CONTRIBUTIONS TO VEGETABLE EMBRYOLOGY. 139 



tively large size, which render the individuals of this family, as well as 

 the allied Geraniaceee, peculiarly fitted for the purpose. He arranges 

 his observations under seven general heads corresponding with as many 

 progressive periods in the growth of the female organs, and extending 

 from the completion of the anatropous development of the ovule to the 

 perfect formation of the embryo ; or from the commencement of the 

 expansion of the bud to the complete formation of the fruit. The re- 

 sults are collected from a great number of dissections. 



In the first period, or just before the expansion of the bud, a longi- 

 tudinal section of the carpellum from its dorsum towards the axis of the 

 pistillum, dividing the ovule, shows the latter to have completed its 

 anatropous development. A portion of rather firm and dense cellular 

 tissue enclosing a bundle of vessels descends from the placenta and in 

 apposition with it to form the raphe, and terminates in the base of 

 the "ovule. The nucleus has only one integument, at the apex of 

 which is the exostome or micropyle, opening close by and to the out- 

 side of the point of attachment ; and the conducting tissue of the 

 style may be traced into the carpellary cavity as far as the exostome. 



In the second period, during which the expansion of the bud and the 

 dehiscence of the anthers commence, and therefore before impregnation, 

 a small elliptical cavity makes its appearance near the apex of the nu- 

 cleus, having a delicate lining membrane formed by the walls of the 

 surrounding cells : this cavity is the embryo-sac, and a minute canal 

 may be traced leading from it to the exostome. The apex of the 

 embryo- sac encloses at this period a quantity of organizable mucilage 

 containing many minute bodies having the appearance and character of 

 cytoblasts. 



In the third period, the apex of the nucleus and of its integument 

 becomes slightly inclined towards the placenta. The embryo-sac is 

 much enlarged and lengthened; its mucilage has disappeared and 

 given place to an elongated diaphanous utricle (utricule primordiale, 

 Mirbel; vfaicule embryonnaire, Meyen; extrmit& antfrieure du boyau 

 pollinique, Schleiden ;) containing a quantity of globular matter or cy- 

 toblasts. This primary utricule is developed wholly within the embryo- 

 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 fovilla with its granules 

 is found abundantly in the passage leading from the style to the exos- 

 tome. With the increased development of the embryo- sac, the primary 

 utricule elongates and becomes distinctly cellular by the development of 

 minute cells in its interior, while at the extremity next the base of the 



