260 Mr. J. S. Sandersou on the Embryogmy 



bryogeny. We shall see as we proceed, that we are now enabled 

 to construct a morphological type of development complete in all 

 its parts, and applicable to all the hitherto investigated orders of 

 phanerogamous plants. 



Hippwis vulgaris belongs to the natural order Halorageaceay 

 which contains only three British genera, Myriophjllum, Hip- 

 puris and Callitriche, all the species of which are water-plants 

 with floating and submerged leaves. They appear to be distin- 

 guished by their submerged leaves possessing distinct bundles 

 of spiral vessels, a fact which may be well seen in the common 

 Callitriche verna^ and has been lately shown by Barneoud in those 

 curious plants the Trapas which float on the rivers of Southern 

 Europe, and are considered by many botanists as belonging to 

 this order. 



The ovary of Hippuris is one-celled, containing a single pen- 

 dulous ovule, attached nearly at its apex by a fleshy funiculus. 

 In its earhest condition I have not had an opportunity of ex- 

 amining it. If however it be examined at a period considerably 

 before that of impregnation and before the development of the 

 solitary anther is completed, it is observed to have become com- 

 pletely anatropous. The nucleus lies loosely in the cavity fonned 

 by the envelopes, which completely surround it, attached to the 

 chalaza. The envelope is not distinguishable into primine and 

 secundine, and extends considerably beyond the apex. It con- 

 sists of small hexagonal cells arranged in series, each containing 

 a nucleus. On one side, the raphe, consisting of a bundle 

 of imperfect spirals, is seen passing from the hilum to the 

 chalaza. 



The nucleus, the structure of which cannot be seen on account 

 of the opacity of the envelopes without dissecting it out, consists 

 of a large cell, the embryonic vesicle, extending from its apex to 

 about two-thirds of its length, which is surrounded by a single 

 layer of very transparent, gelatinous-looking nucleated cells, 

 which are however deficient at the apex, at which point the em- 

 bryo-sac seems to be totally uncovered. 



Contained in this embryo-sac is seen the embryo-vesicle. This 

 body consists of a single elongated cell attached to the free ex- 

 tremity of the embryo-sac. This cell (the embryo- vesicle) con- 

 tains a granular protoplasm in which here and there globules are 

 observed to float. It probably originates at a very early period 

 from the micropyle-end of the embryo-sac, but I have not been 

 able to trace it at any earlier stage than that represented. The 

 form which it presents, of an elongated cell attached to the end 

 of the embryo-sac next the micropyle, and smaller at its attached 

 than at its free extremity, is prevalent throughout the Scrophula- 

 riacea, Cruciferep, and other orders. 



