31 



according to my experience, and it may be, in rare cases, none will be 

 seen. The spores are not easy to make out at the first glance, because 

 the broken remains of the banana tissue are often of about the same 

 size as the spores, as are also the fragments of needle-shaped calcium 

 oxalate crystals that may appear in some preparations. After an 

 hour or so in water the spores are more easily seen. Still more readily 

 are they to be seen after germination takes place. Thus, as a rule, 

 after about twenty-four hours in an infusion of banana-peel the spores 

 are readily made out. The most useful and positive results are 

 obtained by this method, so far as relates to identifying the organism 

 in the pustules. 



7 -0 x 3 ' 



Measuremen t s i n 



fe pustule. 



6-0 x 2-5/O 



5 '7 x 3'2fi i Measurements in 



4*0 x 2.5ju 1 micromillimetres 



5-4 x 2-9/t 

 7'6 x 4-0/i 



4 U A T V/yU, | 



5-7 x 2-9 M J 



of six spores from 

 a second pustule. 



Fig. 50. Final stage of banana scab. The skin is entirely dry, grey, and cracked, and the 



pulp is worthless. 



The foregoing are the measurements of two sets of the colourless 

 spores taken from pustules that precede the cracks on scabby bananas. 

 Upon examining the diseased bananas with a magnifying glass, it appears 

 that each crack is probably preceded by a minute pustular outbreak. 

 Upon removing a pustule with the point of a needle, taking care to 

 select a pustule that is recently ruptured or is just about to rupture, 

 one easily secures spores measuring 4' 7 to 7* x 1* to 3*5 micromillimetres, 

 as shown by the above measurements, and averaging 5* to 6* x 3* 

 micromillimetres. These spores are ellipsoidal, or sometimes elongated, 

 colourless, and without any definite and regular internal markings 

 except an uncertain granulation. From the manner of their growth 

 on minute basidia, these appear to be the spores of some Phoma- 

 like form. (See Figs. 51, 52, and 53.) 



An examination of several carefully selected pustules that had not 

 yet been ruptured revealed but few spores of any sort, but those seen 

 were all of the character already described. These were allowed to lie 

 for some time sealed up in an aerated water infusion of banana peel. 

 Only elongated spores were revealed by this germination test. 



In these examinations, care was taken to clean the tops of the 

 pustules before removal from the diseased fruit. 



