filled with it. The starch disappears with the increase of these masses. 

 Savastaiio observed, even in seedlings, a production of gum centres at the 

 point where the young roots passed into the trunk and branches. I found 

 similar conditions in the sweet cherry, which externally showed no trace 

 of disease. 



Savastano found gummosis appearing also in the trunk and branches. 

 He found a substance in its gum which seems to be similar to "Olivile" 

 occurring in the gummosis of the olive. The gummosis of the trunk and 

 branches starts in the gum glands found even in the roots of saplings. Only 

 after the plants have become diseased with gummosis may the presence of 

 Rhizomorpha be proved which other investigators have considered the 

 causes of the disease. With the red discoloration of the walls, the paren- 

 chyma cells of the roots undergo a process of humi faction in which the 

 specific weight of the tissue becomes less and less because the organic 

 substances disappear. 



A later work by Savastano^ gives the results of comparative experi- 

 ments with specimens of Amygdalus Persica and Amygdalus communis, 

 Pntnus Cerasiis, P. domestica, P. inifitia, P. Mahaleh, and P. Armeniaca, 

 as well as Citrus Aurantium, C. Limonum, C. vulgaris and C. nobilis, and 

 also of Olca europaea afifected by gummosis. The results show that the 

 gummosis of the plants named has much in common with that of Ficus 

 Carica. In all, the formation of gum centres either takes place as a result 

 of injur}', or without any external cause. If the wound is overgrown 

 quickly and completely, the gum formed dries up, as a rule, into brittle 

 masses and remains uninjurious for the surrounding tissue. If, on the 

 other hand, moisture is present on the wounded places, the gum remains 

 soft and is easily carried over the surfaces surrounding the wounds, which 

 also succumb to gummosis. 



The Exudation of Manna. 



In many plants, instead of gum, a hard, clear substance containing 

 sugar comes from the bark of young trunks and branches, and is called 

 Manna in trade. The liquefaction product contains Mannit which, when 

 extracted with alcohol, can be obtained in fine white silky crystals, tasting 

 slightly sweet, and may also be formed artificially from different sugars. 

 Investigations of the Manna exudation were begun by Meyen-. According 

 to him, the large amounts of Manna, which come from Italy, are obtained 

 artificially from a kind of alder, the Manna Alder, by making incisions in 

 the bark toward the end of July. From these incisions the Manna flows 

 gradually as a thick, sweetish juice, hardening in the air. 



Resinosis. 

 The exudation of resin (resinosis) is for conifers what exudation of 

 gum, is for the Amygdalaceae and the Manna exudation for the Oleaceae. 



1 Gummose caulinaire dans les Aurantiacees, Amygdalees, le Figuier, I'Olivier et 

 noircissement du Noyer. Compt. rend. I, Deceln-e, ISSl. Reprint. 



2 l^flanzenpatliulogie, p. 228. 



