232 Mr. II. Giraud on the recent Doctrines 



cular points upon which they do not agree, and with regard 

 to which the statements of Mirbel and Spach would appear 

 to controvert the views of Schleiden, may be ranged under 

 three general heads, corresponding with as many stages of the 

 development of the female organs. 



1st. Schleiden maintains that when the axis of the ovule 

 makes an angle of about 90° with that of the style, an oval 

 cavity, containing a limpid mucous fluid, (cambium, Mirbel,), 

 is diacow red near the apex of the nucleus; that the forma- 

 tion of this cavity is contemporaneous with that of the embryo- 

 sac (quintine, Mirbel; sac-cmbryonnaire, Brongniart,), which 

 soon makes its appearance, gradually increases, and becoming 

 filled with a cellular substance, occupies a considerable space 

 in the nucleus. Now in opposition to this, M. Mirbel's in- 

 vestigations have shown, that the little cavity, which is always 

 fixed to the apex of the nucleus, does not become enlarged 

 during the growth of the ovule ; but that its fluid contents 

 soon contribute to the formation of the primary utricle. 



2nd. It is asserted by Schleiden, that when the oval cavity 

 enlarges and the embryo-sac is correspondingly developed, the 

 tube issuing from the pollen grain penetrates to the summit 

 of the nucleus, pressing before it the membrane of the embryo- 

 sac, which, yielding to its pressure, forms a caecum in which 

 the extremity of the tube is lodged. This view is opposed by 

 the statements of Mirbel, who has shown that in many spe- 

 cies of plants, and particularly in the Gramineae, the embryo- 

 sac is wanting ; and that in these cases the primary utricle 

 takes its origin from the fluid matter (cambium) of the little 

 cavity of the nucleus ; so that this last may be wholly desti- 

 tute of a lining membrane, such as Schleiden would make the 

 embryo-sac. But even supposing that this part existed and 

 underwent the changes conceived by Schleiden, and that a por- 

 tion of the embryo-sac was expanded into a caecum serving as 

 a sheath for the extremity of the pollen tube, it would follow 

 that from the translucency of the parts, the existence of two 

 membranous expansions (the pollen tube and the embryo- 

 sac) might readily be determined; but both Mirbel andWydler 

 have only succeeded in detecting one ; that, namely, which 



