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THE AMEBIC AX NATURALIST 



[Vol. L 



they were borne. It is probable that other red algne will exhibit 

 peculiarities of life history related to apospory, as seems prob- 

 able in this ease of Agardhiella. 



There is enough evidence before us in these three studies by 

 Y;!iii.-<nnurhi. Lewis and Swdelias to demand the utmost caution 

 in the consideration of other cases of "tetraspores" upon sexual 

 plants which have been brought forward by critics of the theory 

 of alternation of generations as applied to the red alga?, cases 

 which have not as yet been subjected to the tests of cytological 

 research. One of the most interesting of these is Platoma Bairdii 

 (Farl.) Kuckuck 11 which in Helgoland apparently produces no 

 antheridia but develops cystocarps partbenogeiietically. On 

 these cystocarpic plants are also found tetraspores indicating 

 that the plants are diploid in character which if true would ac- 

 count for their apogamous behavior. Platoma Bairdii therefore 

 appears to be one of the cases in which sexual organs are devel- 

 oped upon a diploid plant and not one in which tetraspores are 

 found on a haploid generation. A cytological study of this form 

 would be a matter of great interest and the only way in which the 

 facts may be determined. Also, there are the problems of the 

 paraspores or polyspores characteristic of a number of species in 

 the Ceramiacew. These are spores borne numerously in chains 

 (seirospores) or in dense glomerules and are found on tetrasporic 

 plants. Schiller 1 - regards them as homologous with tetraspores, 

 and as supporting the view of Oltmanns that the latter are repro- 

 ductive spores without significance for an alternation of genera- 

 tions, but until we know the cytology of their development an 

 opinion can have little value. Should the paraspores be formed 

 without reduction divisions, as seems probable, they will rank in 

 the same class with monospores and play no part in an alterna- 

 tion of generations. Should there be found evidence of a hetero- 

 typic mitosis in the development of these exceptional reproductive 

 cells they might perhaps constitute a modification of the tetrad 

 group characteristic of reduction divisions, but it does not seem 

 likely that this will prove to be the ease. 



There is left for consideration those red alga' which produce 

 no tetraspores at any phase of their life history. They include 

 a number of well-known types such as Nemalion, Batrachosper- 



11 Kuckuck, P., "Ueber Platoma Bairdii (Farl.) Kck.," Wiss. Meeres- 

 mtermuih. Biol. Anstalt Helgoland., V, 187-203, 1912. 



« Schiller, J., "Ueber Bau, Entwicklung, Keimung und Bedeutung der 

 Parasporen der Ceramiaceen, " Oester. hot. Zeitsch., LXIII, 144, 203, 1913. 



