RHODOPHYCEAE 215 



when they were considered to be male by analogy. The antheridia 

 are either borne over the whole surface (e.g. Dumontia), or else in 

 localized sori. These sori are reticulate in Rhodymenia, band-like in 

 Griffithsta, borne on special branches in Polysiphoniay sunk in 

 conceptacles in Laiirencia and occur on the tips of the thallus in 

 Chondrus. Very little is known about the seasonal periodicity of the 

 male plants, which are often less frequent than either the female or 

 tetrasporic plants, but this may be due purely to lack of observation, 

 although it is also possible that the male plants are gradually 

 becoming functionless. The antheridia often appear in an orderly 

 sequence, being cut off usually as subterminal or lateral outgrowths 

 from the antheridial mother cell. If they have been borne on a 

 special part of the thallus (e.g. Delesseria) this may fall off or die 

 away after fruiting is completed, whilst in other cases the mother 

 cells simply revert to a normal vegetative state. The different types 

 of male plant have been classified by Grubb (1925) as follows: 



{a) The antheridial mother cell does not differ from the vege- 

 tative cells either in form or content, nor are the antheridia covered 

 by a continuous outer envelope, e.g. Nemalion, Batrachospermum. 

 (b) The antheridial mother cells are differentiated from the 

 vegetative cells, and the antheridia are surrounded by a common 

 outer sheath, which is later pierced by holes or else gelatinizes in 

 order to allow^ the ripe spermatia to escape : 



(i) The antheridia develop terminally, e.g. Melobesia, Holmsella. 

 (2) The antheridia develop subterminally : 



{a) Two primary antheridia, e.g. Delesseria sanguinea, Chon- 

 drus crispus. 

 (b) Two or three primary antheridia, e.g. Scinaia furcellata, 



Lomentaria clavellosa. 

 {c) Three primary antheridia, e.g. Ceramium rubrum, Grif- 

 fithsta corallina. 

 (d) Four primar>^ antheridia, e.g. Polysiphonia violacea, 

 Callithamnion roseum. 

 The primary antheridia are commonly succeeded by a second crop 

 which arises within the sheaths of the first, but a third crop only 

 occurs in a few genera. In Nemalion, after the spermatium has 

 become attached to the trichogyne, the nucleus undergoes a 

 division but only one of the daughter nuclei acts as the fertilizing 



