xc INTEODUCTION 



by means of a key-list of letters and tlieir eqiiivalents at the begin- 

 ning of the catalogue. A separate catalogue was used for each 

 division. So far as possible, specimens were dried of all plants that 

 could not be named in the field ; but on account of the number of 

 plants collected, and the amount of ground covered, it was soon 

 found impossible to collect Faihi and other bulky specimens. The 

 "billows suffered from the same cause, and on account of the 

 impossibihty of revisiting places at different times of year. My 

 hasty surveys were likewise insufficient for the working out of the 

 distribution of critical forms : our knowledge of such plants can 

 only be acquired by slow and patient observation. In certain 

 groups, however, notably Characece, large collections were made, 

 which have much extended our knowledge of their range in the 

 country. 



In the case of each division, it was found advantageous, when 

 about three days' work had been carried out, to form, from the 

 marked catalogue, a desiderata-list of all common plants not yet 

 seen, and to keep this list prominently in view ; otherwise there was 

 a danger that even conspicuous plants of universal occurrence might 

 escape being noted. The number of days devoted to each division 

 was, as has been already stated, determined by the amount of work 

 done in each by previous observers, and the first four years' work 

 was carried out according to this estimate. At the end of the fourth 

 year, a table of distribution was constructed for the whole flora in 

 the forty divisions, including both my own and previous work. 

 From this table desiderata-lists were formed for each division, of all 

 yet unrecorded plants likely to occm- in each, and the last season's 

 work was distributed among the divisions in proportion to the lenc^-th 

 of these lists. 



In estimating the time devoted to each division, six hours or 

 more in the field was reckoned as a " day" ; less than six hours as a 

 half-day. The ordinary " day," however, consisted of twelve hours 

 — 8.30 a.m. to 8.30 p.m. — and the walking distance covered per day 

 averaged 20 to 2? miles, with a minimum of about 15, and a 

 maximum of 35. Anything over a 25-mile day, however, generally 

 meant a steady tramp as the beginning or end of the day's work. 



The rate of growth of the county lists is a rather interesting 



