120 



the affinity which exists between Lycopodium and Isoetes ; 

 and since in Isoetes the sporangia do not stand isolated in the 

 axis of the leaf but upon it; since further in Psilotum, and more 

 evidently in Tmesipteris, the sporangium is situated on the 

 leaf, it becomes probable that the axillary position of the spo- 

 rangia in Lycopodium also is merely apparent, and that they 

 are rather a product of the leaf than of the stem. Yet these 

 statements are merely ventured as suppositions, for M. Mohl 

 found that the base of the sporangium is connected with the 

 midrib of the leai^ in whose axis it is situated, as well as with 

 the stem, so that we remain in doubt respecting its true point 

 of insertion. Moreover the sporangium of Lycopodium may 

 be much better compared to that of Botrychium, both in re- 

 ference to the form and to the mode of bursting than to the 

 carpel of phaenogamous plants. 



After these researches, the question should be asked: 

 whether the sporangia of the higher Cryptogamia can be re- 

 garded as the same organ as the anthers in Phanerogamia, 

 and the spores as the same organ as the pollen grains. This 

 view was already advanced for various Cryptogamia by the in- 

 genious Agardh, and founded indeed on the mode of germina- 

 tion of the sporidia, in which a similar process was supposed 

 to be recognized as at the formation of the pollen tube. M. 

 Mohl has already previously contested this view, but thought 

 that the growth of the pollen tube was a mere mechanical act 

 produced by the endosmosis and the peculiar structure of the 

 poUen grain. These tubes were said to be projected both 

 in pollen grains, which had been dried for years, and in fresh 

 ones, when moistened by acids and alcohol, statements which 

 were adopted by almost all botanists, but the incorrectness of 

 which I demonstrated ten years ago, and at the same time 

 proved, against M. Brongniart's view, that the pollen tube did 

 not arise from a mere expansion of the inner membrane of the 

 pollen, but from actual growth. 



An elaborate and highly important memoir by Dr. Schleiden* 

 is closely connected with the preceding one ; the author com- 

 mences with the admonition that the doctrine of the metamor- 



* Einige Blicke auf die Entwickelungs-Geschichte des vegetabilischen 

 Organismus bei den Phanero^amen. Wiegmann's Archiv. [An English 

 translation of the entire memoir appeared in the February and March Num- 

 bers of the London and Edinburgh Philosophical Magazine. W. F.] 



