16 



Thus it appears that the granulation of the spores is coarser when 

 young than when more mature. In the case of the spores of the guava 

 Gloeosporium cultivated on the apple,, the earlier spores from the first 

 pustules that appeared were removed and examined before the pustules 

 had burst, yet at a time when the spores were readily obtainable in 

 large numbers. Several days later, when more pustules had appeared, 

 spores were taken from a pustule that had begun to emit the spores 

 in " tendrils." Comparison with the spores taken at an earlier date 

 showed that these later spores were more regular in form and more 

 finely granular, and had a more distinct vacuole than those of an 

 earlier date. 



Similarly in another case when spores were removed from a young 

 pustule of the Gloeosporium of the banana inoculated on to the apple, 



' Fig. 40. Spores of the Gloeo- 

 sporium produced on apple 

 by inoculating- it with Gloeo- 

 "Fig. 39. Spores of Gloeosporium grown on .$ sporiuin !spores found grow- 



the apple from an inoculation from banana ^vr^, l :: ing naturally on the guava. 



Gloeosporium. These spores are some- 

 what unripe, i.e., were taken from pustules 

 of slow growth and not yet burst. * 400 



the spores were found to be very coarsely granular and without a 

 vacuole, the normal form of these spores on pomaceous fruits being 

 finely granular. (See Fig. 39.) 



It has been necessary to bear these facts constantly in mind while 

 carrying on the experiments recorded in these pages. If, for 

 instance, the earlier spores resulting from an inoculation on to a new 

 fruit were compared with a mature spore from the original, the results of 

 the comparison would be of less value than if 'the spores were mature 

 on both occasions. No rule can be laid down for guidance in such 

 comparisons because, on account of the varying composition of different 

 fruits, the appearances of the ripe pustules vary considerably. It 

 would seem that a pustule that is actively " spouting" spores might 

 be safely taken as beyond question mature, and in the comparisons 

 here made, as far as possible, spores for comparison were derived 

 from "spouting" pustules. 



Unfortunately, however, the varying nature of the epidermis of the 

 various fruits is a factor difficult to allow for in making comparisons. 

 To illustrate the nature of the comparisons made, and the obstacles 

 encountered, and the results that may be obtained if the difficulties are 

 not too great, let us return to the cultures of the Gloeosporium of the 

 guava. We find that the spores of this form, as they occur on the 

 guava, are rather more elongated than usual, coarsely granular, 

 provided with a rather indistinct vacuole, and characterised by a 

 peculiar colouration. When viewed in optical section the spore walls 

 appear to be colourless and the granules nearly so, but with a 

 delicate shade of green. If the lens be next raised a trifle, the spore 

 wall takes on a pinkish tint, the change reminding one of the change 

 of tint noticed in those substances, such as eosin, that in one light 



