of Vegetable Embryology. 227 



that the cavity of the sac elongated itself, under the form of 

 a straight canal, even to the summit of the ovule, and there 

 opened in the endostome and received the extremity of the 

 pollen tube. 



If the truth of these observations be admitted, two very ob- 

 vious conclusions will result. 1st. Our notions regarding the 

 functions of what are called the male and female organs (sta- 

 mens and pistils) must be materially altered, and the sexes of 

 the two sets of organs respectively exchanged ; the anther 

 must be considered as a female ovarium, and each pollen 

 grain as the germ of a new organism, being determined in its 

 development by the secretions of the embryo-sac ; this last 

 structure therefore must be held to correspond with the male 

 organ. 2nd. The process described by Schleiden obviously 

 establishes a close analogy in the development of the embryo 

 between the phanerogamia and those cryptogamia in which 

 the sporules appear to be conversions of the cellular tissue of 

 the foliaceous organs ; for the same part in both furnishes the 

 groundwork of the new plant in each group. 



It has been conceived by Dr. Carpenter* that it is not the 

 extremity of the pollen tube, but one of the pollen granules 

 transmitted along the tube, which is ultimately developed into 

 the embryo, and that hence a still more intimate analogy may 

 be instituted between the reproductive organs of flowering 

 and those of flowerless plants ; a precisely similar function 

 being performed by the theca and the anther, and by the spore 

 and the pollen grain. These doctrines, so deeply affecting 

 some of the most generally received opinions regarding the 

 reproduction of flowering plants, have not passed without the 

 critical investigations of other observers, but have incited 

 MM. Mirbel and Spach to enter on a series of inquiries un- 

 dertaken for the express purpose of testing the accuracy of 

 the statements of Schleiden and Wydler. As far as I am 

 aware, these observations have not yet been published, and 

 are little known in this country ; they were conducted with 

 the view of ascertaining the intimate nature of the develop- 



* Carpenter, Dr. W. B., Principles of General and Comparative Phy- 



R 2 



siology. 



