AN ANATOMICAL STUDY OF GYMNOSPORANGIUM 
GALLS 
Alban Stewart 
GYMNOSPORANGIUM JUNIPERI-VIRGINIANAE ON JUNIPERUS VIRGINIANA 
The common "cedar apple" on Juniperus virginiana L., caused by 
Gymnosporangium juniperi-virginianae Schw., is one of our most 
common galls on coniferous plants. While the organism that causes 
this gall has been widely studied, but little work has been done on the 
changes brought about in the tissues of the host through the activities 
of this parasite, and the results obtained are contradictory. 
Sanford (8) was the first one to investigate the anatomy of the 
cedar apple caused by G. juniperi-virginianae. He considers the gall 
to be formed by an abnormal growth of leaf tissue, which carries the 
apex of the leaf up as the gall develops, and pushes the branch bearing 
it to one side until the gall appears to be terminal. He further states 
that the vascular system enters the knot as one single bundle, given 
off from the vascular bundle of the branch of the tree, and further, 
that as the knot increases in size the vascular bundle develops rapidly 
until it appears like the vascular system of a branch. 
Wornle (ii) who has done more work than any other investigator 
on the anatomy of Gymnosporangium galls, considers that the gall 
arises from a swelling of the stem induced by the fungus, that leaves 
may also enter into its composition, and, if dormant buds are en- 
countered, they also may be stimulated to development. 
Kern (6), who probably bases his statement on the work of Sanford, 
gives the cedar apple as an example of a gall originating in the leaves. 
Engler and Prantl (4), on the other hand, describe both G. juniperi- 
virginianae and G. glohosum as causing woody galls on Juniperus 
virginiana. 
Heald (5, pi. 10) has recently figured very young galls of this 
kind as arising near the axils of the leaves, and Coons (i, figs, i and 5) 
has figured galls some of which appear to be axillary in origin, and 
others arise from the upper surface of the leaf. 
These rather conflicting statements in regard to the morphology 
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