STAMINAL HAIRS OF TBADESCANTIA. 435 



glass placed upside down upon the edges of a moist chamber. In 

 this latter way we can retain the hairs in developmental con- 

 dition for a half day or more, although those which lie deeper in 

 the suspended drop will not admit of the use of the higher powers. 

 We must take care, therefore, that the suspended drop is spread 

 out flat. 



The resting nucleus appears finely punctate (Fig. 153, 1, 

 lowest cell) ; but examined with stronger magnification, or in cells 

 which have been brought somewhat under the influence of the 

 surrounding fluid, we see that the minute granules are not isolated, 

 but closely connected into rows, forming fine convoluted threads ; 

 the entire nucleus thus forms a network or framework enclosed 

 in a delicate nuclear membrane. Between the coils of the thread 

 are distinguishable several nucleoli of various sizes. The nucleus 

 is surrounded by cytoplasm, which is connected with the peri- 

 pheral protoplasm by plasmic threads. This cytoplasm contains, 

 besides the scarcely distinguishable microsomata (or microsomes), 

 larger, more strongly refractive grains leucoplasts. The nucleus 

 preparing for division increases in size, and from its fine frame- 

 work forms gradually a coarsely granular thread ; it then begins 

 to elongate, and the coils of its thread arrange themselves 

 obliquely, approximately parallel to one another (Fig. 153, 2). 

 At the same time the cytoplasm begins to collect at the two poles 

 of the nucleus. We can easily observe all these progressive 

 changes in one and the same cell, but this requires a compara- 

 tively long time, and continuous, or only briefly interrupted, 

 observation. The grains in the threads then become indistinct ; 

 this assumes gradually a homogeneous aspect, and lays its coils 

 in a definite fashion which is not in all phases easy to follow. 

 In cells which are dying, the nuclear figures become for a short 

 time clearer. Thus we can conclude from our observations that 

 the coils, in the first place running obliquely, are folded in the 

 equatorial plane of the nucleus, and at the same time are placed 

 parallel to its long axis. Division then takes place into individual 

 nuclear segments, or chromosomes, which form the nuclear 

 plate in the equatorial plane of the nucleus. Not less sharply 

 defined is the stage in which the nuclear segments appear sepa- 

 rated into two bundles of straight rodlets, approximately of equal 

 length, with their ends coming together in the equator (3). If 

 these daughter segments are specially long, they bend, hook- 

 wise, at their polar ends. The nuclear segments are equally 



