366 SUMMARY or CURRENT RESEARCHES RELATING TO 



Cell-nucleus in the Mother-cells of the Pollen of Liliacese.* — 

 Investigations on this point have been carried out by A. Lalewski, 

 mostly on lAlium canclidum and Allium Mohj. His mode of preparation 

 was to place transverse sections of the young stamens in a 1 per cent, 

 solution of acetic acid, slightly coloured by methyl-green. After a 

 time, the nucleus acquires a beautiful blue colour, while the remaining 

 contents of the cell continue nearly or quite colourless. 



The large and fully developed cell-nucleus of Lilium candidum is 

 enclosed, not in a pellicle of denser nuclear substance, but in an 

 extremely delicate coat of cellulose. Immediately beneath the surface 

 it usually contains a finely granular semi-transparent nucleolus, which 

 is not coloured by methyl-green, and which remains unchanged up to 

 a certain period in the division of the nucleus. After the initial 

 stages, the membrane of the nucleus is resorbed, the vermiform 

 structures which had been formed become straight, and place them- 

 selves in the equatorial region in the longitudinal axis of the cell, and, 

 after completely coalescing at the poles, constitute the well-known 

 " nuclear spindle." According to the author, the vermiform con- 

 stituents of the nucleus are also enclosed in an exceedingly delicate 

 coat or sac of cellulose, filled with dense protoj)lasm, which draws 

 towards the equator, while the empty ends of the sacs become 

 elongated, finally meeting and coalescing at the poles of the nucleus. 

 Hence the number of nuclear or spindle-threads is normally the same 

 as that of the elements of the nuclear plate. "When the number of 

 threads is larger than that of the elements of the nuclear plate, this 

 is due to the jirotoplasm of some of the smaller elements of the plate 

 being entirely used up in the formation of spindles. This stage is 

 shortly followed by the splitting of the nuclear plate, which usually 

 takes place by the protoplasm of the elements of the plate beginning 

 to move in opposite directions towards the two poles, and thus 

 assuming an elongated form. Reaching the wall of the cell, these 

 strings of protoplasm coalesce in pairs into a V-shaped structure. 

 The nucleoli, which have n-p to this point remained unchanged, now 

 take part in the further changes in the cell. They move towards the 

 middle of the cell, break up into smaller portions, and form in this 

 manner both the protoplasm of the cell, which is compressed from all 

 sides at the plate, and the material for forming the cell-plate. At 

 the line of contact of the plate with the cell-wall of the mother-cell, 

 the young cell-wall first appears in the form of a ring, which quickly 

 grows inwards, and finally developes into a perfectly continuous 

 division-wall. In the daughter-cells thus formed the nuclei divide in 

 just the same way as in the mother-cell. 



Crystalloids in the Cell-nuclei of Pinguicula and Utricularia.t — 

 According to further observations of J. Klein, the crystalloids found 

 in the cell-nucleus of these two plants strongly resemble not only one 

 another, but also those found in Lathrcea squamaria, a point of 

 interest from the fact that Eichler advocates a closer genetic relation- 



* Kosmos, 1881, pp. 158-74 (1 pi.). See Bot. Centralbl., viii (1881) p. 375. 

 t Pringalieim's Jalub. fur wiss. Bot., xiii. (1881) pp. GO-73 (1 pi.). Of. thig 

 Journal, i. (1881) p. 477. 



