220 THE ALGAE 



The antheridia are either borne scattered over the whole surface 

 (NemaUonales), or else in localized sori. These sori are reticulate in 

 Rhodymenia, band-like in Griffithsia, borne on special branches in 

 Polysiphonia, sunk in conceptacles in the Corallinaceae, and occur 

 on the tips of the thallus on Chondrus. Very little is known about 

 the seasonal periodicity of the male plants, which are often less fre- 

 quent 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 anther- 

 idia often appear in an orderly sequence, being cut off usually as 

 subterminal or lateral outgrovin:hs from the antheridial mother cell. 

 If they have been borne on a special part of the thallus (e.g. Deles- 

 seria) 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 vegeta- 

 tive cells either in form or content, nor are the antheridia 

 covered by a continuous outer envelope, e.g. Nemalioriy 

 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. Melohesia^ Holmsella. 

 (2) The antheridia develop subterminally : 



(a) Two primary antheridia, e.g. Delesseria sanguinea, Chondrus 



crispus. 

 {h) Two or three primary antheridia, e.g. Scinaia furcellata, 



Lomentaria clavellosa. 

 (c) Three primary antheridia, e.g. Ceramium rubrum, Griffith- 



sia corallina. 

 {d) Four primary antheridia, e.g. Polysiphonia violacea, Calli- 

 thamnion 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 all red algae the nucleus of the spermatium is in late prophase 

 when Uberated but normally no division takes place. In Batracho- 

 spermum and Nemalioriy however, a division does occur but only 



