464 ORGANOLOGr. 



must then act upon the pericarp, and thus determine the position of the 

 embryo. In short, without consideration, an imprudent word has been 

 thrust forward, and supposed to afford an explanation. I have already 

 observed that no botanist is justified in saying absolutely and without 

 reason how much or how little he will adopt of other systems for his own 

 use, or as a point to start from. When he avails himself of other sciences, 

 he must clearly comprehend the notions of these sciences, or he will but 

 make himself ridiculous. But when, in the nineteenth century, a pro- 

 fessor of physics can so err in fundamental principles as to say " action 

 from contact is improbable, because we know no example in which a 

 body at rest can set another body in motion," more at present can 

 scarcely be demanded of botanists. 



It would be too much to assert the impossibility of gravitation being 

 the cause of the phenomena above mentioned ; but we have nothing 

 to do with the power of gravitation, because we have no object on which 

 it could act. 



The various fancies respecting the peculiar vessels which are em- 

 ployed in conveying the nutritive matter from the seed-leaves to the 

 radicle, and all similar theories which are found in old works, I ha\ 7 e 

 left without notice, for they are altogether worthless. I will, however, 

 enumerate some of the matters demanding examination, which will afford 

 a more intimate knowledge of the processes of germination. 



I. An explanation of the cause why, in the embryo and the albumen, 

 the starch is dissolved and the oil of fat is decomposed. 



II. An accurate determination of the degree of heat present during 

 germination, and a comparison of the same with the quantities of carbon 

 and hydrogen which are consumed. 



III. An exact quantitative analysis of germinating plants, and of their 

 separate parts in all stages of germination ; with an exact quantitative 

 determination of the proportion of water taken up, and of gases inter- 

 changed, as well in embryos containing starch as in those containing 

 oil. It is evident that such analyses must be constantly pursued with the 

 help of the microscope. 



IV. A repetition of the experiments made by Knight, with a view to 

 ascertain whether the germination arid continued growth might not be 

 made in a direction the reverse of that which is usual, if earth should be 

 placed upon them from above, whilst they should be subjected to strong 

 light from below. 



The development of the spores of Cryptogamia, which is also termed 

 germination, finds no analogy here but with the development of the 

 pollen-grains in the embryo. In each of these, however, the physical 

 and chemical conditions are different, and a special investigation of the 

 process of development, with respect to the chemical and physical con- 

 ditions of germinating ferns, is much to be desired ; but there are 

 many preliminary difficulties to be overcome. A close investigation of 

 the kind pointed out in the third section above would tend to the ex- 

 planation of many of the laws of vegetation, if it could be followed out 

 with a number of the Algce, for instance, Spirogyra, and in this case the 

 natural position of the plant would greatly facilitate the investigation. 



C. Of Growth. 



187. Growth of plants generally is the increase in their volume 

 and their mass. In the scientific treatment of the subject, we 



