ADDRESS. 11 



delivered to the Geographical Society in 1878, Thiselton Dyer himself 

 has sammed up the present state of the subject, and contributed an 

 important addition to our knowledge of plant- distribution by showing 

 how its main features may be explained by migration in latitude from 

 north to south without recourse being had to a submerged southern conti- 

 nent for explaining the features common to South Africa, Australia, and 

 America. 



The fact that systematic and geographical botany have claimed a 

 preponderating share of the attention of British phytologists, is no doubt 

 in great measure due to the ever- expanding area of the British Empire, 

 and the rich botanical treasures which we are continually receiving from 

 India and our numerous colonies. The series of Indian and Colonial Floras, 

 published under the direction of the authorities at Kew, and the ' Genera 

 Plantarum ' of Bentham and Hooker, are certainly an honor to our 

 country. To similar causes we may trace the rise and rapid progress of 

 economic botany, to which the late Sir W. Hooker so greatly contributed. 



In vegetable physiology some of the most striking researches have 

 been on the effect produced by rays of light of different refrangibility. 

 Daubeny, Draper, and Sachs have shown that the light of the red end 

 of the spectrum is more effective than that of the blue, so far as the decom- 

 position of carbon dioxide (carbonic acid) is concerned. 



Nothing could have appeared less likely than that researches into the 

 theory of spontaneous generation should have led to practical improve- 

 ments in medical science. Yet such has been the case. Only a few 

 years ago Bacteria seemed mere scientific curiosities. It had long been 

 known that an infusion — say, of hay — would, if exposed to the atmo- 

 sphere, be found, after a certain time, to teem with living forms. Even 

 those few who still believe that life would be spontaneously generated 

 in such an infusion, will admit that these minute organisms are, if not 

 entirely, yet mainly, derived from germs floating in our atmosphere ; and 

 if precautions are taken to exclude such germs, as in the careful experi- 

 ments especially of Pasteur, Tyndall, and Robei'ts, everyone will grant 

 that in ninety-nine cases out of a hundred no such development of life 

 will take place. In 1836-7 Cagniard de la Tour and Schwann indepen- 

 dently showed that fermentation was no mere chemical process, but was 

 due to the presence of a microscopic plant. But, more than this, it has 

 been gradually established that putrefaction is also the work of micro- 

 scopic organisms. Thirty years, however, elapsed before these important 

 discoveries received any practical application. 



At length, however, they have led to most important results in Surgery. 

 One reason why compound fractures are so dangerous is because, the skin 

 being broken, the air obtains access to the wound, bringing with it 

 innumerable germs, which too often set up putrefying action. Lister 

 first made a practical application of these observations. He set himself 

 to find some substance capable of killing the germs without being itself 

 too potent a caustic, and he found that dilute carbolic acid fulfilled these 



