M a ri| u etl c. Manifeetations of polarity in plant cells which usw. 29S 



mother-cell. Kays which extend almost to the cell periphery center 

 upon this mass which elongates and finally constricts in the middle. 

 The daughter masses separate from each other iintil they lie almost 

 at the foci of the ellipsoidal mother cell. Arrived here they once 

 more elongate, this time in two planes at right angles to each 

 other and to the plane of the first elongation. ConstrictioB in the 

 middle again follows this elongation so that the mother cell now 

 contains fonr such masses arranged in the form of a tetrahedron 

 abont the nuclens and snrroiinded on all sides by protoplasmic rays. 

 Now the nucleus begins to divide. Although Fitting's material 

 diel not snft'ice for a detailed study of mitosis, he made the impor- 

 tant Observation that the poles of the first spindle lie respectively 

 in the middle between two of the starch masses, apparently between 

 two sister masses. The spindles of the second division are perpen- 

 dicular to each other, the poles lie close beside one each of the 

 fonr starch masses but they never end directly in a starch mass, 

 always lying a little to one side of them and entirely free in the 

 cytoplasm. Fitting also briefly inclicates the theoretical interest 

 of the described observations without going further, however, than 

 to point out that in certain cases even amongst the Archegoniates 

 cell division may be initiated by a division of the cytoplasm and 

 the included reserve materials; and that the conditons as they are 

 found in the macrospore-mother-cells of Isoetes deserve to be 

 taken into aeconnt by the students of cell-mechanics. Fitting 

 worked with preference on living material, which has its nndeniable 

 advantage, at the same time it is to be hoped that microtome 

 sections prepared after successful fixation (which here meets with 

 considerable difficiilties) will show an abundance of additional 

 important details. 



The behavior of the chloroplasts in Coleochaete is also of 

 interest. According to Oltmanns 1 ) there is a Single chloroplast 

 lying at the basal end of the unfertilized oosphere. After the 

 entrance of the male cell (which does not contain a chloroplast) 

 the chloroplast divides, the halves taking position at opposite sides 

 of the fusing sex nuclei. The division of the chloroplast is twice 

 repeated so that finally there are eight of them in the oospore, 

 Now nnclear division begins; nsnally there are three snecessive 

 divisions of the nuclens resulting in the formation of eight nuclei. 

 Cell division follows, producing eight carpospores, each of which 

 contains one nucleus and one chloroplast. Aside from the fact 

 that cell division oecurs so that finally each carpospore contains 

 one chloroplast there are no Statements as to the relations between 

 the chloroplasts and the karyokinetic figures. In his figure 7 

 Oltmanns shows two cells, apparently belonging to an antheridial 

 branch, whose nuclei are in the eeuiatorial plate stage. A chloro- 

 plast lies opposite each spineile pole; however. from this fact 

 alone it is not possible to conclude much regarding the relations 



] ) Oltmanns, Fr.: Die Entwickelnno' der Sexualorgane bei Coleochaete 

 pulvinata. (Flora IM. 85. 1898. p. 1.) 



