Pomona College Journal op Economic Botany. 



323 



much more slender than those developed in cultures (Plate V. Figure 4). 



The chlaniydospores are produced as swellings of the mycelium, usually 

 intercalary, and there are often several on the same hypha close together 

 like a string of beads. They are circular or ovate cylindrical and appear 

 to have two walls; those which are ovate cylindrical in shape are sometimes 

 divided by transverse walls. They have a slightly uneven surface and are 

 yellowish brown in color. The size of the spherical ones varies from 10 u. 

 -20 u. in diameter, and the oblong ones from 8 u.-lO u. in diameter by 

 20 U.-25 u. in length. They were filled with very large granules of 

 protoplasm. (Plate V. Figure 5.) Strain (E) formed an abundance of 

 them in nutrient agar in thirty days. 



GROWTH ON DIFFERENT MEDIA 



In making a study of the cultural characters the three strains of car- 

 nation Fusarium previously mentioned were used, and in addition two 

 strains of potato Fusarium have been studied in parallel cultures, for the 

 purpose of making comparisons between the carnation and potato strains. 

 One of the potato strains was received from Dr. M. T. Cook of the Dela- 

 ware Experiment Station, and considered by him to be Fusarium oxysporum; 

 morphologically it corresponds to the description of F. oxysporum given by 

 Erwin F. Smith and Deane B. Swingle in Bulletin No. 55 of the Bureau 

 of Plant Industry, but in cultural habits it differs from the descriptions 

 given, for it has a depressed growth on most media and the F. oxysporum 

 described in the bulletin has an aerial growth on most media. The other 

 potato strain was isolated from the stems of diseased potato plants growing 

 in the horticultural garden of the University. All of the cultures of it 

 have originated from a single spore, and in cultural and morphological 

 characters this Fusarium corresponds very closely to F. oxysporum, as 

 described in the bulletin mentioned above. Its parasitism has not, however, 

 been satisfactorily confirmed, either by observation in the field or by inocula- 

 tion experiments. For convenience in describing the cultural characters 

 and the accounts of inoculation experiments with the different strains, sym- 

 bols will be used. The symbols (R), (E), and (IV) refer to carnation 

 strains obtained from Richmond, Elmhurst, and Alameda, respectively; 

 (H) refers to the potato strain received from Delaware, and (VII) to the 

 potato strain isolated from potato plants in the University garden. 



A detailed description of the various culture media used appears in 

 another part of this paper. P. 330. Throe kinds of glass vessels were used : 

 200 c. c. Erlenniieyer fiasks, 70 mm. in diameter through their widest part, 

 test tubes 20 mm. in diameter, and petri dishes 90 mm. in diameter. All 

 transfers were made with a sterile platinum needle and the plantings were 

 made as nearly as possible in the center of each container. Tlic cultures 

 were always made in duplicate and often in series of four or six. In almost 

 every instance growth was apparent to the naked eye in forty-eight hours. 



