igi2] CURRENT LITERATURE 173 



no results unless the tip is present. The meristem in Lupinus, the form used, 

 is starch free, consequently this interpretation which seems to agree well 

 with all facts observed is opposed to the starch statolith theory. — William 

 Crocker. 



Gummosis. — Sorauer, 11 in two extensive papers, discusses gum-flow in 



■ 



the cherry and related phenomena in some other trees. He concludes that the 

 tendency to gummy degeneration is latent in the cherry tree, and that stimuli 

 such as frost and wounds only accentuate a natural tendency. Individual 

 cells in the pith and bast, which in perfectly normal twigs of various 

 trees show swelling of the walls and discoloration and degeneration of 

 the contents, exhibit the primary evidences of the tendency to gummosis. 

 Through variations in growth that may be regarded as normal, such as unusual 

 breadth of the medullary rays, or through variations in nutrition affecting 

 turgor, or through wounds, effects of frost, etc., the tension relations between 

 pith and wood, and between wood and bark, are frequently greatly altered, 

 resulting in release of pressure at certain points. At these points, islands of 

 parenchymatic cells are regularly formed, among and in place of the normal 

 prosenchymatic cells. This is a common phenomenon in many trees, without 

 gummosis following; but in the cherry such islands of cells #re the usual foci 

 of gummy degeneration. They are particularly numerous in the wood formed 

 by late fall growth; consequently different parts of the same branch or tree 

 vary enormously in the tendency to gummosis. 



Cells having the tendency to gummosis are deficient in starch, thin-walled, 

 with heavy deposits of tannin and phloroglucin ; in a word, they 'are cells which 

 fail to mature. The cause of degeneration may be regarded as an excess of 

 enzymes; degeneration in the individual cell starts in the cell contents, and 

 extends to the secondary membrane, which swells and furnishes the chief 

 material for the gum. As the gummosis extends to adjacent cells the order 

 is of course reversed, the intercellular substance being first attacked, the cell 

 contents last. 



The bulk of these papers is devoted to a minute description of the histology 

 and microchemical reactions of a great quantity of material illustrating various 

 aspects of the gummosis problem. In addition to various species and varieties 

 of Primus, the following species are studied: Corylus avellana, Pinus Laricio, P. 

 silvestris, Fagus silvatica, Fraxinus excelsior, F. Ornus, Syringa vulgaris, Cytisus 

 Laburnum, Tilia sp., Ampclopsis sp., Platanus sp., and the pear. Scant atten- 

 tion is given to the work of previous investigators. These papers are of great 



deduct 



affi 



11 Sorauer, Paul, Untersuchungen fiber Gummifluss und Frostwirkungen bei 

 Kirschbaumen. Landwirtsch. Jahrb. 39:259-297. pis. 5. 1910; and 41:131-162. 

 pis. 2. 191 1. 



