XVI PREFACE. 



unobserved, the descriptions have been carefully compared with 

 those of the best British and foreign authors either at the mo- 

 ment of drawing them up or subsequent to their compilation, 

 always with the fresh specimens at hand for renewed compari- 

 sons in the minutest particular. In this way most of the de- 

 scriptions have been gone over twice, and in many instances 

 three times, often at very distant intervals, and with recent spe- 

 cimens from other stations in the island. 



In all cases where the abundance of the species permitted it, 

 the account of each has been compiled from a series of indivi- 

 dual specimens, of diflerent sizes, and, as far as possible, exhi- 

 biting every variety of colour and aspect incident to the plant 

 in its normal state. By thus proceeding we learn to distin- 

 guish what is permanent and essential from that which is but 

 occasional or fortuitous in character, and thus avoid the error 

 which, in minute detail and with scanty means of comparison, 

 we run great risk of committing, — the assumjition of individual 

 peculiarity for absolute and specific difference. 



The use of linear measure has been generally adopted in the 

 descriptive part, since size is often as discriminative of natural 

 objects as form or colour. Every one must have felt how 

 imperfect is the idea conveyed to the mind by the most laboured 

 description of a plant, whilst left in ignorance of its absolute or 

 relative proportions. Besides, the same species of vegetable 

 often varies so much in its dimensions under different condi- 

 tions, favourable or the reverse to its development, that com- 

 parative terms of admeasurement, as high or low, long or short, 

 broad or narrow, large or small, lose all their value and signi- 

 ficancy. 



For all the species described in this Flora, excepting only 

 the very commonest, distinct or special localities are assigned, 

 with a view of saving the too-often hurried stranger, possible 

 loss of time in following up general indications to the object of 

 his search. 



To the majority of stations for the rarer or more local 

 plants will be found added the date of discovery of the species 

 recorded, which to some may have the appearance of giving an 

 undue degree of importance to their detection, without impart- 

 ing information of practical use or interest to the collector. 

 But when it is considered how rapid are the changes which 



