84 PART 1. THE MORPHOLOGY OF PLANTS. [ 17. 



Algoe, except Characeoa ; Fucaceae), as also generally in Phanero- 

 gams. In all the other cases ifc is mnlticellular, and of simple 

 structure, except in the Characeae, where the structure is ex- 

 tremely complex. In some cases (Rhizocarps) the antheridium 

 consists almost entirely of the mother-cells of the spermatozoids ; 

 in most cases the mother-cells are surrounded by a parietal layer 

 of cells. The pollinodiuni is generally unicellular. 



The oogonium is either unicellular, as is generally the case, or 

 it is a ccenocyte (e.g. Peronosporaceae, Vaucheria). The archegoniuin 

 is generally mnlticellular, consisting of a cellular wall investing 

 the oosphere, usually prolonged into a tubular neck; but in some 

 of the higher plants, Welwitschia among the Gymnosperms, and 

 all Angiosperms, the archegonium is reduced to a single cell, the 

 oosphere. The archicarps and procarps are unicellular in some 

 cases, multicellular in others ; in most cases the organ is pro- 

 longed into a filament, the trichogyne, by means of which fertili- 

 sation is effected. The oogonia (except those of Peronosporacea?, 

 Saprolegniaceae, and Characeae) and the archegoiiia, open, so that 

 their contents are in direct relation with the surrounding medium ; 

 in the procarps and archicarps this is not the case. 



Further details are given in Part III. in connexion with the 

 plants to which the various organs belong. 



(c) The Gametophore. In some plants in which the gametophyte 

 is well-developed, the sexual organs are not borne indifferently on 

 any part of the body, but are confined to particular regions or 

 branches of the thallus or of the shoot, which may be distinguished 

 as gametophores-, as in some Algae (e.g. Himanthalia lorea}, Liver- 

 worts (e.g. Marchantia), Mosses (e.g. Sphagnum), and some Ferns. 

 In Himanthalia lorea (Fig. 44) the vegetative portion of the body 

 is conical in form and is attached at its pointed end, and from the 

 middle of the cup-like upper surface there grows a long branched 

 gametophore. In Marchantia, and some other Liverworts, some 

 of the flattened prostrate branches of the thallus develope termi- 

 nally into an erect cylindrical gametophore, bearing male or female 

 organs (antheridia or archegonia) on a receptacle at its summit. 

 In Sphagnum, also, the antheridia and archegonia are borne re- 

 spectively on distinct and specialised branches. Such unisexual 

 gametophores may be specially designated antheridiophores or 

 archegoniophores. In some Ferns which have an altogether fila- 

 mentous gametophyte (e.g. Trichomanes), the female organs (ar- 

 chegonia) are borne on short multicellular lateral branches form- 



