There is considerable variation among rose varieties in susceptibility
to mildew, and as a result of maturation, leaves of most
susceptible varieties become resistant to infection. The nature of
resistance has been sought in various studies involving environmental,
morphological, and physiological factors. An attempt was made in the
present investigation...
At the time of the eruptions of Lassen Peak in 1914-1915, an
area of vegetation along the east slope of the mountain approximately
1 1/4 miles wide and four miles long was destroyed. Except for a
few surviving trees, all vegetation was destroyed.
A study of the revegetation of this...
Three viruses were isolated from dahlias using a modification of
Yarwood's leaf-disc method of inoculation. Two of these isolates have
been reported previously in dahlias. In addition, a fourth virus was
isolated using a liquid-nitrogen transmission technique.
Dahlia virus isolate 1 possessed host range and thermal inactivation
properties similar to...
The vegetation of the Oregon coast is characterized by a
variety of stages of plant succession which are repeated widely
throughout the sand dune area. During the years from 1960 to 1963
the gradation of upland sand dune succession was studied on 48 plots
within a 150 mile section of...
Recent investigations indicate that several latent viruses of
apples exist in common commercial apple stocks, but these viruses
and their relationships are incompletely understood. This thesis
describes investigations of crab apples as indicators of latent viruses
of apples.
Eighty-eight varieties and species of crab apples were tested
as indicators of...