MECHANICS AND USEFUL ARTS. 27 



direct the practical labors of the agriculturist ? I need not go further than 

 the works of Baron Liebig for an answer to this question. I may appeal, for 

 instance, to the extensive employment of guano at the present time, first intro- 

 duced in consequence of his suggestions ; I may refer to the substitution of 

 mineral phosphates for bones, founded upon his explanation of the sources 

 from which the latter substance derives its efficacy as a manure ; and I may 

 allude more especially to his refutation of the humus theory, to which even 

 the great Saussure gave his adhesion, and the reception of which was calcu- 

 lated to vitiate, not a few processes only, but the entire system of our husban- 

 dry. 

 But it is time to hasten on to certain other departments of Natural Science- 



DISCOVERIES IX BOTANICAL SCIENCE. 



In Botany and Vegetable Physiology it cannot perhaps be said, that whole 

 provinces have been added to the domain of the science within twenty years, 

 as we have seen to be the case in our review of the progress of chemistry. 

 The improvements in the microscope which have since taken place render us 

 familiar with particulars relating to the structure and functions of the vege- 

 table creation, which the ruder methods of investigation before resorted to 

 would never have revealed to us. We owe to them the interesting dis- 

 coveries of Brown and Adolphe Brongniart, as to the mode in which the 

 pollen is brought into immediate contact with the ovules, by means of the 

 tubes which it protrudes by a prolongation of the innermost of its two invest- 

 ing membranes. Thus much, at least, appears to be fully ascertained ; but, 

 in alluding to the observations of others, who have endeavored to push their 

 scrutiny still further, it becomes me to speak with more diffidence, inasmuch 

 as the office which the pollen discharges hi the act of fecundation is still a 

 matter of dispute between such men as Schleiden and Schacht on the one 

 side, and Hofineister, Moll, &c., on the other. Whilst, however, this contro- 

 versy continues, it is something at least to know that the vivifying principle, 

 whatever it may be, is actually transmitted to the part where its influence is 

 to be exerted, and not kept apart from it, as we were formerly compelled to 

 assume, by that long intervening plexus of fibres, or tubes, which constitutes 

 the style. To the microscope also we owe ah 1 that is as yet known with 

 respect to the reproductive process in cryptogamous plants, which are now 

 shown to possess a structure analogous to that of flowering ones hi respect to 

 their organs of reproduction ; not, indeed, as Hedwig supposed, that parts 

 corresponding to stamens and pistils in appearance and structure can be dis- 

 covered in them, but that as the primary distinction of sexes seems to run 

 throughout the Vegetable Kingdom, new parts are superadded to a structure 

 common to all as we ascend in the scale of creation, until from the simple 

 cell, which, in consequence of some differences of structure, to our eyes 

 inappreciable, appears to exercise in one case the function of the male, in an- 

 other of the female, as is found the case in certain of the Confervas, we 

 arrive at length at the complicated machinery exhibited in flowering plants, 

 in which the cell containing the fecundating principle is first matured in the 

 stamen, and afterwards transmitted, through an elaborate apparatus, to the 



