No. 596] NOTES AND LITERATURE 



511 



should also determine the position of chromosome reduction to be 

 at the first mitosis of the zygote nucleus. The cystocarps of these 

 plants would then be interpreted not as a diploid sporophytc 

 generation but as a special haploid phase and the carpospores 

 would have the same value as monospores. There would he no 

 antithetic alternation of generations in such forms of the red 

 alga\ Svedelius proposes the term haplobiontic for red alga? 

 with this type of life history to be contrasted with Mplobiontic 

 forms . I'n! nsi i,h,niui, L'hnJunn hi. Crifliihsm. and I h h s« ri<t < 

 where the gonimoblasts have been shown to he diploid in charac- 

 ter and chromosome reduction finds its place in the terasporan-ia 

 of an asexual generation. The diplobiontic type of life history is 

 naturally conceived by Svedelius to arise from the haplobiontic 

 by a delaying of the reduction divisions so that <ronimohla>ts 

 carry forward the diploid number of chromosomes to the carpo- 

 spores. The carpospores being diploid develop an asexual •rcne- 

 ration and their diploid sporangia becoming the seat of the re- 

 duction divisions take the characters of tetrasporangia, a new 

 type of reproductive organ. The occasional suppression of re- 

 duction divisions in the tetrasporangium may be expected at 

 times to transform this cell to a monosporangium, as in Nito- 

 phi/llinn. showing close analogies between the two structures. 



In connection with the conclusions of Svedelius on Scinaia it 

 should be remembered that Allen has placed the reduction period 

 in the life history of Coleochwte at the first mitosis of its zygote 

 nucleus. If this view is correct the cellular body developed in 

 the oospore of Coleochcete, preliminary to the formation of a 

 crop of zoospores, is a special haploid structure and may be 

 compared with the gonimoblastic development in Scinaia as in- 

 terpreted by Svedelius. The haplobiotic red algae of Svedelius 

 then, if clearly established, would have the same type of life his- 

 tory as Coleochcete and bearing in mind the resemblance of the 

 young oogonium of Coleochcete to a carpogonk 

 the resemblance of its antheridia to a cluste 



