Florida Agricultural Experiment Station


tain their food material chiefly from the air, or dead, function-
less tissues of the bark on which they grow. In addition to grow-
ing on the trunks and branches of citrus trees, they may be found
growing on fence posts, rocks, and other inanimate objects. In
 groves, lichens a r e
 more apt to be abun-
 dant in damp, shady
 situations a n d are
 frequently conspicu-
 ous on old, neglected,
 and run-down trees.
 They thrive in the
 moist, humid climate
 of Florida.
 There are many
 varieties of lichens.
 A very common form
 is a grayish-green,
 paper like growth
 that occurs on the
 bark. This growth
 may vary from small
 spots or patches to
 areas so continuous
 and extensive as to
 cover trunks a n d
 1 i m b s completely
 (Fig. 96). The edges
 are usually lobed and
 c u r 1 upward. An-
 cther lichen appears
 in the form of a
 round, pinkish-white
 area, adhering close-
 ly to the bark. Still
 another form ap-
 pears as small, black
 dots on a white,
 Fig. 96.-Lichens on the trunks of orange trees.
 indefinitely outlined
background. The leaf-inhabiting lichens are less common and
appear as more or less numerous, small, rounded, grayish spots
closely resembling algal spots (Fig. 97).