ITS CONCLUSIONS PLASTIC 13 
others and vary the general result. It will be seen in the discussions 
which follow how largely this is so in the morphology of plants. 
It may be objected that conclusions which are so plastic are little 
better than expressions of personal taste, or even of temperament: that 
the study of Comparative Morphology is therefore calculated to dishearten 
its votaries, while the non-specialist public, which is compelled to take 
its information at second hand, will be bewildered, and will conclude 
that it is useless to pursue a science which shows so little stability. But 
even where problems are apparently insoluble under circumstances of 
present knowledge, it is a satisfaction to most minds to entertain an 
opinion, even if that opinion be of a theoretical nature, and be liable to 
future modification or ultimate disproof. On-the other hand, as regards 
‘the actual progress of morphology, those who follow its history with 
sympathetic care will gain heart when they compare the present position 
with that of a generation ago. And especially for Botanists it is encouraging 
to think that it is little more than half a century since the history of the 
life-cycle of a Fern was first completed by Suminsky. In some sixty years 
a vast array of kindred facts has been acquired, and a theoretic super- 
structure is being raised upon them which, though still protean, is gradually 
acquiring some settled form. Never in its history has the advance of 
morphological thought been so rapid as at present. But in no field of 
morphological research has investigation been more amply rewarded than 
in palaeophytology: the luminous facts derived from fossils are shedding 
a fresh and a direct light upon obscure. problems, such as the origin of 
the seed-habit, and helping us to locate such difficult groups as the 
Psilotaceae and Equisetineae. When we regard these rapid advances. and 
truly estimate the influence they bring to bear in strengthening the positions 
already indicated by morphological theory, we shall not only see that this 
branch of the science is very actively alive, but also that its theorisings 
are not merely unsubstantial figments of the mind. 
Considerations such as these go far to justify the statement in the 
present work of a theoretical view of the origin of a Land-Flora. Some 
may deem the opinions expressed as unduly speculative, but in the first 
place, they are based upon a wide area of fact, and secondly, as above 
remarked, comparative morphology must necessarily assume a_ theoretical 
form under present conditions. We have seen that its conclusions as to 
descent are at best the result of a balancing of probabilities. As long as 
this is clearly understood by the reader; and the author abstains from any 
dogmatic attitude, good should come from any duly reasoned statement, 
even though, like the present, it may be of a theoretical nature. A working 
hypothesis, open like others to refutation, is better than no hypothesis 
at all. This is the position consciously adopted here, for it is believed 
that the full statement of even a speculative view will stimulate enquiry, 
which may lead towards its ultimate proof or disproof. 
