INTRODUCTORY 23 



something did not turn up, however, for over three 

 hundred years, when Darwin provided the key to phylo- 

 genetic relationship. In his Philosophia Botanica Linnaeus 

 expressed the view quite definitely that plants could not 

 be classified naturally by any " predetermined mark/' 

 but that it must be left to the future to discover the 

 principles on which any natural taxonomy must be 

 founded. When we come to deal with the work of 

 Linnaeus we shall find that he attempted both methods. 



The earlier classifications were naturally based on 

 morphology only ; the internal structure, or anatomy, 

 was scarcely ever studied, for the simple reason that 

 microscopes had not then been invented. Even when 

 this instrument was added to the botanist's equipment 

 it was long before microtechnique developed sufficiently 

 to permit of the preparation of specimens that might 

 reveal clearly the more minute structure of plant organs. 

 Should you ever have occasion to visit the Royal Botanic 

 Gardens in Edinburgh it will be quite worth your while to 

 inspect the microscope used by Robert Brown in the 

 beginning of the nineteenth century ; I think when you 

 have compared that curiosity with the elaborately 

 finished instruments you are using in the laboratories 

 to-day you will be led to wonder how so much was 

 accomplished with appliances so primitive. Further, the 

 " seeing eye " had to be developed and trained to interpret 

 correctly what the microscope revealed. You yourselves 

 must be conscious that, even with all the mechanical 

 advantages now at your command, the power to express 

 truthfully in a drawing what you see beneath a lens 

 demands for its acquirement long and conscientious 

 application. 



Then again the lower plants formed a constant puzzle 

 to the first botanists ; they did not know what to 

 make of them. These plants had apparently no seeds or 

 other obvious means of reproducing themselves, although 

 that neglected investigator, Cordus, you will remember, 



