200 Pflanzenkrankheiten. — Lichenes. — Pteridoph^nen. 



Sorauer, P., Einige Experimente zum Studium der 

 Frostwirkungen auf die Obstbäume. (Die Natur- 

 wissenschaften. I. p. 1055—58, 1094—97. 5 Fig. 1913.) 



Verf. schildert zunächst die Entstehung der durch starke Käl- 

 tegrade verursachten Frostspalten an Wald- und Obstbäumen 

 mit ihrer Heilungsform den Frostleisten und geht dann zur Be- 

 schreibung der Krebswunden, namentlich des offenen Krebses 

 der Apfelbäume über. Durch künstliche Gefrierversuche konnten 

 kleinste Risswunden in der Rinde von Apfelzweigen hervorgebracht 

 werden, die äusserst schnell durch Ueberwallung geschlossen wur- 

 den und mit den ersten Anfängen der Krebswunden vollkommen 

 übereinstimmten. Bei Birnbäumen konnte durch künstUche Kälte 

 Gelblaubigkeit oder Bleichsucht erzeugt werden. Die Wirkungen 

 der Spätfröste lassen sich in gewissem Grade durch direkte Schutz- 

 mittel, wie z.B. Räucherung der Wein- oder Obstanlagen, abschwä- 

 chen, wichtiger aber sind Vorbeugungsmassregeln, welche der durch 

 Düngung und Kulturschnitt gesteigerten Frostempfindlichkeit der 

 Obstbäume entgegenwirken. H. Detmann, 



Paulson, R. and P. G. Thompson. Report of Lichens of 

 Epping Forest (Second Paper). (The Essex Naturalist. XVII. 

 p. 90—104. 1912—1913.) 



The authors find that there are at present 109 species of lichens 

 in the district as compared with Crombie's 85 (in 1883). They dis- 

 cuss the possibility of lichens remaining in an indistinguishable 

 leprow State during the prevalence of unfavourable conditions and 

 their reappearance as specifically distinct plants when the latter 

 become less adverse. They then describe the more important plant 

 associations of the Epping Forest, as those of the base heath, wet 

 heath, trees, living and decaying, old brick walls. tombstones, and 

 even old leather and dry rabbit düng. The aspect preferred by 

 certain lichens ist next dealt with, and a few notes are added con- 

 cerning the probable extent of the fruiting periods, the rate of 

 growth of some lichens and also their ennemies. The paper con- 

 ducts a list of 63 lichens which added to the J6 of the first paper 

 makes up the total of 109. O. V. Darbishire. 



Allison, H. E., On the Vascular Anatom v of the Rhizome 

 of Platycerium. (New Phytol. XII. Nos. 9 a. 10. p. 311—321. 5. fig. 

 1913.) 



Platycerium alcicorne has a dorsiventral rhizome bearing on its 

 lower side a number of roots and on its upper side two kinds of 

 leaves, nest leaves alternating with foliage leaves. The axial vascular 

 System is a perforated dictyostele, each meristele consisting of 

 xylem, mixed with parenchyma and surrounded by phloem and 

 pericycle. In the young plant the leaf-trace at first consists of two 

 bundles, one of which eives rise to the vascular System of the bud 

 at the base of the leaf; in the meanwhile what appears to be a 

 vascular commissure (incomplete in the youngest leaves) is formed 

 from the adjoining Strands ot the dictyostele, but it almost immedia- 

 tely divides to form two Strands that enter the leaf as additional 

 trace-bundles. In the petiole these bundles increase by division. The 

 structure of the mature leaf is more complex: a meristele divides 



