16 Botanical Microtechnique 



TABLE 3.1 

 Killing Fluids of the Chrome-acetic and Flemming Type * 

 (The numbers in the columns represent cubic centimeters of the designated reagents) 



* The formulas in Tables 3.1 and 3.2 have been arranged and arbitrarily num- 

 bered, beginning with the weaker solutions. The roman numbers do not correspond 

 with the numbers used in mimeographed editions of this manual. 



contain the bichloride of mercury. After foiu" or five changes of the 

 latter solution, tissties may be stored indefinitely in the last change. 



Chromic acid and acetic acid are the ingredients of an important 

 class of flinds, the chrome-acetic formtdas. These fluids are not used 

 as extensively as some years ago. Table 3.1 gives the proportions of 

 five formtdas. Because of widespread use of the terms weak, medium, 

 and strong for fluids of the type given in Table 3.2, these terms are 

 retained for the series of modifications in the table. The weaker 

 solutions are suitable for succulent or delicate subjects, the strong 

 solution for firm subjects. If this type of fluid is to be used for a 

 critical study, a balanced h)rnuda shoidd be worked out by balancing 

 the shrinking action of chromic acid and the swelling action of acetic 

 acid. 



I'he above lornudas are not very satisfactory for i)idk) or woody 

 subjects because of poor penetrating ability. Use these mixtures for 

 filamentous and thalloici plants, root tips, floral organs, and small 

 sections of leaves or stems. The length ol time recjuired to kill 

 materials varies greatly. Filamentous algae are probably killed in a 

 few minutes. Small })ieces of leaf or root tips require about 12 In. 

 Larger pieces of ti.ssuc shoidd ha\e at least 24 hr. The j)r()gressi\e 

 destruction of (hloroi)h\ll from the cut edges inward is a good gauge 

 of the rate ol action. Piolonged storage in chrome-acetic produces 

 brittleness of the tissues and nuiddy staining effects. Therefore, these 

 fliuds are not suitable iov storage and the tissues nuist be processed 

 after the optinuun interval necessary foi killing. 



