16 THE STUDY OF PLANTS IN ANCIENT AND MODERN TIMES. 



a plant do, it is true, take one back as far as Aristotle and his school; but the ideas 

 of vegetable life entertained at that time are scarcely more than fantastic dreams; 

 and the recognition now accorded to them springs rather from a reverence for 

 antiquity than from any intrinsic merit which they possessed. The first experi- 

 mental investigations into the vital phenomena of plants were published by 

 Stephen Hales in 1718; but it was not till a hundred years later that this kind 

 of research really came into vogue. It brought with it the conception of a cell 

 as a miniature chemical laboratory, and looked for mechanical interpretations of 

 the phenomena of nutrition, sap-circulation, growth, movement — in short, all vital 

 processes — and for some connection between these processes and the external form. 

 Whereas, in the case of descriptive and speculative botany, and in the study of 

 development, the entire plant was first taken into consideration, next its several 

 parts, and lastly the cells and protoplasm; in the new department of inquiry, on 

 the contrary, the complete histories of the ultimate organs were studied first 

 of all, then the significance of the diflferent forms of the several members, and lastly 

 the phenomena occasioned by the aggregate life of all the various kinds of animals 

 and plants. 



Modem science, governed as it is by the desire to lay bare the causes of all 

 phenomena, is no longer satisfied with knowledge concerning the existence of cells, 

 the arrangement of the difierent forms of cell, the development of their contents, 

 and the changes undergone by cell-membranes. At the present day we inquire 

 what are the functions of the various bodies which are formed within the proto- 

 plasm? Why is the cell-membrane thickened at a particular spot in a particular 

 manner? What is the meaning of all the tubes and passages which exhibit such 

 great diversity of size and shape? What part is played by the peculiar mouths of 

 these channels, and why do they vary so greatly in shape and distribution in plants 

 which are subject to different external conditions? We are no longer content to 

 determine in what manner the rudimentary organ of a plant is produced, or how 

 it expands in one case and frequently divides, or else is arrested in its growth and 

 shrivels up; but we inquire the reason why one rudiment grows and develops 

 whilst another is obliterated. For us no fact is without significance. Our 

 curiosity extends to the shape, size, and direction of the roots; to the configuration, 

 venation, and insertion of the leaves; to the structure and colour of the flowers; 

 and to the form of the fruit and seeds; and we assume that even each thorn, 

 prickle, or hair has a definite function to fulfil. But efforts are also made to 

 explain the mutual relations of the different organs of a plant, and the relations 

 between different species of plants which grow together. Lastly, this department 

 of research (the rapid growth of which is due to Darwin) includes amongst its 

 objects a solution of the problem of the ultimate grounds of morphological variety, 

 the causes of which can only be sought for in a qualitative variation of protoplasm. 

 Specific relationship is explained by attributing it to similarity in the constitution 

 of the protoplasm of allied species, and the affinities exhibited by living and extinct 

 plants are used as means of unfolding the hereditary connection between the 



