H)0 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 



Including- the Anatomy and Physiology of Seed Plants. 



Cytology, 

 including' Cell-Contents. 



Cytology of the Pollen of the Nymphseaceae. * — W. Lubimenko 

 and A. Maige have completed their researches upon the pollen-mother- 

 cells of the Nyrnphseacese, with the following results. In the 

 prosynapsis stage there is a simple nuclear network with chromatin 

 granules ; during synapsis the nuclear membrane bursts, while the 

 network forms a spongy mass round the nucleolus, and the chromatin 

 granules fuse to form corpuscles. During the spireme stage the chro- 

 matic thread fills the nuclear cavity, but there is no longitudinal 

 splitting at this stage. 



The chromosomes are formed by condensation of the chromatin at 

 different points of the spireme. The first and second mitoses are 

 normal, but in the telophase of both, a transitory granular plate appears 

 at the equator of the spindle, which probably represents a remnant of 

 one of the ancestral divisions of the pollen-mother-cells. Also in the 

 telophase the mother-cell is simultaneously divided into four daughter- 

 cells. In this respect, the two species studied resemble the Dicotyledons, 

 while the simple nature of the prosynapsis and the early dissociation of 

 the pollen-mother-cells brings them near the Dicotyledons. There 

 appears to be a certain ratio between the masses of the nucleus and of 

 the cell, both in the vegetative and reproductive tissues, and this ratio 

 varies in a very definite way in the different cycles of development. 

 The three pollen mitoses differ from a vegetative mitosis by bringing a 

 larger mass of chromatin into play, and by the larger quantity of 

 nuclear contents, which are very rich in chromatin. The third mitosis 

 results in the formation of two nuclei, a large vegetative nucleus and a 

 small generative one ; this difference in volume may be attributed to 

 an unequal division of the chromatin in this mitosis, which would thus 

 play an important function in chromatic reduction. 



Cell and Nuclear Division in Basidiobolus ranarum.f — Edgar W. 

 Olive studied this fungus on material cultivated from the intestine of a 

 frog. He found that the processes of division were the same in both 

 beak and vegetative cells with some minor differences. Cell-division 

 takes place by the gradual growth of a cell-plate from the wall inwards 

 like the narrowing of an iris diaphragm. The mitotic figure consists of 

 a broad barrel-shaped spindle ; the chromatin plate in the centre 

 consists of a mass of numerous minute chromosomes, and at each pole 



* Rev. Gen. Bot., xix. (1907) pp. 474-501. See also this Journal, 1908, p. 60. 

 f Ann. Mycol., v. (1907) pp. 404-18. 



