. The algae. Algae. EUPHYCOPHYTA 179. 20- 15- 10- 5 _fi^ult$ sterile whilst attempts to produce hybrids by artificial fertilization have so far met with no success. Schreiber (1930) found that the ratio of male to female gametophytes was always 1:1, and he subsequently showed that of the thirty-two zoospores produced in each spor- angium, sixteen gave male and the other sixteen female gametophytes. The male gametophyte of L, reli- giosa is reported to bear unilocular and plurilocular sporangia, but this is so abnormal and has never been confirmed or reported for any other species, that it can
. The algae. Algae. EUPHYCOPHYTA 179. 20- 15- 10- 5 _fi^ult$ sterile whilst attempts to produce hybrids by artificial fertilization have so far met with no success. Schreiber (1930) found that the ratio of male to female gametophytes was always 1:1, and he subsequently showed that of the thirty-two zoospores produced in each spor- angium, sixteen gave male and the other sixteen female gametophytes. The male gametophyte of L, reli- giosa is reported to bear unilocular and plurilocular sporangia, but this is so abnormal and has never been confirmed or reported for any other species, that it can hardly be accepted without further evidence. The ova of L. saccharina are re- ported to be capable of producing dwarf filamentous diploid plants which reproduce by means of unilocular sporangia. If this is confirmed it may be that here we have an example of a reversion to a primitive filamentous diploid pro- genitor, a feature which might help considerably in indicating their Fig-10° Laminaria A, L. digitata, '' ^ marked thallus before growth in ancestry. summer. Bj L. digitata, marked thal- The most important character- lus after growth in summer. C, effect . 01 ^ i_ ^- of temperature on fruiting of game- istics of the gametophytic genera- tophytes in L. digitata. After tion are: Schreiber.) (i) The male gametophyte always has smaller cells. (2) The male gametophyte always consists of more than three cells whereas the female may consist of only one cell, the oogonium. Under good nutrient conditions both become much branched. (3) The antheridia are unicellular and produce only one antherozoid. (4) Any cell of the female gametophyte may function as an oogonium. (5) The male gametophyte degenerates after the gametes are shed whereas the female gametophyte persists. The young sporophyte first produces numerous rhizoids of limited growth, but these are later covered by a disc-shaped ex- DEC. JAN Please note that these images are extracted from scanned page images that may ha
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Keywords: ., bo, bookcentury1900, bookcollectionbiodiversity, booksubjectalgae
