88 SUMMARY OF CURRENT RESEARCHES RELATING TO 



new) are classified under 4 subgenera, viz. Cbonantlielia (comprising 

 F. arietina only), Homotropanthe, Thiopsiella, and Diastoloba. 



Spore-mother-cells of Anthoceros.* — Mr. Bradley M. Davis gives 

 the following among the more important results of an examination of 

 the development of the spore-mother-cells in Anthoceros Isevis. The 

 number of chromosomes is 8 in the sporophyte, and 4 in the gameto- 

 phyte. The chloroplast appears rather suddenly in the spore-mother- 

 cell as a differentiated region of the protoplasm containiug several 

 starch-grains. When fully developed it has a honeycomb structure, 

 each cavity being occupied by a starch-grain. The division of the 

 chloroplast is by simple fission. Synapsis occurs in the nucleus soon 

 after the first division of the chloroplast. The second division of the 

 chloroplast presents the sporc-mother-cell ready for the division cf the 

 nucleus. The resting nucleus has a nucleole and a very small spirem- 

 thread. Prophase conditions of the nucleus show the presence of a 

 mesh of delicate fibrils (filar plasm) around the structure. The nuclear 

 membrane is at first irregularly angular, but finally two poles of a 

 spindle are differentiated. The metaphase presents a spindle with flat- 

 tened poles, but no indication of centrospheres or centrosomes. There 

 is a period of rest after the first mitosis, when each daughter-nucleus has 

 a nucleole and a spirem-thread ; the second mitosis agrees entirely with 

 the first. The chromosomes are 4 in number in each mitosis ; they 

 appear to split longitudinally. All traces of the spindle become lost 

 soon after each mitosis. The fully matured spore-mother-cell presents 

 4 chloroplasts, each with a single nucleus on the interior side. The 

 protoplasm collects in these four regions of the cell, leaving spaces that 

 are crossed by many anastomosing strands of cytoplasm. These strands 

 cannot be traced from spindle-fibres, and .'.ppear to have no connection 

 with the filarplasm. The walls separating the cell-contents into 

 4 spores are derived from films of protoplasm that appear between the 

 chloroplasts with their respective nuclei. The films are formed by the 

 coalescence of strands of cytoplasm that cross the spaces between the 

 four regions of cell-contents. 



Centrosomes in Marchantia.f— In certain cells of the gamophyte of 

 Marchantia polymorplta (e.g. the stalk-cells of the receptacle), Prof. D. M. 

 Mottier finds undoubted centrosomes, and they apj>ear to be universal in 

 the vegetative cells. By the time the chromosomes are differentiated, 

 or even earlier, the centrospheres lie nearly diametrically opposite one 

 another, and appear to be in all cases attached to the nuclear membrane. 

 As soon as the chromosomes are regularly arranged in the equatorial 

 plate, the polar radiations become faint, and soon disappear. When the 

 daughter chromosomes have arrived at the poles, and before any trace of 

 a nuclear membrane is visible, neither centrosome nor polar radiations 

 are to be seen. 



Structure and. "Development of Cryptomitrium.J — A study of the 

 monotypic Cryptomitrium tenerum leads Mr. Le Eoy Abrams to place 

 it near Buvalia among the Marchantiacese. It has minute stomates 



* Bot. Gazette, xxviii. (1899) pp. 89-108 (2 pis.). 



t Proc. Indiana Acad. Sci., 1898, pp. 16G-8. 



t Bot. Gazette, xxviii. (1899) pp. 110-21 (6 figs.). 



