(vi) 
statement of the idea. Lastly, it has been an object in this book to 
recommend, and to some slight extent at least to illustrate, a larger and 
better conception of species. The writer cannot now attempt to explain 
his meaning by figures; by a comparison of what are called species in 
several of the most accepted manuals of the time; but the evidence 
appears to be sufficient that the term referred to has come to have, often, 
little definite meaning; and that here the investigators of vegetable 
structure who decline to take an interest in systematic botany have in 
fact something to stand on. In this new continent, where so much is to 
be learned, we are less prepared indeed to enter on the long and difficult 
studies which should possibly tend to establish a larger conception of the 
term; and must remain content, for the time, if many of our species, how- 
ever accepted by high authority, are perhaps only members of larger 
species-groups, not yet understood. And, on the other hand (as in Ver- 
rucaria, as we now imperfectly know it) what are called species may in 
part rather be groups which fuller investigation shall one day enable us 
to separate, satisfactorily, into smaller ones. But there can be no ques- 
tion, it is scarcely venturesome to say, with any competent enquirer into 
the prevalent and increasing laxity of conception referred to, that it fore- 
tokens unfavourable results to the future of our studies. 
This is seen, at least, in the very generally assumed value of recent 
experiments on the behaviour of lichen-tissues with certain chemical 
tests; species having thus come at last to have no other meaning than a 
chemical one: namely that they exhibit (so far, it is important to say, as 
the examination has gone) a different reaction from forms with which, in 
every other respect, they are admitted to agree. The writer has since 
found no occasion to qualify the opinions expressed by him already in 
print,' on the systematic value of these experiments. 
Frequent use being made, in the following pages, of some views of 
spore-phenomena published by the author elsewhere, and not now easily 
accessible, place may properly be given to them here. He conceives 
then that while less weight than has often been assumed should be given 
to spore-differences of a merely gradal character, or such others as 
depend only upon dimensions, more than has sometimes been allowed 
should be yielded to those that seem to be typical. Analysis scarcely 
indicates more than two well-defined kinds of lichen-spores, complemented 
} American Naturalist, April, 1268. 
