184 Macfaflaitc — Current Problems 



histological study. In plant physiology Linna;us, Koelreuter 

 and Sprengel had advanced inquiries into the fertilization, 

 pollination and hybridization of plants to a degree that excites 

 our highest admiration. Stephen Hales, Ingen-houss and de 

 Saussure had grappled with problems of plant nutrition. 

 Investigations into plant irritability had been largely confined 

 to naked-eye studies of the leaves of Mimosa, and the stamens 

 of Cynara, Opuutia and Berbcris. The important discovery 

 by Corti in 1772, of protoplasmic circulation in Chara, was 

 lost as a permanent contribution to science for half a century, 

 through a false interpretation of the phenomena. 



The dawn of 1 800 brought, therefore, only moderate hopes 

 for the century now closing. The splendid results achieved, 

 by all the workers who have lived through its years, have 

 been due to unswerving faith in the motto " To the solid 

 ground of nature trusts the mind that builds for aye." 



It would be equally difficult and invidious were I to compare 

 minutely the work and the workers of the century. Rather 

 let me attempt to sketch hastily the great advances which 

 have been made directly or indirectly owing to our increasing 

 knowledge of the cell as the plant unit. In the first quarter 

 of the century numerous investigations were directed to the 

 cell wall as a growing and a mature structure. Each inves- 

 tigator was thereby drawn more and more closely to the 

 formative substance from which such walls proceeded, as 

 furnishing the real basis for explanation of their growth, 

 patterns and uses. In the second quarter of the century, 

 therefore, the researches of Von Mohl, Schleiden and Robert 

 Brown culminated in the recognition of the living cell as the 

 plant unit. Botany thereby attained, for the first time in its 

 history, to the dignity of an exact science. True, the organic 

 units that make up each plant do not usually behave in the 

 manner that chemists and physicists can predict for the 

 simpler molecules with which they deal, but this, instead of 



