738 Some remarks on the development of Pollen. [Nov. 



yet known to me, but this may obviously ai'ise as well from a quater- 

 nary as a binary division of the nucleus. 



M. Mohl rejects very properly as highly improbable the opinion of 

 M. Brongniart, that the granules of the fovillaare secreted by some 

 part of the inner surface of the cells of the anther, and that they 

 reach their destination, the cavity of the inner membrane of each 

 grain, by absorption. It must, however, be remembered that M. 

 Brongniart alludes to this mode of formation and transmission with 

 considerable doubt. 



Lastly, M. Mohl notices the extreme similarity between the forma- 

 tion of the pollen and that of the sporules of the more developed 

 Cryptogamia. I am not aware who first pointed out this curious 

 analogy, which cannot well have escaped any one who has examined 

 both formations at a sufficiently early period. My first knowledge of 

 it is due to M. Mirbel, who pointed it out to me early in 1832*. 



Explanation of the figures, Plate XLI. 



1. Portion of a mass extracted from a loculus ; perianth 1 line in length. 



2. Ditto ditto ; perianth 1$ line in length. 



3. Three of the component cells of a mass ; perianth 1 f line long. 



4. Four similar cells more developed ; perianth ahout 2 lines long. 



5. Portion of a mass enveloped in its membrane, extracted from the cell of an 

 anther ; perianth 2 lines in length. 



5a. Two of the component cells detached. 



6. Four of the cells detached : (perianth 2| lines long :) viewed in different 

 aspects : — from one, three nuclei have escaped, and the fourth is half exserted. 



* Equisetacem do not, as might be supposed from their late elevation into 

 an order of Gymno&permce, differ from the higher forms of Cryptogamia in the 

 development of their sporula. The spiral fibres, as might be expected, are of 

 comparatively late appearance, and they are developed on or in a loose mem- 

 branous coat, no traces of which are to be found until the sporula have assumed 

 their proper form. The fibres subsequently, and about the time of the deve- 

 lopment of the fibres of the cells of the inner parietes of the capsules, become 

 free, the membrane to which they were attached remaining as an envelope to 

 the sporule, from which it subsequently becomes separable with facility. The 

 granules are of still later appearance. 



To the correctness of the chief portions of the above statement I can speak 

 with tolerable confidence, but I only infer that the hyaline envelope of the per- 

 fect sporule is the mature state of the tunic, to which the spiral fibres are 

 originally attached. 



There would hence appear to be no foundation whatever for the adoption of 

 the idea of the sexuality of Equisetacece, — an idea very likely to meet with advo- 

 cates from its extreme ingenuity. The analogy of the fibres or supposed fila- 

 ments is to be looked for in the elaters, and of the tunic or envelope in the 

 tunic of the sporules of many Hepaticee. 



