42 TOBACCO BREEDING. 



ner ° which describes this apparatus and method of Laboratory tests 

 of the burn of tobacco in detail. By smoking several cigars at the 

 same time by the use of this device it is possible to make very close 

 and accurate observations on the rate and evenness of burn, color of 

 ash, and other characteristics of the tobacco from different plants. 



Cigars are prepared for this test from all the samples to be tested 

 from the different plants and are alloAved to dry out under natural 

 but uniform conditions. The method employed by the writers in 

 determining the comparative combustibility of the leaves from each 

 seed plant is as follows : 



One cigar is made wholly from the leaves of each plant, using the 

 top leaves for filler, those next to the top for binder, and one side of a 

 middle leaf for the wrapper. The other half of the wrapper leaf 

 is reserved for a supplementary test, which will be described later. 

 The object in making the entire cigar from the same plant, whether 

 it is a filler or a wrapper type, is to eliminate the possible influence 

 of any other tobacco upon that which is being tested. After the 

 cigars have dried sufficiently, they are placed in the apparatus for 

 smoking and all drafts excluded from the room to secure absolute 

 uniformity of conditions. A\Tiile the cigars are burning they are 

 scored on the several points which go to make up a good or poor burn. 

 The differences in character of burn of tobacco from the different 

 plants when smoked under these uniform conditions is very surpriz- 

 ing, and shows clearly the variability of the quality of burn in 

 tobacco produced by different plants grown under uniform conditions. 



The rate of burn is carefully determined, and the degree of uni- 

 formity or evenness noted. Some cigars will burn down on one side 

 and go entirely out on the other, while otliers burn completely and 

 evenly. Some will burn much more rapidly than others and with 

 greater evenness. In many cases the wrapper puckers or swells just 

 ahead of the fire, and often a shiny, metallic, black ring will appear 

 just back of the burning tobacco. Sometimes both of these phe- 

 nomena are present, and in this case the black ring, which indicates 

 what is known as a metallic burn, appears between the fire on the 

 cigar and the ring caused by the puckering or swelling of the leaf. 

 These rings indicate a poor burn and are invariably associated with 

 poor-burning tobacco and very frequently with an undesirable or 



bitter taste. 



The comparative degree of coaling, i. e., a swelling of the wrapper 

 at the burning point leaving a black ash, can be readily determined 

 and noted in these tests. The character of the ash is also considered 

 very important, and in case it flakes badly or is of a very dark, dull 



o Bulletin No. 100, Part IV, Bureau of Plant Industry, U. S. Department of 

 Agriculture. 

 96 



