Florida Agricultural Experiment Station


cently formed cracks in the bark will very likely be found to be
free from discoloration, while in those of longer standing the
bark will be found to exhibit a dark color on either side but not
necessarily extending into the cambium. In still older cracks the
discolored area will have enlarged and the bark may be dead
down to the wood. In some cases the dead patch of bark will be
found to be loose and springy, due to the accumulation of liquid
 g u m beneath i t.
 This is the result of
 v t t h e cambium, o r
 tios growing layer, form-
 Siing elements which
 degenerate into gum
 instead of forming
 normal woo d ele-
 ments. With the con-
 tinued development
 of the disease, addi-
 tional cracked, gum-
 ming areas appear in
 the bark and, eventu-
 ally, extensive areas
 become involved.
 In some cases
 where the gumming
 occurs i n isolated
 spots the gum flow
 may become checked
 a n d the ruptured
 places in the bark
 h e al over. In such
 cases, new bark
 forms under the old
 which dries out,
 hardens, and is
 Fig. 25.-Close-up view of portion of grape- forced up in irregu-
 fruit trunk affected with gummosis just lar partially detached
 above the bud union. Note copious exuda-
 tion of gum down center of trunk; also note scales o r narrow
 cracks in bark at left (indicated by arrows) strips. This exposes
 that probably will exude gum later.
 lig h t colored to
 brownish, resinous-looking scars to which the loosened bark re-