APPENDIX VI 



THE LYCHEE (LITCHI CHINENSIS) A MYCORHIZAL PLANT. 



By FREDERICK V. COVILLE 



Botanist, United States Department of Agriculture 



The lychee plants brought to America by the United States 

 Department of Agriculture and held in the greenhouse for pur- 

 poses of study and propagation have seldom grown with luxuriance. 

 Their stunted appearance and the poverty of their root develop- 

 ment under the ordinary treatment of greenhouse plants indicated 

 a lack of nutrition, and the idea suggested itself that the lychee 

 might belong to that class of plants which require, or thrive best 

 in, an acid soil. 



For a preliminary experiment, twelve seedling lychee plants 

 were procured from the Office of Foreign Seed and Plant Intro- 

 duction (No. 46568). Three different soil mixtures were used, four 

 plants being potted in each. For our present purpose only two of 

 these soils need to be considered. One of these is the potting soil 

 used for ordinary greenhouse purposes, made up of one part of 

 rich loam, by bulk, one part of sand, and one part of well-rotted 

 cow-manure. The other soil consists of two parts of upland peat 

 and one part of clean sand. 



The plants were potted in these two soils June 21, 1920, 



in 4-inch pots. The pots were plunged in sand, in a greenhouse in 



which the minimum temperature in winter is 55 Fahr. at night, 



'70 in the daytime. In spring, summer, and fall the temperature 



goes much higher. 



The difference in behavior of the lychee in the two soils 

 is conspicuous, as is shown by typical plants from the two lots, 

 seven months after potting, reproduced in Plate XX. The 

 growth of the plants in the ordinary potting soil is very feeble; in 

 the acid soil it is free and luxuriant. 



Corresponding inequalities of growth have taken place 

 underground. In the ordinary soil the root development is feeble 

 and is confined chiefly to stout, unbranched leaders which have 

 pushed through to the bottom of the pot. In the acid soil the 

 plants have produced similar root leaders, but more freely, and in 

 addition there is an extensive development of smaller much- 

 branched roots. These lie chiefly at the sides of the root-ball, 

 against the wall of the pot. Some of the plants in the ordinary soil 

 have developed similar branched roots, but much less extensively. 



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