No. 596] NOTES AND LITERATURE 



507 



have been reported to bear tetrasporangia on sexual plants, facts 

 which would be significant if it were established that such tetra- 

 sporangia were the seat of reduction divisions. Three of these 

 species have been studied cytologically and there is good evidence 

 that the reduction divisions are not present and that tetraspores 

 are either not fully matured or that the "tetrasporangium" 

 develops a monospore. Yamanouchi and Lewis in their studies 

 found occasional sexual plants bearing what seemed to be tetra- 

 sporangia but in these cells the nucleus remained undivided in 

 J'ohjsiphonia or produced several nuclei in Griffithsia while 

 cleavage furrows proceeded only a short distance into the cyto- 

 plasm. Svedelius 10 has reported on a cystocarpic plant of Nito- 

 phyllum punctatum bearing tetrasporangium-like structures. 

 These cells were found around points in the thallus where pro- 

 carps had been formed and only reached their fullest development 

 when the procarps remained unfertilized. Their position on the 

 thallus therefore indicated a close correlation with the nutritional 

 physiology of the plant. These cells in their early history follow 

 exactly the course of normal tetrasporangia in this species; there 

 is a multiplication of nuclei and then a degeneration of all but 

 one which takes its position in the center of the cell. The sur- 

 viving nucleus does not divide but the entire protoplast slips 

 out of the thallus as a uninucleate monospore. Since the cysto- 

 carpic plant was haploid a reduction division in this tetraspo- 

 rangium-like cell would have been most irregular; it does not take 

 place and the monospore in its chromosome count has the same 

 value as a tetraspore. Agardhiella (Rhabdonia) tenera presents 

 another problem brought forward by observations of Osterhout. 

 Tetraspores of this plant sometimes germinate while still im- 

 bedded in the tissues of the parent with the further peculiarity 

 that the tetrad group behaves as a unit so that all four cells enter 

 into the formation of a sporeling. These epiphytic sporelings 

 ccmmonly become sexual plants, as would be expected from the 

 germination of tetraspores. Osterhout, however, reports that 

 occasional tetrasporic plants are developed which would be irreg- 

 ular unless it were found that such plants came from tetra- 

 sporangia in which reduction divisions had been suppressed so 

 that such tetrasporangia, behaving like monospores, give rise to 

 diploid plants (tetrasporic) similar to the generations on which 

 10 Svedelius, N., "Ueber Sporen an Geschlechtspflanzen von Nitophyllum 

 P'i»rt„tam; ein Beitrag zur Frage des Generationsweehsels der Florideen," 

 Ber. dent. hot. Gesell, XXXII, 106-116, 1914. 



