1849.] Linnean Society. 27 



cause he believes that in the present state of the question all evidence 

 derived from careful observation is of some value, and partly because 

 he has succeeded in obtaining a more complete series of figures 

 illustrating the successive conditions of the ovule than has yet been 

 published ; Mohl, who gives the most complete account of the deve- 

 lopment in Orchis Morio, having given no drawings. In the first 

 stage, examined on the 3rd of May, the ovules of flowers which were 

 just opened and were without signs of pollen on the stigmatic sur- 

 face, were just curving over towards the anatropous position ; the 

 nucleus 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 dehcate 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 nume- 

 rous tubes, about ^^-gth of an inch in diameter and at most one- 

 fourth of the size of the smallest 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 former being about y^th 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 pistil- 

 lary cords extended nearly to the base of the ovary, presenting all 

 the characters of pollen-tubes, and apparently continuous 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 mucilaginous 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 surfafce of a nucleus or cytoblast. These 

 vesicles soon took the appearance of distinct cells with exceedingly 

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



