574 ON THE PLURALITY AND DEVELOPMENT 



regard to Cycas, might be considered the revival of the 

 general hypothesis advanced by Morland in 1703/ and some 

 years afterwards adopted, but without acknowledgment, 

 by C. J. Geoffrey,^ and which seems to have entirely origi- 

 nated in the discovery by Grew of the existence of a for- 

 amen opposite to the radicle of the embryo in the ripe 

 seeds of some Leguminous plants.* 



But as M. du Petit Thouars had evidently no intention 

 of extending his hypothesis beyond Cycas and probably 

 Zamia, it can hardly be said to anticipate the general and 

 ingeniously supported theory of Dr. Schleiden, respecting 

 which physiological botanists are at present almost equally 

 divided. On this theory it is not ray intention at present 

 to express an opinion ; nor did the question of the mode of 

 action of the pollen form any part of my object in the pre- 

 ceding essay. I shall only here remark, that according to 

 the latest statements of Dr. Schleiden with which I am 

 acquainted,* although he admits that his investigation is 

 not in all points complete, he seems to have no doubt that 

 his theory of the origin of the vegetable embryo in the 

 pollen tube is applicable to Coniferce. He has in the first 

 place ascertained the existence of my areolae or corpuscula, 

 which he denominates large cells in the embryo-sac or 

 albumen, in all the European genera of Coniferce -^ and in 

 Abies ewcelsa, Taxus baccata, and Jtmiperus Sabina, he 

 states that he has succeeded in preparing free the whole 

 pollen tubes from the nucleary papillae to the bottom of 

 the corpuscula. But as (if my observations are correct, 

 and they seem to be confirmed by those of M. de Mirbel) 

 the corpuscida are not developed in Pinus, as the genus is 

 at present limited, until the spring or even beginning of 

 summer of the year after flowering, and if Dr. Schleiden's 

 statement be also correct, the pollen must remain inactive 

 for at least twelve months. 



The quiescent state of pollen for so long a time is indeed 



1 PhilosopMcal Transactions, vol. xxiii, part 2, n. 287, p. 1474. 



Mem. de 1'A.cacl. des Sc. de Paris, 1711, p. 210. 

 3 Anat. of Plants, p. 2. " Schleiden, Grund. der Bot, 2 Thei), p. 374. 



^ Op. cit. pp. 354 et 357. 



