PREPARATION OF DRIED SPECIMENS FOR EXAMINATION 89 



nation, but the examination of their structure and contents constitutes 

 perhaps the most difficult part of floral dissection. It is very desirable 

 that the stigmas be subjected to examination with the compound 

 microscope, as the character of its surface and the form and distribution 

 of the stigmatic surface proper upon the style and upon the body, 

 which may at first sight be regarded as the stigma, is frequently a matter 

 of the utmost importance. The dissecting knife must now be used for 

 dividing the ovary into a number of transverse sections, which must 

 then be separately viewed by transmitted light. This examination will 

 determine the number of cells and their completion by the continuation 

 of the septa from top to bottom. It will also in most cases be sufficient 

 to enable us to determine the number of ovules and the position and 

 character of the placentae. All these points should, however, be veri- 

 fied by the subsequent examination of vertical or longitudinal sections. 

 Finally the ovules must be removed and their form and structure 

 determined by the aid of a compound microscope. 



It may be pointed out in conclusion that the examination of a single 

 flower is not always sufficient to determine the structural characters. 

 Dimorphism or dichogamy, unrecognized by the student, may lead to 

 the most false conclusions. 



The student should also be cautioned against the temptation to 

 examine the partially or wholly matured fruit with the idea that he 

 can thus more easily determine the characters of the gynaecium. As 

 will be shown later, great changes frequently occur in the structure 

 of the pistil during fructification. 



Preparation of Dried Specimens for Examination. — The order of exam- 

 ination is the same whether a fresh or a dried flower be under considera- 

 tion. In the case of the latter, however, it is necessary that it be first 

 thoroughly softened by immersion in water. For this purpose it may 

 be left in warm water all night or for a longer period, or as is usually 

 more convenient, it may be boiled for from one to five minutes, accord- 

 ing to its texture, in a spoon or porcelain dish held in the flame of an 

 alcohol lamp. Considerable experience is required to know just how 

 long to subject it to the action of the hot water. If too quickly removed, 

 the tissues will be found stiff and resistant, while if it be boiled too 

 long, they will become so thoroughly limp as to lose all trace of their 

 natural position. If the process is perfectly performed, the flower may 

 be thrown upon a blotter and after the excess of moisture has been thus 

 removed, will be found very much in the original growing condition 

 and yielding easily to manipulation. 



