852 



Myosotis palustris. — At the time of fecundation the ovule is of a 

 globular form, with a bent cylindrical neck, at whose extremity is the 

 micropyle, (see fig. 1 and 2, p. 850). It has some resemblance to a 

 chemical retort, and its neck being turned to the base of the style, the 

 micropyle is placed apparently in immediate contact with the con- 

 ducting tissue. As the ovule advances towards maturity, the micro- 

 pyle is gradually withdrawn and elevated, until it is ultimately found 

 near the summit of the ovule, (fig. 3, c). The embryo {d) has not been 

 observed in its earliest stage, and it would be scarcely possible to 

 trace the pollen-tube, on account of its excessive tenuity, into a mi- 

 cropyle thus situated : the pollen-grains of this plant are unusually 

 diminutive. 



Nuphar lutea. — In this plant the embryo-sac is remarkable for its 

 great length, compared with that of the fully-developed embryo, which 

 occupies only a small space at the top of the ripe seed, while the em- 

 bryo-sac extends throughout its whole length. There is also a con- 

 siderable thickness of the tissue of the nucleus interposed between 

 the summit of the embryo-sac and the micropyle, at the time of fecun- 

 dation, (see fig. 4) ; tending to show that fecundation may take place 

 along the vascular tissue of the funiculus, and through the base of the 

 ovule. It seems at least probable that the nutriment of the embryo 

 is conveyed by that channel, (see fig. 5). At fig. 7 is shown an actual 

 dissection of the embryo-sac, with the primary utricle [c) in a very 

 early stage ; and another, more advanced, is exhibited at fig. 8. In 

 this the embryo [d) appears in its earliest intelligible state : when 

 fully developed, it occupies the whole of the dilated head of the em- 

 bryo-sac (c), and also assumes the same shape. The true structure 

 of the embryo has been a subject of debate, but the section at fig. 9, 

 leaves very little room to doubt that it is dicotyledonous. 



Nymphcea alha. — In this the parts are quite analogous to the last, 

 but with several modifications. Here the secundine projects very 

 much beyond the primine, and the nucleus is likewise attenuated at 

 the apex, so as almost to project beyond the micropyle. The funi- 

 culus also expands into an arillus, completely investing the ripe seed, 

 (see fig. 10 and 11). W. Wilson. 



Orford Mount, Warrington, 

 December 2, 1843. 



