CHAPTER IV. INTRODUCTION. 121 



comparison with allied forms which are not Fungi. For the latter object it will be 

 well to recall briefly in the first instance the phenomena generally characteristic of 

 the course of development in those groups, which in a comparative account come next 

 to the Fungi, viz. the Algae, Mosses, and Ferns. It is presumed that the details, 

 for which the reader is referred to Sachs' Text-book or Goebel's Outlines of Classifi- 

 cation, are already known. 



SECTION XXXIII. In all the above groups, with some exceptions, which, 

 however, are so extremely few that they may be at first disregarded, we may set out 

 from a cell which is fertilised by the sexual act of conjugation, or from a cell-group, 

 its equivalent, which has been shown to be everywhere homologous and may 

 therefore be designated by a common name. For this name we may choose the 

 word archicarpium (archicarp\ meaning commencement of fructification, with refer- 

 ence to the evident fact that the body usually known as the fructification very often 

 proceeds from it as the immediate product of development. In the Ferns and 

 Mosses the archicarp is the oosphere in the archegonium ; in the two chief classes of 

 flowering plants it is the cells which are the homologues of the oosphere and in some 

 cases bear the same name; in the Florideae it is the procarpium (procarp), which 

 consists of a single cell or a small cell-group ; in the ovigerous Algae, as Vaucheria, 

 Chara, Oedogonium, Coleochaete, it is also a single oosphere which in this case 

 is formed in the oogonium; lastly, in the isogamous Algae, as the Zygnemeae, 

 Desmidieae, and Botrydium, it is any gamete-cell which conjugates normally with a 

 similar cell. 



If now we follow the course of development onwards from the archicarp, 

 fixing our attention first of all on the simplest cases which are confined as it were to 

 the most necessary members produced by development, we find the archicarp 

 consisting of a single *cell become under favourable conditions a spore, i.e. a cell 

 capable of growing directly into a vegetative body like the parent, and giving rise to 

 fresh archicarps as the last product of the development ; with these archicarps the cycle 

 of development begins anew. This is the history of Vaucheria aversa 1 , Chara, Fucus, 

 and Spirogyra. The case is one degree more complicated, when other conditions 

 being the same one spore is not formed directly from the archicarp, but a pluri- 

 cellular body unlike that which produced the archicarp, all or some of the cells of 

 which have the qualities of spores in the sense indicated above, and so far as this is 

 the case are capable of developing into other bodies bearing archicarps. Such a 

 body the product of an archicarp and essentially serving to the formation of spores 

 is termed a sporocarpium (sporocarp\ The Florideae and the Mosses afford excellent 

 and well-known examples of this kind. But we meet with a certain number of 

 cases of a much less marked character which form a very gradual passage to the 

 phenomena just mentioned as occurring in Vaucheria aversa and Fucus, for the ripe 

 oospheres of Coleochaete, Oedogonieae, Desmidieae, &c., which divide into many or 

 into four or only two daughter-cells developing into spores, are strictly speaking merely 

 sporocarps which have undergone successive stages of simplification in the order 

 here indicated. We may indeed say that if only two cells with the function of spores 



1 Walz in Pringsheim's Jahrb. V. 



