m Plattt Cytology. 1S5 



detracting from Botany, should be accepted as evidence that 

 the laws gov-erning the life of ever}' plant unit are the more 

 complex and profound, and, therefore, the more worthy of 

 closest study. Coincident with this advance were the studies 

 of Naegeli and Brucke on cell structure and irritability, of 

 Hofmeister on the evolutionary relation of cells and tissues in 

 vascular plants, and of Plerbert on hybridization. 



The third quarter of the centurj- ushers in a galaxy of giant 

 workers, who produced epoch-making works, all founded on 

 cellular morphology and physiology. That this period is 

 marked by the appearance of Darwin's numerous contributions 

 is ample testimony to its fruitfulness. The works of Berkeley, 

 de Bary, Tulasne and Brefeld on the Fungi, of Schwendener 

 on the Lichens, of Hofmeister on the vascular plants, and of 

 Sachs on general physiology were rendered possible only by 

 recognition of the cell as the fundamental unit of plant life. 

 The advances of the quarter century that has now nearly run 

 its course are known to all, but the outstanding feature of the 

 period has been the remarkable increase in the number of 

 workers who are contributing their share to the common 

 stock of morphological and physiological knowledge. No 

 previous quarter of a century in human history has equaled 

 the present in the variety, wealth and novelty of results. 



Let us attempt now to survey our present day knowledge, 

 and inquire regarding lines of progress for the future. A 

 proper conception of plant cytology at once brings before the 

 mind groups of problems, any one of which already claims 

 the attention of specialists from the multiplicit>' of details that 

 bear on it. It may seem presumptuous, therefore, on my part 

 to attempt to review and compare the studies which have 

 already appeared, but every teacher of his science must 

 accomplish this more or less perfectly. Though a somewhat 

 arbitrary' method, I may be permitted, as a matter of con- 

 venience, to glance at cell life from the standpoints of (a) 



