238 STRUCTURE AND LIFE HISTORIES 



or gametophytic generation. In other words they have 

 the same value as spores, and the one-celled stage of the 

 spermagonia and oogonia the same value as spore-mother- 

 cells. 



220. Female Gametophyte. — Each of the four cells re- 

 sulting from the reduction-divisions in the oogonial 

 protoplast divides again, producing a total of eight cells, 

 which constitute a very simple gametophyte. No further 

 divisions occur in the oogonia. In some of the Fucaceae 

 {e.g.f Fucus vesiculosus) each of these eight daughter-cells 

 functions as a female gamete or egg; but in Ascophyllum, 

 and a few other species, part of the daughter-cells, as 

 stated above, disintegrate or abort, leaving only from one 

 to five. In Ascophyllum nodosum one-half of them abort, 

 leaving only four eggs. The female gametophyte is thus 

 seen to be reduced to merely its gametes. 



221. Male Gametophyte. — Each of the four cells 

 resulting from the reduction-divisions of the spermagonial 

 protoplast undergoes four divisions in succession, re- 

 sulting in 64 cells or a total of 256, all of which develop 

 into a male gamete, or sperm. The four daughter-cells, 

 therefore represent a very elementary or simple male 

 gametophyte. 



222. Simplification of the Gametophytes. — The im- 

 portant point to note in connection with the life history of 

 Ascophyllum is, not only the great simplicity of the game- 

 tophyte, but the fact that it consists of nothing but 

 fertile or reproductive cells. Each of the four spores 

 gives rise only to gametes; no sterile cells, or gametophytic 

 plant bodies are produced. 



223. Gametophyte or Sporophyte.— In light of the facts 

 above related, the question as to the real nature of the 



