266 SUMMARY OF CURRENT RESEARCHES RELATING TO 



lata. They are formed by the original nucleus of the cell becoming 

 constricted, and then breaking up into two or more pieces, without 

 any change of structure being visible in the interior. This takes 

 place only in cells of considerable age, the protoplasm of which is 

 still in circulation and contains chlorophyll and starch. The author 

 prefers for this phenomenon the term "direct division" of the nucleus, 

 rather than " fragmentation," as proposed by Van Beneden. 



Multinucleated Cells.* — Professor E. Strasburger has followed up 

 the observations of Hegelmaier j* and Johow | on the presence of 

 several nuclei in the cells of the embryo of LeguminosaB and in the 

 older cells of Monocotyledons, confirming them in all essential points. 

 He was, however, unable to detect more than one nucleus in the cells 

 of Hemerocallis flava, Canna indica, Sagittaria sagittcefoUa, Sparganium 

 ramosum, Alisma Plantago, Butomus umbcllatus, or Nothoscordon 

 fragrans. Orchis pallens affords a very favourable object for obser- 

 vation. The preparations were either fresh or in alcohol ; in the 

 latter case coloured by borax-carmine. To detect fragmentation of 

 the nucleus, acetic acid with 1 per cent, methyl-green was employed, 

 the fixing and tinging properties of which are very valuable. 



In tlie tissue-cells of Dicotyledons fragmentation of the nucleus 

 appears to be a less common occurrence than in Monocotyledons. It 

 was observed in the pith of Tropceolum majus and of species of 

 Nicotiana, but only in very old cells shortly before the disorgani- 

 zation of the nucleus. As has been already observed also by Treub 

 and Hegelmaier, the phenomenon is very easily observed in the 

 suspensory cells of the embryo of Viciefe, and of the section capnoides 

 of Corydalis. 



According to Strasburger, the two phenomena of the division and 

 fragmentation of the nucleus are not identical. Division of the 

 nucleus takes place in cells with active vitality, and under the in- 

 fluence of the surrounding protoplasm ; fragmentation, on the 

 contrary, is a process belonging to the nucleus only, which does 

 not set up until the influence upon it of the surrounding proto- 

 plasm has ceased. It obviously leads, in many cases, to a rapid 

 disorganization of the nucleus ; in other cases, however, this does 

 not follow rapidly, and the cell then remains for a long time in a 

 multinucleated condition. A very favourable illustration of frag- 

 mentation is presented by the internodal cells of Cliara. "When 

 fragmentation of the nucleus has taken place, the cell-protoplasm 

 would appear to be no longer capable of division. Normal nucleus- 

 division in active cells occurs in many Algae, Fungi, and Protophyta. 



All cases of lobed and partially constricted nucleus are not, how- 

 ever, due to fragmentation ; they sometimes result from a process 

 of coalescence of nuclei. This occurs not unfrequently in the for- 

 mation of endosperm, as in Corydalis cava, and in Ephedra at the 

 period of maturity of the corpuscula and commencement of the deve- 

 lopment of the embryo. 



* Bot. Ztg., xxxviii. (1880) pp. 845-54 (pi. xii. figs. 1-22). 



t See this Journal, iii. (1880) p. 979. % Ante, p. 265. 



