120 REPORT — 1851. 



the acceptance of tlie hypothesis of sexuality in the Vascular Cryptogams 

 as the most satisfactory explanation of the phsenomena 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 pre- 

 ceding statements, viz. 1. The late discovery of two forms of organs in the 

 Algse, 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 phaenomena 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 phy- 

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

 of the lower forrn^ of the two kingdoms, there seems far sounder ground 

 than is allowed by Schleiden for arguing from apparent analogies between 

 the phasnomena 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, Hepaticae, Ferns, and Equisetaceae agree with the 

 small spores o£ 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 Hepaticae agree with the so-called " ovules " of the Ferns, 

 EquisetacCcE, Lycopodiacesc, Isoetacea?, aiid Rhizocarpese, in general struc- 

 ture and in the presence of the central large cell from which the new form 

 of structure originates. 



The great difTerences depend on the position in time and space of the or- 

 gans, in the different classes, and the nature of the immediate product of the so- 

 called " embryo-sac," the large central cell of the pistillidia and " ovules." 



In the Mosses and Hepaticas 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 fertilization take place here, we may re- 

 gard the antheridia and pistillidia as analogues of the anthers and pistils of 

 flowering plants, the sporangia of their fruits; or with Hofmeister we may 

 regard the phaenomenon as an instance of an " alternation of generations," 

 where the pistillidium would be looked upon as an ovule, producing (in the spo- 

 rangium) a new individual of totally different character from that developed 

 from the spore (the leafy Moss plant in the usual acceptation of the term). 



In tlie Ferns and Equisetaceae, we find the spores producing a frondose 

 structure of definite form, upon which are developed antheridia and pistil- 

 lidia, or " ovules." Here then we seem to have one generation complete, and 

 the new development from the pistillidium or " ovule " appears in a totally 

 new form, producing stem and leaves which have a distiyct individual form 

 and existence, and produce the spores after a long period upon tem])orary 

 parts of the structure, on the leaves ; and by no means cease to exist when 

 those are matured. Here we seem to have a real " alternation of genera- 

 tions," and Hofmeister compares the whole permanent plant of the Fern or 

 Equisetum to the sporangium of the Mosses and Hepaticag. In all the 

 other families, the Lycopodiaceae, Isoetaceae, the Rhizocarpeae, the p ro 

 embryo is a very transitory production, and is developed from a differ en 

 spore from the spiral filaments. This pro-embryo is clearly analogous to 



