26:^ Mr. J. S. Sanderson on the Embryogemj 



scribed in Hippuris is that which holds universally thronghout 

 phanerogamic plants. The results of Hofmeister, as detailed in 

 his Monograph on the origin of the vegetable embryo, published 

 at Leipzig last year, are as follows : — 



A long time previous to the period of fecundation a certain 

 number of free cellular nuclei are formed in the embryo- sac. 

 These generally occur at the end of the sac next the micropyle. 

 After this, free spherical cells are observed to be formed at the 

 same part of the embryo-sac, which are usually three in number, 

 an arrangement which probably depends on merely mechanical 

 causes, and is well seen in the Orchidacece. 



These cells are destined for the formation of the embryo itself, 

 and are to be distinguished from those of a smaller size which 

 are often observed at the same period at the opposite extremity 

 of the embryo-sac, and conduce merely to the formation of the 

 endosperm. 



These cells are the embryo -vesicles, and from them the em- 

 bryo is produced. One of them only remains active, while the rest 

 abort. This being acted on by the fovilla at the period of fecun- 

 dation, undergoes the development detailed below and becomes 

 the embryo. 



At the period of impregnation the pollen-tube an*ives at the 

 embryo-sac. Sometimes the sac-membrane is so firm as not to 

 be indented by it. Sometimes it is considerably indented, and 

 adherent for a longer or shorter period. At other times it ap- 

 pears, from its great tenuity, to be pierced by it. In all cases the 

 embryo-vesicle remains perfectly closed, so that any communi- 

 cation between it and the end of the pollen-tube is impossible. 



After impregnation the embryo-vesicle becomes divided into 

 two cells by a transverse septum. These two cells are the first 

 of those which form what Hofmeister calls the pro-embryo. The 

 distal cell then in most cases divides by horizontal septa into a 

 row of smaller cells. The terminal cell of this row then becomes 

 more developed than the rest, and gives birth by an endogenous 

 process to the embryo-globule. This then becomes developed 

 into the embryo by the successive formation of new cells. 



These results will be seen to harmonize perfectly with what 

 has been already said with reference to Hippuris. They were 

 obtained from the examination of a very great number of species 

 belonging to various natural orders ; among which may be men- 

 tioned Orchidacece, GraminecB, Liliacece, Iridacece, Amanjllidacece, 

 Polygonacea, Caryophyllacea, Ericacece, Geraniacea, &c., and there 

 is every reason to depend on their accuracy. 



In the last two numbers of the * Annales des Sciences Natu- 

 relles/ which have only appeared in the course of last week, 

 M. L. R. Tulasne has published the most complete and beautiful 



