414 IIOFMKISTER, ON 



assumed that its growth then ceased, the above pheno- 

 menon would be sufficiently explained.* 



The refractive power of the substance of the nuclei of 

 the freely-floating cells of the corpuscula of Pinus sj/Ivesfris, 

 austriaca, and Strobus, is so exactly the same as that of 

 the contents of the cells, that the nuclei do not become 

 visible until by the prolonged action of water, or of tincture 

 of iodine, the contents of the cell and of the nucleus 

 are changed, and the albuminous matter coagulated. In 

 the corpuscula of Pimcs canadensis the refractive power of 

 the nuclei upon transmitted light is greater than that of the 

 contents of the cells. 



The number of the freely-floating cells in the corpuscula 

 of the Abietinese is so great that they quite fill the latter. 

 This is the ground of the statement made by Mirbel and 

 Spach that the corpuscula are filled " par un tissu fin et 

 jaunatre/' In Taxus, Juniperus, and Cupressus, the 

 number of these cells is usually less, but yet cases occur 

 here also in which they entirely fill the corpuscula (PL 

 LXIII, fig. 11 ; PI. LXIV, fig. 1 ; PI. LXV, fig. 9). 



Of the many delicate-walled daughter-cells of the 

 corpusculum, those which occupy its upper and lower 

 end often appear to be pressed against it, in like 

 manner as the germinal vesicles of the phaenogams and 

 the cells antipodal to them press against the two ends of 

 the embryo-sac. In the upper end of the corpusculum 

 they are only found when the arch of the latter is particu- 

 larly steep, and then several usually occur (PL LXI, 

 fig. 1) ; in the lower end one only is found, and that not 

 often ; when present it is much flattened above. 



The development of the endosperm in the embryo-sac of 

 the Coniferse does not appear to be absolutely dependent 

 upon the contact with pollen of the same species, although 



* It is undeniable that many cases of free cell-formation, especially those 

 occurring in the embryo-sac of phsenogarns, when considered by themselves, 

 agree better with the theory of the identity of the cell and the nucleus, than 

 with the opposite one propounded by Schleiden. It is not so however with all ; 

 in some cases {Asphodelus albus, Staphylea pinnatd) the diameters of the cells in 

 process of formation are always at least half as large again as those of the largest 

 of the freely-floating nuclei. The undoubted analogy however with the fully- 

 observed cases of the so-called cell-division, suggests the necessary explanation 

 even of those more obscure phenomena. 



