232 



REPRODUCTION, VEGETABLE (VEGETABLE OVUM). 



servations for the grounds on which an opinion 

 may be formed. 



53. The fifth and last variety of reproductive 

 organ mentioned above, is the basidium. 

 The Mushrooms, along with another group of 

 Fungi, which is distinguished by the possession 

 of loculate receptacles, each loculus of which 

 is lined with a hymenium, as e.g. Lycoperdon, 

 include nearly all of the genera in which it 

 occurs, and form Leveille's order, Basidio- 

 sporea3. The order is a very natural one, 

 and between it, and any of those which are 

 most closely related to it, we can find no 

 intermediate forms which at present might 

 serve as guides in comparing the reproductive 

 organs of the one with those of the other. 

 The basfdiospore is distinguished from all the 

 other acrogenous forms (stylospores, sper- 

 matia), by well-marked and easily-defined 

 characters viz. first, by its much greater 

 complexity of structure ; and, secondly, by 

 the very peculiar and uniform arrangement, 

 according to which the spores are developed 

 in fours at the summits of the basidia. 



SECOND PART. 

 HIGHER CRYPTOGAMIA AND PHANEROGAMIA. 



54. In the attempt which we have made in 

 the preceding sections to discover the order 

 of succession in which nature has arranged 

 the various families included among the 

 Algae, Fungi, and Lichens, we have en- 

 countered difficulties at every step. The 

 extension of the same inquiry to the higher 

 Cryptogamia and Phanerogamia is much more 

 satisfactory in its results. " The comparison 

 of the history of the development of the 

 leafy Mosses and Hepaticae on the one hand, 

 and of the Equisetaceae, Rhizocarpeae, and 

 Lycopodiaceae on the other," says Hofmeister, 

 " has shown the most complete correspondence 

 of the formation of the fruit of the one with 

 the formation of the embryo of the other. 

 The archegonium of the Mosses, the organ 

 within which the rudiment of the fruit 

 (Fruchtanlage) is formed, has a structure 

 altogether similar to that of the archegonium 

 of the Ferns (in the widest sense) to that 

 part of the prothallium in whose interior the 

 embryo of the frond-bearing plant originates, 

 In both of these large groups of the higher 

 Cryptogamia, we have a single cell, originating 

 freely within the larger central cell of the 

 archegonium, by the constantly repeated divi- 

 sions of which, in the Mosses, the fruit in 

 the Ferns, the leafy plant, takes its origin. In 

 both cases the division of this cell fails to 

 take place, and the archegonium aborts, if the 

 spermatic filaments (Saamenfaden) do not 

 reach it at the moment that its summit gives 

 way." * 



55. The higher Cryptogamia and Phanero- 



* Hofmeister, Vergleichende Untersuchungen der 

 Keimung, Entfaltung u. Fruclitbildung hoherer 

 Cryptogamen. p. 139. Leipzig, 1851. 



gamia form a series, which, commencing with 

 the frondose or membranous Hepaticae, ascends 

 through the Jungermanniae and Marchantiae 

 to the true Mosses. At this point, the thread 

 is interrupted, but is easily resumed, and fol- 

 lowed through the Ferns and Lycopodiaceae to 

 the Rhizocarpeas. Between these last and the 

 Phanerogamiae, there is again an interval of 

 obscurity, which is succeeded in the latter by 

 a new order of phenomena. The plants 

 belonging to the series before us are charac- 

 terised by their displaying a regular alternation 

 of two generations which differ widely in 

 their organisation. Of these, the first, taking 

 its origin from the germinating spore, develops 

 two kinds of organs, the reproductive func- 

 tions of which are complementary to each 

 other. One of these (archegonium) is destined 

 for the reception of a germ-cell, while the 

 other (antheridium) sets free a number of cor- 

 puscles closely resembling the antherozoids 

 of Chara, which have been already described. 

 It is from this germ-cell that the second gene- 

 ration commences its existence ; its develop- 

 ment being, as there is now every reason to 

 believe, dependent on the actual contact of 

 the antherozoids. It differs completely in 

 form and structure from its parent, and pos- 

 sesses only one kind of reproductive organ. 

 This organ throws off germs (spores), each of 

 which is capable, independently of any ex- 

 ternal influences, except those of heat and 

 moisture, of transforming itself into a new 

 individual. This in its turn produces pistillidia 

 and antheriditty and thus forms the starting 

 point of a new development. 



56. Supposing the history of the develop- 

 ment of the plants under consideration to com- 

 mence with the germination of the spore, and 

 terminate with its arrival at maturity, it may 

 be divided into two periods. Of these the 

 first is completed in the full development of 

 the archegonia and pistillidia, and the com- 

 bination of their products, so as to form an 

 embryo ; while the second terminates in the 

 full development and distribution of the spores. 



57. Among the lower Hepaticae, the vegeta- 

 tive system (frond) consists of a simple mem- 

 branous expansion, which may be considered 

 equivalent to what would result from the 

 soldering or fusing together of the leaves and 

 stem of a more highly developed plant. The 

 frond is of various forms always originally 

 linear, and lengthens at one (the anterior) 

 extremity only. At the other end, which is 

 eajrliest formed, cessation of vegetation, and 

 marcescence are constantly taking place. The 

 adult plant assumes very various forms, which 

 arise from the repeated bifurcation of the 

 original riband-shaped shoot. In the plant, 

 the development of which we are about to 

 describe (Anthoceros laevis) as one of the 

 most simple of the Hepaticae in its structures, 

 the fully-formed frond is a lobed expansion of 

 succulent, dark-green parenchyma, the general 

 contour of which is circular. We shall divide 

 the history of its development into two 

 periods, corresponding with those laid down in 

 the last paragraph. 



