1 08 Butler . — A Study on Gummosis of Primus and Citrus , with 
I. INTRODUCTION. 
Review of Literature. 
The identity of the gum disease of Primus and Citrus , an identity 
implied in the title of this paper, has been, if not definitely proved, at least 
vouchsafed for by Savastano and Delacroix. According to Savastano the 
histology of gummosis in the Citrus is similar to that described by various 
authors for species of P run us and Citrus. He agrees with the histological 
characters of these diseases as they are given by Beijerinck, Comes, Briosi, 
Sorauer, Frank, and especially Trecul and Prillieux. Delacroix, on the 
other hand, observed some differences : starch, always present in the gumo- 
genetic tissues of Primus , is absent from the affected tissues of Citrus , and 
gummosis usually begins at the periphery of the gum parenchyma in the 
latter, instead of in the centre as in Prunus . Otherwise the histogenesis 
of the disease is the same in both genera. In other works on gummosis of 
the Citrus that I have consulted, the histology of the malady is not studied 
at sufficient length to warrant any conclusions regarding the validity of 
Savastano’s and Delacroix’s conclusions. For this reason it appeared to me 
that a reinvestigation of the development of gummosis in the Citrus could 
be profitably undertaken. 
Gummosis of Prunus, on the other hand, has been frequently studied, 
and it would appear, at first sight, that little remained to be discovered 
regarding this disease. A review of the most important memoirs that have 
appeared shows very clearly, however, that our knowledge is still imperfect, 
and that further studies on this important malady are necessary to elucidate 
doubtful and obscure points. 
Previously to i860, when Trecul’s observations on gummosis of the 
stone fruits appeared in the Comptes Rendus, no studies of any importance 
had been published on this malady. 
Trecul 1 believed that gummosis was induced by a variety of causes, 
all of which were instrumental in accumulating in the pathognomonic zone 
a superabundance of sap. The disease affected either the young wood 
in formation, or the more differentiated and lignified tissues behind it. 
In the embryonic wood cells the gum pockets were formed by resorption of 
the cells, and more especially in the regions where the vessels appeared to 
be laid down. The lacunae thus formed were filled with fluid containing the 
dissolved contents of the resorbed cells, the remnants of their cell walls, 
still in process of dissolution, together with entire cells broken free from the 
periphery of the gum cavities ; these latter cells sometimes enlarged con- 
siderably and divided transversely into several cells before being, in turn, 
1 Trecul, A . : Maladie de la gomme chez les cerisiers, les pruniers, les abricotiers, les aman- 
diers. Comptes Rendus, li, 186c, pp. 621-624. 
