DIVISION II. 

 COURSE OF DEVELOPMENT OF FUNGI. 



CHAPTER IV. Introduction. 



Section XXXII. There can be no question that the course of development of 

 Flowering plants, Pteridophytes, Mosses, and most of the better-known groups 

 of Algae is very nearly alike, in spite of all the multiplicity of detail and all the 

 variety exhibited by the extreme forms in these great groups of the vegetable 

 kingdom. In Ferns and Mosses where it is most absolutely differentiated two stages 

 alternate periodically in each species; one of these takes its origin from the spore 

 and ends with the formation of antheridia and archegonia, while the other is the 

 regular product of the oosphere of the archegonium and ends with the formation of 

 spore-tetrads. However much in the above-named classes the equivalent chief 

 stages, that which produces archegonia and that which produces spores, may differ 

 from one another in conformation, differentiation, and physiological character, it 

 is quite evident that they agree together in the chief points here .briefly indicated 

 and in several matters of detail. Suppose the paths pursued by the development in 

 the species to be laid down as similar geometrical figures, then the several similar 

 members, the archegonia, spores, &c. will occupy corresponding sections in the 

 figures. Members and stages of the development in different species, which thus 

 correspond to one another, are said to be homologous. The view that homologous 

 members of different species are the result of modifications of a member of an 

 ancestral type is based on the theory of descent. The phylogenetic or ' natural ' 

 affinities of a species are proved by demonstrating the homologies. 



It is an accepted truth, which therefore does not require a formal demonstration 

 in this place, that strict homologies may be shown to exist between Ferns and Mosses 

 on the one hand and Phanerogams on the other, and that these homologies imply 

 not only phylogenetic affinity, but also that agreement in the periodic succession of 

 the two main stages, or we may say in the general rhythm of the development in 

 the different species, to which attention has just been called. The same may be 

 said of relations of affinity between most groups of Algae and Mosses. It 

 follows that all these portions of the vegetable kingdom are closely united by 

 bonds of relationship into one large main group with a like course of development, 

 in a word into one main series of the vegetable world which then divides, in 

 accordance with special phenomena, into a few subordinate series 1 . 



It was for a long time a reasonable matter of doubt and may to some extent be so 

 still, whether Fungi are naturally related to this main group, and at what point they 



1 See Bot. Ztg. 1881, 1. 



