53 a 



ACROGENS. 



" 3. The direct observation of a process of fertilisation, of which we have only 

 testimony from two authors, Suminski and Mercklin, in reference to the Ferns alone ; 

 since the assertions of Schleiden in regard to the Rhizocarpese have been demon- 

 strated by Niigeli, Hofmeister, and Mettenius, to have been based on very imperfect 

 observation. 



" The circumstantial evidence furnished under the first head seems to me very 

 strong— so much so that I am inclined to adopt the idea of sexuality on this ground, 

 as the )« provisional hypothesis arising out of our present knowledge, espe- 



cially when supported so strongly as it is by the negative evidence indicated under 

 the second head. 



•' The positive evidence of the third head is certainly very insufficient as yet, con- 

 sidering the extreme delicacy of the investigation. Suminski's other observations on 

 the details havo been contested in many particulars; and Mercklin, the only other 

 observer who asserts that he has seen the spiral filaments within the so-called ovules, 

 describes the conditions differently, and states that he has only been able to observe 

 them positively there three times. At the same time the difficulty of the investiga- 

 tion should make us hesitate in attaching too much weight to the failure of the other 

 observers in tracing a process of fertilisation ; moreover, it is quite possible that 

 actual entry of the spiral filaments into the canal of the ovules or pistillidia is not 

 always, if ever, necessary. 



" The facts before us, then, appear to me strong enough to warrant the adoption of 

 the views propounded by the latest authors on this subject, and the acceptance of the 

 hypothesis of sexuality in the vascular Cryptogams as the most satisfactory explana- 

 tion of the phenomena as yet observed. The question lies now much in the same 

 condition as that of the sexuality of flowering plants before the actual contact of the 

 pollen-tubes with the ovules had been satisfactorily demonstrated. 



" Further arguments may be adduced from grounds lying out of the preceding 

 statements, viz., 1. The late discovery of two forms of organs in the Alga?, Lichens, 

 and Fungi, which, although imperfect at present, lead to the expectation that the 

 analogues of the antheridia and pistillidia of the Mosses, so long known, will be found 

 in all Cryptogamous plants. 2. The analogies between the processes of animal and 

 vegetable reproduction which appear to be offered by these new views of the nature 

 of the phenomena in the vascular Cryptogams. To this last argument I shall merely 

 allude, as it may be considered to lie beyond the special province of the vegetable 

 physiologist ; yet when we recollect the imperceptible character of the gradations of 

 the lower forms of the two kingdoms, there seems far sounder ground than is allowed 

 by Schleiden for arguing from apparent analogies between the phenomena occurring in 

 the two great kingdoms of nature. 



"Under the second point of view mentioned above, the facts of structure may 

 soon be disposed of, so far as the analogies of form are concerned ; the antheridia of 

 the Mosses, Hepaticrc, Ferns, and Equisetacea?, agree with the small spores of Isoetes, 

 Selaginella, Pilularia, and Salvinia, in producing the cellules in which are developed 

 the moving spiral filaments which constitute the essential character of the organs of 

 the one kind ; while the pistillidia of the Mosses and Hepaticse agree with the so-called 

 ' ovules ' of the Ferns, Equisetacete, Lycopodiacese, Isoetacese, and Rhizocarpea?, in 

 general structure, and in the presence of the central large cell from which the new 

 form of structure originates. 



" The great differences depend on the position in time and space of the organs, in the 

 different classes, and the nature of the immediate product of the so-called ' embryo- 

 sac,' tho large central cell of the pistillidia and ' ovules.' 



" In the Mosses and Hepaticse the pistillidia occur upon the plant when the vegetative 

 structure is perfect, — and the immediate product of the great cell is a sporangium. 

 If a process of fertilisation take place here, we may regard the antheridia and pistil- 

 lidia as analogues of the anthers and pistils of flowering plants, the sporangia of their 

 fruits; or, with Hofmeister, we may regard the phenomenon as an instance of an 

 ' alternation of generations,' where the pistillidium would be looked upon as an ovule, 

 producing (in the sporangium) a new individual of totally different character from 

 that developed from tho spore (the leafy Moss plant in the usual acceptation of the 

 term). 



" In the Ferns and Equisetacea?, we find the spores producing a frondose structure 

 of definite form, upon which are developed antheridia and pistillidia, or 'ovules.' Here 

 then we seem to have one generation complete, and the new development from the 

 pistilliilium or 'ovule' appears in a totally new form, producing stem and leaves 

 which have a distinct individual form and existence, and produce the spores after a 

 iong period upon temporary parts of the structure, on the leaves; and by no means 

 ■ exurt when those are matured. Here we seem to have a real 'alternation 



