rapid spread 
of the parasite to new shoots which rise from the roots. The blackberry 
forms a few large roots, some of them becoming runners which by bud¬ 
ding give rise to new plants at some distance from the parent. These 
runners are true roots morphologically, their structure being the same as 
that of the ordinary root of the blackberry. If one carefully uproots rusted 
