152 THE LYCHEE AND LUNGAN 



The characteristic of greatest interest, however, in the acid- 

 soil plants is that their branched roots are covered with tubercles, 

 and that these tubercles are gorged with mycorhizal fungi. The 

 appearance and the abundance of these tubercles are well shown in 

 Plate XXI. 



Dr. Emil G. Arzberger, of the Office of Crop Technology, 

 with exquisite technique, has fixed, stained, and sectioned the 

 tubercles, and has made drawings and photographs. His descrip- 

 tions and illustrations leave no question that these tubercles are 

 genuine symbiotic mycorhizas. Three photographs and four 

 drawings by Dr. Arzberger, showing the mycorhizal fungi in the 

 cells of the tubercles, at enlargements of 195 to 830 diameters, are 

 reproduced in Plates XXII and XXIII. None of the plants in 

 the ordinary soil developed these tubercles. 



This experiment was conducted without knowledge that 

 Professor Groff was writing a book on the lychee. Ordinarily such 

 an experiment would be repeated many times for verification before 

 the results were published, but it has seemed desirable to publish 

 this brief statement at once, since the experiment points to con- 

 clusions of fundamental significance in the life history of the 

 lychee and suggests a definite and unusual line of agricultural 

 practice, at the very beginning of the culture of the lychee in the 

 United States. 



The experiment indicates that the mycorhizal fungus is 

 beneficial to the lychee plant, probably, indeed, essential to its 

 vigorous growth and productivity; that an acid soil is necessary 

 for the maintenance of. the fungus; and that a soil of peaty type 

 is the most promising for lychee culture. Repeated experiments 

 should be made to test the validity of these indications. Dr. 

 Arzberger is making a detailed study of the lychee root fungus for 

 more extended publication. 



Although these mycorhizal tubercles presumably occur on 

 the roots of the lychee in China, they have never been recorded or 

 observed there, so far as Professor Groff is aware. A reexamination 

 of lychee culture in China, in the light of the present experiment, 

 will be of great interest, for it is likely to be found that this industry 

 is a genuine acid-soil culture, developed as such by the Chinese, 

 unconsciously and empirically, from the ancient and cumulative 

 experience of that amazing people. 



