ADDRESS. lix 



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

 us familiar with particulars relating to the structure and functions of the 

 vegetable creation, which the ruder methods of investigation before resorted 

 to would never have revealed to us. 



We owe to them the interesting discoveries of Brown and Adolphe Brong- 

 niart, 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 investing membranes. Thus much at least appears 

 to be fully ascertained ; but in alluding to the observations of others who 

 have endeavoured to push their scrutiny still further, it becomes me to speak 

 with more diffidence, inasmuch as the office which the pollen discharges in 

 the act of fecundation is still a matter of dispute, between such men as 

 Schleiden and Schacht on the one side, and Hofmeister, Moll, &c. on the other. 



Whilst, however, this controversy 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 all 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 in respect to their organs of 

 reproduction ; not, indeed, as Hedwig supposed, that parts corresponding to 

 stamens and pistils in appearance and structure can be discovered 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, ap- 

 pears to exercise in one case the function of the male, in another of the female, 

 as is found the case in certain of the Confervse, we arrive at length at the com- 

 plicated machinery exhibited in flowering plants, in which the cell containing 

 the fecundating principle is first matured in the stamen, and afterwards trans- 

 mitted through an elaborate apparatus to the cells of the ovule, which is in 

 like manner enveloped in its matrix, and protected by the series of investing 

 membranes which constitutes the seed-veissel. Thus, as Goethe long ago 

 observed, and as modern Physiologists have since shown to be the case, the 

 more imperfect a being is, the more its individual parts resemble each other 

 — the progress of development, both in the animal and vegetable kingdom, 

 always proceeding from the like to the unlike, from the general to the 

 particular. 



But whilst the researches of Brown and others have proved, that there is no 

 abrupt line of division in the vegetable kingdom, and that one common struc- 

 ture pervades the whole ; the later inquiries of Suminski, Hofmeister, Unger, 

 Griffith, and Henfrey, have pointed out several curious and unlooked-for 

 analogies between plants and animals. 



I may mention, in the first place, as an instance of this analogy, the ex- 

 istence of moving molecules or phytosperms in the antheridia of Ferns and 

 other Cryptogams, borne out, as it has been in so remarkable a manner, by 

 the almost simultaneous observations of BischofF and Meissner on the egg, 

 confirmatory of those formerly announced by Barry and Newport; and by 

 the researches of Suminski, Thuret, and Pringsheim, With respect to the 

 ovule of plants. I may refer you also to a paper read at the last Meeting of 

 the Association, by Dr. Cohn of Breslau, who, in bringing tliis subject before 

 the Natural History Section, adduced instances of a distinction of sexes which 

 had come under his observation in the lower Algse. 



