ZOOLOGY AND BOTANV, MICROSCOPY, ETC. 321 



Scinaia furcellata.* — N. Svedelius publishes an account of the 

 cytological development of Scinaia furcellata as a contril)ution to the 

 subject of reduction-division of the non-tetrasporiferous Floridete. He 

 describes the vegetative structure, the monospores, the spermatia, the 

 cystocarp with the anomalies of its development, and compares the 

 alternation of generations in Scinaia and PolysipJionia — the haplobiontic 

 and the diplobiontic Florides. He summarizes his work as follows : — 

 A study of the development of the epidermal tissue of S. furcellata 

 shows that the cells, full of protoplasm, which lie between the empty 

 epidermal cells and have been regarded as assimilation cells, are in 

 reality stalk-cells either for monosporangia, or for spermatangia, or for 

 hairs. Onlv after these growths have fallen off do the stalk-cells 

 possibly become transferred into empty epidermal cells. 



Monosporangia occur on monoecious individuals of Scinaia of much 

 the same structure and appearance as in other Nemalineae, e.g. Batracho- 

 spermum. One or two arise from the same stalk-cell. Subsequent 

 growth through a sporangium is common ; the chromosome number of 

 the monospore is approximately ten. 



The spermatangium mother-cells of Scinaia appear several together 

 in branched groups from the same stalk-cell. The spermatium nucleus 

 has ten chromosomes. 



The three-celled carpogonial branch forms, from the upper first cell, 

 the carpogonium and trichogyne, with its special nucleus. From the 

 hypogynous second cell arise, before fertilization, four auxiliary cells 

 with rich protoplasmic contents. From the lowest or third cell of the 

 carpogonial branch arise the cells which form the covering or wall of 

 the cystocarp after fertilization. The nuclei of the carpogonial branch, 

 including the egg-nucleus, have ten chromosomes. After fertilization 

 the diploid nucleus, which now has twenty chromosomes, moves into 

 one of the auxiliary cells, which fuse more or less with one another. 

 This procedure has been recorded in Gelidiacese, but not hitherto in 

 Chastangiaceae. The first division of the diploid nucleus is a reduction, 

 preceded by a short spirem stage and a distinct diakinesis with ten 

 double chromosomes. As a result there arise four nuclei. From one 

 only of these is developed the gonimoblast, which grows out from the 

 auxiliary cell into the empty carpogonium again, from which later the 

 gonimoblast branches grow out one-sidedly. The nuclei of the young 

 gonimoblast filaments have ten chromosomes. 



The wall of the cystocarp arises exclusively from the basal third cell 

 of the carpogonial branch. The cell mentioned by Setchell as bearing 

 the cystocarp is not formed from the carpogonial branch itself, but 

 from the cell in the intermediate tissue of the Scinaia thallus which 

 bore the carpogonial branch. The carpospores are cut off successively, 

 2-;]— 4 at a time. Some of the gonimoblast branches remain sterile and 

 form a sort of long paraphysis. The number of the chromosomes in the 

 carpospore nucleus is ten. Scinaia (and possibly Nemalion) represents a 

 special type of alternation of generations among the Floridese, the dis- 

 tinguishing mark of which is that the first division of the diploid nucleus 



* Nov. Act. R. Soc. Sci. Upsala, ser. 4, iv. No. 4 (1915) 55 pp. (figs, iu text). 



