34 SOME AMERICAN MEDICAL BOTANISTS 



appeared his Nova Plantarum Genera, dedicated 

 to Peter Collinson, 1 both of which papers were 

 printed at Nuremberg, 1769. Collinson was very 

 keen on making exchanges of natural history 

 specimens with Americans, and strongly urged 

 them to cultivate silk, flax, hemp and wine. Mit- 

 chell must have enjoyed having such an interested 

 friend in the old country, and would anxiously 

 await from him the opinion expressed by the 

 Royal Society concerning a paper on The Causes 

 of the Different Colours of People in Different 

 Climates (1743), which Collinson was to read 

 for him, in 1744. The paper finally appeared in 

 the Society's Philosophical Transactions (vol. 

 xliii). 



However, in 1746, Mitchell was himself in 

 London. He had had a bad journey, for the ship 

 was captured by Spanish pirates, and Linnaeus, 

 writing to Haller (1746), says: 2 



" All the plants sent me from New York have 

 fallen into the hands of the Spaniards, along with 

 those that Dr. Mitchell has for many years been 

 collecting in Virginia. He himself is returned 

 safe, though in a desperate condition, to England. 



" I have lost, in the same ship, numerous speci- 

 mens and descriptions sent by Governor Golden 

 from New York." 



1 Peter Collinson, naturalist and antiquary, 1694-1763. 



2 Correspondence of Linnaeus, vol. ii. 



