— 36 — 



There is little largo végétation on the banks of the pond, so 

 that not much shade is provided. Some blackberry and furze 

 bushes were situated on the north-west bank (thèse were eut 

 down in 1911), while a bush of Salix caprea (from 3-4 feet 

 high) grows in the water, a little way from the north-west 

 bank. On the other hand abunclant aquatic and marsh végéta- 

 tion develops in the pond during the mild period of the ycar 

 and must then contribute very largely to the shading of the 

 algal végétation and may possibly enter into compétition with 

 it Thèse forins furnish a substratum for a rich epiphytic flora. 



Rainfall ai Harpenden-Rothamsted (in inches) (1) . 



The most important meteorological data for our purposes are 

 those concerning rainfall, sunshine and température Withrefe- 

 rénee to the rainfall, attention may be drawn to the fact that 



(!) Cf. Hopkinson, IQ08, pp. 40, 41, 230, 231: Hopkinson, 1912, pp.-88, 89, 

 120, 121, 168, 169, 262, 263. 



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