332 SUMMARY OF CURRENT RESEARCHES RELATING TO 



which envelops the seed. From there it spreads through the scale 

 towards the lower surface from which the sporigenic organs emerge. 



J. McMurphy * records an attack of oats in California by an uniden- 

 tified species of Phytophthora. The symptoms of the disease were spots 

 and stripes of varying size along the edges, or a long stripe along the 

 central line of the leaf. The parts attacked are yellow, then whitish, 

 finally they become brown and dry up. 



Rot of Potato Tubers. f—L. A. Hawkins has investigated the effect 

 of Fusarium spp. on potatoes. He found that the crude fibre contents, 

 of the tubers were not reduced, starch and methyl pentosans were not 

 affected appreciably, while the content of other substances was reduced. 

 Fusarium oxysporum and F. radicicola were found to secrete sucrase, 

 maltase, xylanase and diastase. 



Disease of Pecaw Catkins4— The staminate catkins of pecaw. 

 Gary a ilUnmnsis, were discovered by B. B. Higgins to be affected by a 

 parasitic fungus belonging to the genus Microstroma, which resulted in 

 the destruction of most of the anthers, or more especially of the pollen- 

 grains. Apparently no toxic substance was secreted by the fungus, since 

 the protoplasts and nuclei of the infected tissues retained nearly their 

 normal appearance. The changes in the cells indicated starvation. 



The fungus was determined by the writer to be a new variety — var. 

 robustum of 3Iicrostroma JugJandis. Cultures on artificial media were 

 not very successful, only a yeast-like growth being formed. 



Sour Rot of Lemon. § — This is a disease that affects lemons in 

 storage, often causing great loss. The cause has been investigated by 

 Clapton 0. Smith. The trouble was especially evident in California in 

 the summer of 1915, the fruit collected in spring suffering most. 



A microscopic study of the diseased tissues, along with inoculation 

 experiments, proved the cause of the trouble to be the fungus Oospora 

 Citri-aurmitii. It is closely allied to Oospora lactis, but the latter, 

 though so similar morphologically, differs in its non-pathogenic 

 character. When the latter is inoculated on the lemons a slight 

 mycelial growth arises, but the tissues are uninjured. It was found 

 that Oospora Citri-aurantii only attacked fruit through some wound or 

 through spots injured by some other fungus such as Pythiacystis 

 citrophthora, 



Mycorrhiza of the Marattiace86.|| — Frequent references have been 

 made in past years to the presence of a mycorrhizal fungus in the roots 



* Science, xliii. (1916) p. 534. See also Bull. Agric. Intell. Kome, vii. (1916) 

 p. 1212. 



+ Journ. Agric. Eesearch, vi. (1916) pp. 184-96. See also Bot. Gaz.,lxiii.(1917\ 

 p. 88. 



: Phytopathology, vii. (1917) pp. 42-5 (2 figs) and pp. 499-501 (2 figs.). 



§ Phytopathology, vii. (1917) pp. 37-41 (2 figs.). 



II Ann. Bot., xxxi. (1917) pp. 77-99 (1 pi. and figs.). 



