84 PRACTICAL BOTANY 



sharply defined from one another at a point immediately below 

 the apex ; but the various tissue-systems appear to originate from 

 a common meristem. In some cases, however (especially water 

 plants), the definition is more marked. As an instance may be 

 cited the apex of Hippuris (see below, p. 111). 



Cell-division. 



In the preceding pages reference has repeatedly been made to 

 cell-division, and to meristematic tissues, i.e. those in which the 

 cells are actively multiplying by division : observations should 

 now be made of the various stages of the process, and these may 

 be carried out either (1) directly upon living cells, or (2) by 

 examination of tissues which have had their cell-contents 

 suddenly fixed and hardened while the process of division of the 

 cells was in progress. 



I. Direct observations of cell-division may be conveniently 

 made by examining the hairs on the stamens of Trade scantia. On 

 a warm day take a bud which has not yet attained half the size 

 which it would have immediately before opening : cut away its 

 base transversely so as to remove the receptacle, and press 

 gently between the finger and thumb : the stamens and pistil 

 will be squeezed out : the former are to be placed on a slide 

 in a drop of 2 per cent, sugar solution, remove the anthers and 

 cover the filaments with a cover-glass. Examine under a low 

 power and note the somewhat beaded hairs attached to the 

 filaments of the cells : at, or near to the ends of the hairs, some 

 will be found to contain a single well-defined nucleus, of 

 roundish form ; others of the terminal cells may show a more 

 elongated form, and the nucleus be also elongated and its outline 

 ill defined : the latter are in course of division, and the details of 

 the process may be followed in an individual cell, by watching it 

 under a high power. The hairs thus mounted in sugar solution 

 will continue their normal life for some time, but for prolonged 

 observation it will be better to mount another preparation in a 

 hanging drop of 2 per cent, sugar solution, and keep it in a moist 

 chamber (see Appendix A). The following characters are to be 

 noted in a resting cell as seen under the high power : 



