811 



Conlmry to what ini^»iit be expected the i)heiionieiion is the more 

 obvious iis I he trees tire belter fed and more vigoi-ons. In s})ec'imens 

 on sandv m'l'ounds i( can only be obser\ed widi the microscope. 



As gummosis is the eHect of a wound slimuhis, it is of import- 

 ance that this process also takes place in the normal development 

 of the healthy plant. The subject is moreover of practical interest. 

 All the chief facts I'elating- to gum formation can almost unchanged 

 be applied to the production of gums in general, of gum resins, 

 and of resins, among which are substances of great medical and 

 technical value. As the study of the iidluence of parasitism has made 

 it j>ossible to {>roduce gum, and no doubt many of the other sub- 

 stances mentioned, in a more rational way than has been done till 

 now, a short review of the whole subject seems not supertluous. 



Woïüid stiimdus as cause of (/ummosis. Poisoning, and 

 parasitism also causes of this stimulus. 



Gummosis in the Amygdalaceae is a process of cytolysis, whereby 

 young cells, freshly sprung from cambium or procambium, and 

 sometimes also young parenchyma, are more or less completely 

 dissolved and converted into canals or intercellular spaces, filled 

 with gum. In dissolved parenchymatous tissues usually remains of 

 not wholly disappeared cell walls are found; the gum of tlie phloem 

 bundles is more homogeneous, but always the microsomes of the 

 dissolved protoplasm are found. The nitrogen of the gum springs 

 from the dissolved pi-otoplasm. 



Formerly we proved ^) that by such different causes as poisoning', 

 parasitism and mechanical wounding gummosis may be experimentally 



almond Amygdalus communis var. amygdalo-persica. At present the name 

 Amygdalus persicoides (Koch, Seringe, Zabelj is also used, as in the Hortus 

 of the University of Leiden. The opinion that it is a hybrid is not sufficiently 

 founded. When grown from seed the tree seems constant (see Meijer's Gonver- 

 salionslexikon. Articles "Mandef" Bd. 11. p. 853 and "Pfirsich" Bd. 13, p. 782, 1896) 

 and identic with tlie "English almond", of which Darwin reproduces a stone 

 (Domestication, 2nd Ed., Vol. 1, p. 858, 1875). The fruit is fleshy and bursts 

 open, the kernel is edil)le, not bitter. At Delft sowing experiments have been 

 going on a long time already, but under unfavourable circumstances. The root 

 cannot resist the winter temperature of the soil, hence, grafting on the plumtree 

 is required. 



1) M. W. Beijerinck et A. Rant. Excitation par traumatisme et parasitisme, et 

 écoulement gommeux chez les Am.ygdalées. Archives Néerlandaises, Sér. 2, T. II, 

 Pag. 184, 1905. — Gentralblatt f. Bakteriologie, 2te Abt., Bd. 15, Pag. 366, 

 1905. — A. Rant : De Gummosis der Amygdalaceae. Dissertatie Amsterdam, 

 BüSSY, 1906. 



