132 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



CLASSIFICATION OF PLANTS BY EVOLUTION. 



By Rev. Professor G. Henslow, M.A., F.L.S., V.M.H., &c. 

 [Lecture delivered May 6, 1902.] 



In a previous lecture on " The Making and Unmaking of Flowers " 

 (Journal H.S., vol. xxvi. p. 115) I endeavoured to show how in their 

 evolutionary history flowers had passed from extreme simplicity, as those 

 of a Fir tree, to various degrees of complexity in ordinary flowering 

 plants, often becoming highly "irregular," ajLof the Salvias. 



Then by processes of degradation mlSay flowers become simpler 

 again, until they may be represented by a single stamen, as in Spurges, 

 or by a pistil only. 



In the present lecture I propose showing how these differences re- 

 sulting from evolution provide systematic botanists with the materials 

 for classification. 



The doctrine of evolution maintains that all animals and plants now 

 living have been derived from pre-existing ones ever since the first living 

 beings appeared on this earth. 



How they first came into existence is at present unknown and 

 inconceivable. There is no evidence of any kind whatever of any 

 "spontaneous" generation of living things; and how "protoplasm." or 

 the " physical basis of life," as Huxley called it, can have arisen out of 

 inorganic materials is at present unthinkable. Monists, who so name 

 themselves from their idea of there being "only" matter and force, 

 without any personal mind or other intelligence behind nature, say 

 that if evolution be true, then life must have come out of the mineral 

 kingdom. But science knows nothing of such a " must " in nature. 

 Observation and experiment are the only means of investigation open to 

 scientists. Inductive evidence and experimental verification are their 

 only methods of proof. 



Many evolutionists have looked at the lower forms of Algae as 

 possibly representing at the present day the forerunners of plant life 

 in general ; but we cannot be certain whether existing forms are 

 "primitive" or "degraded;" for even some flowering plants growing in 

 water of a high temperature have acquired a strong resemblance to sea- 

 weeds.* Whichever they are, they have had a world-long ancestral 

 history of which we know nothing. 



I propose, therefore, to pass over all the lower Cryptogams until we 

 reach the highest groups, such as the Fern family. 



We must now consider how evolution works in producing the limit- 

 less numbers of beings on the face of the world. In the first place, it 

 soon becomes obvious that there is not, nor ever has been, any and only a 

 linear series either among animals or plants, but there have been continual 

 branchings oft" from the main stock, and then successive branchings have 

 again risen from those ; so that if all beings were known, past and 



* Podostemacc(C. 



