CORRESPONDENCE WITH HIS FAMILY. 125 



Mrs. Stebbing and I go down to S. together on Friday in a 

 p. chaise. I shall not forget to take my sister's present. 



Yours affect., 



GIL. WHITE. 



The water-snails, two or three species now begin to be 



buoyant, and to crawl with their bellies upwards on or 



against the surface of the water. We have none round 

 Seleburne *. 



LETTER XXII. 



TO SAMUEL BARKER. 



Selborne, July 1, 1776. 



Dear Sam, 

 In the larger plants in general I found no difficulty at all, 

 being assisted by Linn., Hudson, Ray's Synopsis Stirpium, 

 &c. : but as to the mosses, I did not care to meddle, because 

 they were become too minute for my eyes, before they begun 

 to be employed in those enquiries. As to the genera of Orchis, 

 Ophrys, and Serapias, there is great obscurity among them, 

 as Linn, tacitly acknowledges, by calling in the distinction of 

 their roots in his specific descriptions. In his system the 

 distinctions should lie in the corolla, stalks, leaves. As to the 

 different sorts of garden fruits, they are the production of 

 cultivation, and belong only incidentally to the Linn, system, 

 but are to be sought for in Miller's Diet. &c. As to the 



flowers, when the pollen is ripe, become suddenly detached from the 

 plant, rise at once to the surface, burst open, and scatter the pollen over 

 the female flowers already open to receive it. — T. B.] 



* [The buoyancy of the Limnreidse, floating with the body and shell 

 hanging down below the surface of the water, is caused not only by the 

 air within the pulmonary cavity, but also by a certain degree of hollow- 

 ing of the surface of the foot, the margin of which, by a sort of undulatory 

 motion, conducts the animal slowly along the surface of the water. — T. B.] 



