CHAPTER XXXII 

 ANATOMICAL TECHNIQUE 



As a result of the fact that it has been mainly the soft and repro- 

 ductive parts of plants which in the past have been investigated 

 in connection with the hypothesis of evolution, the methods of 

 examining tissues belonging to these categories have naturally 

 made greater progress than those applicable to the study of harder 

 and vegetative structures. The reawakened interest in fossil 

 plants, which is an important feature of the present phase of the 

 development of morphology, has, however, brought into promi- 

 nence methods for the anatomical investigation of the hard tissues, 

 since in general it is only the harder and consequently more resist- 

 ant parts of extinct plants which furnish a basis for comparison 

 with modern types. This general situation is, moreover, a some- 

 what fortunate one, for it is precisely the enduring woody struc- 

 tures which combine a greater immunity to decay with marked 

 conservatism of organization. Methods of investigating hard 

 tissues in plants must obviously, from the conditions outlined above, 

 include, not only those applicable to relatively unaltered living 

 plants, but also those which may be employed with success in the 

 case of carbonized or petrified vegetable remains. Since the pres- 

 ent volume deals with anatomy alone, it will be possible to confine 

 the description of technique to those processes which are of value 

 in the investigation of the hard parts of plants. 



THE PRESERVATION OF MATERIAL 



In many cases the preserving of material of hard structures 

 in plants does not present a problem of difficulty. For example, 

 petrified or carbonized stems which have survived the destroying 

 influences of often extended time need not be preserved in order 

 to be studied successfully. In such cases the problem of the prepa- 

 ration of the tissues rather than of their preservation is of impor- 

 tance. A similar situation presents itself in the study of woods. 



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