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for studying the subject from a practical point of view. 

 The more technical difficulties may be due to want of 

 training in botanical subjects, or may arise because suit- 

 able literature is not available. For such as these latter, 

 no amount of mere thinking can be of much use. One 

 must fall back on others more fortunate in their wide 

 reading and experience. 



Two of my difficulties may not be difficulties to others — 

 indeed they may not trouble them at all. The first was 

 brought back to my mind by certain remarks of Dr. 

 Stansfield's in a recent article on " Lastrea dilatata and 

 its Allies. " In one place he mentions two ferns which 

 are " regarded by Wollaston as distinct species, by others 

 as varieties only.'' In another place, he remarks of a 

 certain fern, " I do not therefore regard it as a species, nor 

 even as a good form." 



This latter suggests that Dr. Stansfield has in his mind 

 a clear idea as to what constitutes a " distinct species." 

 The question that occurred to me was — what are the 

 characters which lead the botanist to decide whether a 

 particular plant is a distinct species, or variety, or form, 

 of a particular genus ? 



In asking this question, I may say that I realise to a 

 considerable extent the difficulties that would arise if 

 anyone attempted to answer it. I realise that any written- 

 description would be ineffectual in the absence of wide 

 experience and botanical instinct. I fear I am rushing in 

 where wise men tread gently. A large number of the 

 points one has already learnt for oneself, and one might 

 be inclined to argue that if expert botanists cannot agree 

 on the subject, it is not worth the while of a mere amateur 

 to worry about it. But this, surely, is an unprogressive 

 attitude, and problems would never be solved if a sufficient 

 number of people did not worry about them. 



The trouble is, perhaps, that the greater one's experi- 



