PROF. BOWER: HOOKER LECTURE, I9I7. 107 
HOOKER LECTURE: 
THURSDAY, ?ru JUNE, 1917. 
By Proressor F. O. BOWER, F.R.S., F.L.S. 
Havine for over thirty years occupied the Chair of Botany which Sir William 
Hooker rendered famous by two decades of strenuous work,—in the University 
of Glasgow where Sir Joseph Hooker graduated,—it seems apposite for me to 
take as the subject of the Hooker Memorial Lecture the Natural Classification 
of Plants. For no greater Systematists than the two Hookers existed during 
their own period. And I may be pardoned if I draw my illustrations largely 
from the group of the Filicales, since Sir William Hooker was the greatest 
of descriptive Pteridologists. 
The life-work of the Hookers, father and son, bridged a critical period in 
the progress of Natural Classification, A vital difference of view separated 
their outlook on living organisms. Sir William was the very embodiment 
of the older régime, which laboured under the dogma of fixity of species. 
Sir Joseph was the first botanical exponent of the belief that species are 
mutable. Between them came Charles Darwin, who created that complete 
change of outlook which followed on the publication of the ‘ Origin of 
Species’ in 1859. The effect upon Natural Classification, brought about 
by this revolution of thought, is the theme I shall endeavour to discuss. 
It will not be necessary to refer in detail to the earlier history of Natural 
Classification. We need do no more than take passing note of archaic 
efforts. The recognition and naming of plants must have been initiated 
by primitive man, for plant-names figure in all languages. More specific 
designation and delineation were introduced as a consequence of the appli- 
cation of plants to practical uses as foods, or medicines, or in the arts. The 
mediæval Herbalists depicted many such forms ; but they treated them rather 
as isolated phenomena, illustrating the ability of the Creator, than as having 
any nearer causal relation. Their similarities led to their grouping into 
families ; but the very likeness which the members of these families showed 
was regarded as exhibiting ingenious variation upon a divine plan of con- 
struction. And so, amid admiration tinged with reverence, there grew up 
Systems of Classification, chiefly founded upon external similarity. Such 
early schemes are described as “ artificial,” for they were based upon few 
qualities, and those arbitrarily selected. Convenience was the motor impulse 
LINN. JOURN.—BOTANY, VOL. XLIV, K 
