228 Nichols, A morphological study of Jtmiperus communis var. depressa. 



disappear after the reappearance of nucleoli in the resting nuclei. 

 Later, after the homotypic division, small nucleolus-like bodies are 

 frequently found lining both surfaces of the cell plates. These, 

 however, will be referred to presently. 



The body cell and the male cells to which it gives rise also 

 present some interesting problems in connection with the nature 

 of the so-called nucleoli, and it is evident from a study of these 

 cells that the structures are of at least two sorts. The body cell 

 possesses a large vacuolate nucleolus, which is probably homologous 

 with the "plastin nucleolus" described by Coker (1903 b) in Taxo- 

 dium. During the division of the nucleus, however, in contrast 

 to the behavior of the nucleolus of the microspore mother cell, 

 this body appears to shrink in size, although still maintaining its 

 spherical shape, and is recognizable as late as the time when the 

 chromosomes are becoming oriented at the equator (figs. 56, 57). 

 Subsequent to this division prominent nucleoli of the same type 

 reappear in the daughter nuclei. In addition to these structures 

 there are present in the male cells small nucleolus-like bodies, the 

 'pseudonucleoli' of Noren (1907). These are distributed through- 

 out the nucleus, and in view of the absence of any visible chro- 

 matin are regarded by Lawson (1904, 1907) and others as chro- 

 matin gfanules. Outside the nuclei of the male cells, immediately 

 after their formation, and lining the cell plate on both sides there 

 may be found in favorable material granulär or lumpy masses 

 which likewise take the chromatin stains, and which are probably 

 of the same nature as those referred to in the microspore mother 

 cells. These masses are frequently very conspicuous in the young 

 male cells (fig. 58) but usually disappear soon after the laying 

 down of the dividing wall. They are doubtless homologous with 

 the "plastin granules" described by Coker (1903 b) in Taxodium, 

 and it is doubtful whether they ought to be interpreted as nucleoli. 



In the egg nucleus the nucleolus-like structures are still more 

 numerous and are exceedingly difficult to interpret. Frequently 

 the entire chromatic content of the nucleus seems to have resolved 

 itself into nucleoli and pseudonucleoli, yet even after the study of 

 a large number of preparations one is unable to formulate any 

 satisfactory conclusions as to the nature of these structures. That 

 the pseudonucleoli are different from the typical nucleoli, however, 

 seems obvious. Some at least of the former appear to be definitely 

 associated with the reticulum, while in the mature egg nucleus 

 they are the only parts which take the chromatic stains with 

 avidity. It is not improbable that, as Wag er (1904) suggests, the 

 pseudonucleoli "form a part of the nuclear network in which chro- 

 matin or chromatin substance may be stored and possibly to some 

 extent elaborated". 



There is little doubt that many f eatures in these nuclei which 

 appear to be normal, and which have been described as such by 

 various writers, are artefacts, and that the appearances seen in 

 fixed and stained material differ greatly from the structures present 

 in the living nucleus. Chamberlain (1906), after a study of the 



