914 



SCIENCE 



[N. S. Vol. XXIX. No. 753 



vary from the conditions in adjacent localities 

 where the trees remain healthy. 

 The Present Treatment of Monotypic Genera of 

 Fungi: C. L. Shear, U. S. Department of Agri- 

 culture, Washington, D. C. 



The following seven monotypic genera of fungi, 

 Ocelosphcsria Sacc, Cryptosphwria Grev., Cylin- 

 drosporium Grev., Isothea Ft., Ntemaspora Willd., 

 Septaria Fr., Sphceropsis Lev., selected at random 

 from the Pyrenomycetes and Fungi Imperfect! are 

 cited as examples of the present condition of the 

 nomenclature of the fungi as represented in recent 

 general systematic works such as Saccardo, " Syl- 

 loge Fungorum," Engler and Prantl, " Pflanzen- 

 familien," Rabenhorst's " Cryptogamenflora " and 

 Ellis and Everhart's " North American Pyreno- 

 mycetes." The rule adopted by the international 

 zoologists and the American botanists that a 

 monotypic genus must always contain its mono- 

 type appears to receive no particular recognition. 

 The original monotypes of the genera mentioned 

 have been transferred to other genera of later 

 date and the original generic names are now 

 applied to other groups of species and frequently 

 attributed to other authors. The desirability of 

 recognizing the fixity of monotypic genera and 

 genera having a species specifically designated as 

 type is suggested as an essential part of the rules 

 to be formulated by the section of the Interna- 

 tional Botanical Congress which is to consider 

 the nomenclature of cellular cryptogams at its 

 meeting at Brussels in 1910. 



A Bacterial Disease of the Peach: James Birch 

 RoBEB, U. S. Department of Agriculture, Wash- 

 ington, D. C. 



For the past three seasons the writer has made 

 observations on a disease of peach leaves, twigs 

 and fruit, evidently caused by a bacterium. 



The form on the leaves is the commonest and 

 most widespread. It causes somewhat angular 

 purplish-brown spots one eighth to one fourth 

 inch in diameter, which soon drop out, giving a 

 shot-hole eflfect. Serious outbreaks of the disease 

 cause a premature defoliation of the trees. This 

 leaf spot was first seen by the writer on peach 

 leaves collected in Georgia in 1903 by Mr. P. J. 

 O'Gara, of the Department of Agriculture. Dur- 

 ing the same season Clinton observed a disease, 

 evidently the same, in Connecticut and reported 

 in the Report of the Connecticut Agricultural 

 Experiment Station for 1903, Part IV., page 337. 

 In 1906, 1907 and 1908 the writer found the 

 disease to be prevalent throughout the south and 

 middle west. 



In August, 1906, pure cultures of an organism 

 were obtained from the leaf spots and in the fol- 

 lowing spring inoculations made with this organ- 

 ism caused spots in all respects similar to those 

 from which the bacterium was originally obtained. 

 The same organism was again obtained in pure 

 cultures from the spots which were artificially 

 produced. 



The disease on the twigs was first observed in 

 1907 at Siloam Springs, Ark. It kills the bark 

 of young shoots, forming purplish-black, slightly 

 sunken areas one eighth to one fourth inch wide, 

 which may extend for two or three inches along 

 the stem. In 1908 this twig disease was found in 

 an orchard in Bentonville, Ark. Numerous sec- 

 tions through the youngest spots showed the 

 presence of bacteria in large quantities and by the 

 poured plate method cultures of an organism 

 similar to that from which the leaf spots were 

 obtained. No attempt has been made as yet to 

 produce this form of the disease by inoculation. 



The disease on the fruit is very characteristic. 

 It was found in two orchards at Bentonville, Ark., 

 during the past season. It causes a very small 

 purplish spot over which the skin soon cracks, 

 in either a straight or an angular way. The spots 

 are usually very numerous (two hundred and fifty 

 have been counted on one side of a peach), and 

 often coalesce so that the cracks become continu- 

 ous and extend for an inch or more. Sections 

 through the smallest spots showed that bacteria 

 were present in abundance and evidently the cause 

 of the trouble. 



Though not entirely proved, it is assumed that 

 the three forms of the disease mentioned above are 

 caused by Bacterium pruni Erw. Smith, which 

 causes the bacterial black spot of the plum, for 

 the following reasons: (I) the leaf spot of plums 

 caused by B, pruni is very similar in appearance 

 to that of the peach; (2) by inoculation with 

 pure cultures of B. pruni, spots may be produced 

 on peach leaves similar in all respects to those 

 occurring naturally; (3) the organism isolated 

 from the peach leaf spot and twig spot have the 

 same cultural characteristics in all the difi'erent 

 media in which they have been grown as B. pruni; 

 (4) though the organism has not been obtained 

 in pure cultures from the peach fruit spots, the 

 megascopic and microscopic appearance of these 

 spots is identical with the small spots on the 

 plums, especially those which result from late 

 infections. 



The Cause of Trembles and Milk Sickness: E. L. 

 MosELEY, Sandusky High School, Sandusky, 0. 



