ON THE HOMOLOGIES OF THE SUSPENSOR. 59 



tected among the lower Cormophytes. Eecent embryological 

 iiivestigatious suggest, however, that the suspensor of the higher 

 members of this group is not so completely isolated an organ as 

 at first sight it appears to be, but that true homologues of it are 

 to be found in the developing embryos of the lower. A com- 

 parison of the principal facts in the embryology of different 

 members of the group of Cormophytes will, I think, suffice to 

 show that there is ample evidence for the support of this view. 



The development of the suspensor in the embryo-sac of an 

 Angiosperm may be briefly described as follows.^ As a conse- 

 quence of fertilisation the germinal vesicle (oosphere — central 

 cell) is divided, as a general rule, by a horizontal wall into two 

 cells, a superior and au inferior. The upper of these two cells 

 is attached to the wall of the embryo-sac, and undergoes numerous 

 divisions, both transverse and longitudinal, in consequence of which 

 it gives rise to a mass of tissue of an elongated form, the suspensor, 

 which bears at its inferior end the embryo which has been formed 

 from the lower of the two cells into which the germinal vesicle pri- 

 marily divided. In that portion of the suspensorwhich immediately 

 abuts upon the embryo a large well-defined cell is formed, which 

 is termed the hypophysis, and which, by repeated division, gives 

 rise to the tissues which complete the layers of that portion of the 

 embryo from W'hich subsequently the primary root is formed 

 (fig. 1, A, B, c). 



This account is generally applicable to the process of develop- 

 ment in all Phanerogams, Modifications of the process certainly 

 occur in various plants. In the Grasses, for instance, the suspensor 

 consists of a mass of cells, which is larger, in the early stages, 

 than the embryo itself, and to its apical portion the special name 

 has been given of '^embryonic appendage.^'' [Keimanhang , Hans- 

 tein.) 



It may be generally concluded, therefore, that it is from the 

 superior {i.e. the one nearer the micropyle) of the two cells 

 formed by the division of the germinal vesicle that the suspensor 

 is derived, and further, that the lowest cell of the suspensor, the 

 hypophysis, contributes to the embryo the tissues which go to 

 form its primary root. 



We may now pass on to consider the embryology of the Conifers, 

 as being a group representative of the Gymnosperms, which will 

 befound to differ inmanyimportant respects from thatof theAngio- 

 sperms. In so doing it will be advisable at the outset to accept the 



* The facts here mentioned are based upon the following researches : — 

 Hofmeister, 'Entstehung. d. Enib. d, Phanerogamen,' Leipzig, 1S49. Id., 

 "Neuere Beobacbt.,'' in Priugsheim's Jahrbiicb., vol. i, 1858. Hanstein, 

 ' Botaniscbe Abhandlungen,' vol. i, 1870. rieischer, 'Beit, zur Embryo- 

 logie,' Regensburg, 1874. 



