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 simplified gametophyte. No further 

 divisions occur in the oogonia. In some of the Fucaceae 

 (e.g., 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 greatly reduced male gameto- 

 phyte. 



222. Simplification of the Gametophytes. The im- 

 portant point to note in connection with the life history of 

 Ascophyllum is, not only the great simplification of the 

 gametophyte, but the fact that it is reduced to 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 



