16 THE STIDY Ol' I'LANT.S IN ANCIENT AND MoDEKN TIMES. 



a plant lid, it is true, take one liack as fai- as Aristotle and his school; Imt the ideas 

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

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

 antitjuity than from any intrinsic merit which they possessed. The hi-st experi- 

 mental investigations into the vital phenomena of plants were published by 

 Stephen Hales in ITbS; lait it was not till a hundred years later that this kiml 

 of research really came into vogue. It lirought 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 intjuiry, on 

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

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

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

 and plants. 



Modern science, governed as it is by the desire to laj- liare the causes of all 

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

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

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

 what are the functions of the various bodies which are formed withm 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 

 gi'eat 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 

 whicli are subject to difl^erent external conditions? We are no longer content to 

 determine in what manner the rudimentary organ of a plant is pi'oduced, or hoAv 

 it expands in one case and frequently «livides, 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 by it. 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 coloiu- of the ffowers; 

 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 whicli can only be sought for in a qualitative variation of protoplasm. 

 Specific relationship is explained by attributing it to similaritj^ in the constitution 

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

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



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