815 



projected beyond the cells forming the single coat of the ovule, and 

 consisted of a large central cell (the embryo-sac) enclosed by a layer 

 of very delicate cells of small size, constituting a proper coat of the 

 nucleus. On the 9th, the ovules of fully-expanded flowers were not 

 much altered, except in the much clearer definition of the walls of the 

 cells. The embryo-sac was filled with a clear colourless fluid, in 

 which floated minute black atoms. In some flowers the stigma was 

 smeared with pollen, which sent down numerous tubes, about ^-inrsth 

 of an inch in diameter, and at most one-fourth of the size of the small- 

 est surrounding cells. On the 13th, when the flowers were withered 

 and the stigmas were covered with pollen, a dense bundle of tubes lay 

 in the midst of the lax tissue of the canal leading to the cavity of the 

 ovary. Some of the ovules were completely anatropous, while others 

 were about three-fourths curved, the forming being about T ^oth of an 

 inch in length. The two coats of the ovule were now distinctly evident, 

 and the nucleus was still covered by its own cellular coat, and still 

 contained only the clear colourless fluid with black points. On the 

 16th, the pistillary cords extended nearly to the base of the ovary, 

 presenting all the characters of pollen-tubes, and apparently continu- 

 ous with those derived from the pollen on the stigma. Both coats of 

 the ovules had become considerably developed, and the inner had 

 grown up far beyond the nucleus ; the embryo-sac had lost its proper 

 cellular coat, had acquired the aspect of a large ovoid sac attached by 

 a pedicle to the chalazal region, and contained opalescent mucilagi- 

 nous matter (protoplasm), in most cases accumulated at the ends, 

 chiefly at that next the micropyle. On the 20th, the last-mentioned 

 appearance continued ; and at the micropyle end, one, two or (usually) 

 three minute vesicles had been formed, always seeming to originate 

 as cavities in the mucilage, and not as if derived from the formation 

 of a membrane on the outer surface of a nucleus or cytoblast. These 

 vesicles soon took the apperance of distinct cells with exceedingly 

 delicate walls, and undoubtedly existed before the pollen-tubes entered 

 the foramina of the ovules. In those ovules which had been pene- 

 trated by the pollen-tubes, these were traced by Mr. Henfrey through 

 the wide mouth of the outer coat and the narrow canal of the inner, 

 as far as the apex of the embryo- sac, which however they never en- 

 tered, but generally appeared to be directed a little to one side and to 

 lie in contact with its outer surface, just over the place where the mi- 

 nute vesicles lie within. On the 31st, the previous observations were 

 repeated and confirmed on specimens in various stages of growth. 

 At this period, in some of the embryo-sacs one of the vesicles had 



