— 39 — 



years (ignoring 1910) do not differ very ap'preciably from one 

 another in this respect. Attention may also be drawn to tbe 

 large amount of sunshine in Mardi 1907, in April 1900 

 and 1909, in May 1909, in July-September 1906; to tho small 

 ûumber of hours of sunshine in Mardi 1909, June 1909. Sep- 

 temberl90o and 1909, November 1906, December 1905 and 1908. 

 In considering the températures we hâve adopted those taken 

 at S 1 Albans, for which we are indebted to Mr. Hopkinson's 

 publications; S' Albans is suffiçiently near to the pond to make 

 itunlikely that there would hâve been any marked différence in 

 température. Apart from thèse temperature-data, Mr. Salisbury 

 also furnislied us with the températures of air and water at the 

 time of collection (1) , as well as with the average minimum and 

 maximum températures during the period intervening between 

 the collection of two successive samples. We hâve not consid- 

 ered it necessary to give thèse data in extenso, but occasional 

 référence will be made to tliem in what iollows. In the case of 

 Abbot's pool thèse data {cf. Fritsch and Rich, 1909, pp. 30, 31) 

 showed that during the win'er the température of the water 

 was generally iower than that of the air, wliile in the snmmer 

 it was often the otlier way round. In Barton's pond no s.ueh 

 marked relation between the températures of air and water is 

 apparent; at one time the air was warmer than the water, at 

 another the water warmer than the air, and this occurred quite 

 indiscriminately, both in winter and su m mer. In fact there 

 can be no doubt that in Barton's pond the température of the 

 water is subject to much more fréquent and marked oscillations 

 than in Abbot's pool, and this is no doubt due to the very 

 varying amount of water in the former pond. 



B. — The fora of Barton's pond. 



The pond exhibits a fairly well-developed Phanérogamic 

 flora { --\ which shows marked periodicity. Lemna minor is 

 the most regular constituent of the Phanérogamic flora; it is 

 generally scanty in amount during the winter-months, but with 

 the ad vent of spring it tends to cover a large part of the surface. 



| 1 i We do not think that thèse particular data are of any considérable value 

 although we formerly advocated the taking of them. 



(i 1 ) Mr. Salisbury has kindly tùrnisheil us with thèse détails regarding the 

 Phanérogamic tlora. 



