1842.] Linnean Society. 125 



cytoblasts. This primary utricle is developed wholly within the em- 

 bryo-sac, from which it is obviously distinct. 



The fourth period occurs after impregnation. The pollen tubes 

 do not extend into the carpellary cavity ; but the foviUa with its gra- 

 nules is found abundantly in the passage leading from the style to 

 the exostome. With the increased development of the embryo-sac, 

 the primary utricle elongates and becomes distinctly cellular by the 

 development of minute cells in its interior, while at the extremity 

 next the base of the nucleus it is terminated by a spherical mass con- 

 sisting of globular cells. The primary' utricle at this period assumes 

 the character of the suspensor (Mirbel), and its spherical extremity 

 constitutes the first trace of the embryo. 



In the fifth period the apex of the nucleus and of its integument 

 becomes more inclined towards the placenta; the spherical extre- 

 mity of the suspensor enlarges, and it becomes more evident that it 

 constitutes the rudimental embryo. In the mean time the suspensor 

 has become lengthened by an increase in the number of its cells ; 

 and its upper extremity is found to be protruded through the apex 

 of the embryo -sac, the apex of the nucleus and the micropyle. 

 From this extremity there is a considerable development of cells, 

 many of which hang loosely in the passage leading to the conduct- 

 ing tissue of the style, while the rest unite in forming a process 

 which passes down the outer side of the ovulum within the carpel- 

 lary cavity. This process is composed of from nine to twelve rows 

 of cells, and its extremity resembles in appearance and in the ana- 

 tomical condition of its cells the spongiole of a root. By a slight 

 traction of this cellular process the suspensor with the embryo may 

 be withdrawn from the embryo-sac through the exostome, thus pro- 

 ving the continuity of the process with the suspensor, and through 

 it with the embryo itself. 



During the sixth period the suspensor becomes more attenuated ; 

 and the cellular process has reached the base of the ovulum, the cells 

 of its extremity abounding with cytoblasts, which prove that it is still 

 progressing in development. The embryo also increases in size, and 

 two lateral processes are observed, which evidently form the first 

 traces of the cotyledons. 



In the seventh period all distinction between the nucleus and its 

 integument ceases, and they form a single envelope enclosing the 

 embryo-sac ; the cellular process has become so much developed, 

 that its extremity has passed round the base of the ovulum and is 

 directed towards the placenta ; and the lateral processes of the em- 

 bryo have become distinct fleshy cotyledons, enclosing both the 



