236 rnENOLOGicAL observations in 1878. 



By the method of deducing the mean dates of phenologioal pheno- 

 mena previously explained, I propose to compile our jS^aturulists' 

 Calendar for Hertfordshire, a first instalment of which, including 

 the results of observation of insects and birds as well as of plants, 

 is given in the second table accompanying this report (pp. 234, 

 235).* The comparative value of the dates given is shown in this 

 table by an additional column of figures (0 to 3) giving the number 

 of years each species has been observed. This calendar may also 

 be of practical use to our observers as showing when to look out 

 for the occurrences of which a record is desired. For this purpose 

 I have inserted in their most probable position the phenomena 

 of which no record has yet been received, as, if they were omitted 

 altogether from the calendar, they would be likely to be over- 

 looked in future years. I have ventured to substitute the autumn 

 gentian for the field gentian, as we should never get observations 

 of the latter, and may possibly do so of the former, which is of 

 much more frequent occurrence in the county. The two species 

 are very nearly allied and they open their flowers at about the same 

 time. The autumn gentian is the one which has hitherto been most 

 generally observed. It appears in both White's f and Jenyns' :{: 

 Calendars, whilst the field gentian is not given in either, and it 

 is therefore not only the species which is the most likely to be 

 observed in Hertfordshire, but is also the one of which we have 

 published records available for comparison. 



* The following abbreviations are iised in this table : — fl. — flowers open ; 

 ap. — first appears ; sg. — sono- commences, 

 t ' Natural History of Selborne.' 

 X ' Observations in Natural History.' 



