Bitter Pit in Aj^ples. 23 



The influence of mechanical injuries. 



Stewart^ noted that in a l)ruise(l fniit, the injured portion con- 

 tained an abundance of starch, but not the uninjured portion. 

 This of course wouhl (inly be the case when the injury was caused at 

 that period of deveK)pment wlien the pulp cells are packed with 

 starch. Bruises on quite young fruits, before the starch grains have 

 l)een deposited, and on adult fruits after they have dissolved, do not 

 show this peculiarity. Varcollier's2 explanation is that in the 

 bruised cells the tannin inhibits diastatic activity. McAlpine (I.e. 

 page 21) states. " The death of the cells, in my opinion, is quite 

 sufficient to account f(ir the persistence of the starch in the bruised 

 cells," being appaicntly vmaware that diastase wiH act as well in a 

 non-living medium as in a living cell. The explanation is merely 

 that the escape of the sap from the bruised dead cells removes the 

 medium into which the protoplasm excretes the sugar as it is 

 formed, so that in tlie protoplasm of the dead cell the percentage of 

 sugar inhibitory to further diastatic action is soon reached. 

 Although diastase is a.faiily stable compound when dry, in the moist 

 cell it soon undergoes post-mortem decomposition, and hence the 

 possibility of a post-mortem diastatic action is limited in time. 



In any case the presence of starch grains in dead pulp cells, and 

 their absence from the living pulp is not an infallible indication of 

 bitter pit, and indeed this symptom only accompanies bitter pit 

 when the defect begins, to develop during the second or " starch " 

 stage of the apple. If bitter pit arises during the early " proteid " 

 stage of the apple or tlie adult "sugar " stage, the dead cells con- 

 tain no more starch than the living ones. (1st paper, pp. 410-415.) 



The relation of Bitter Pit to vascular tissue. 



In tliose cases wliere l)itter pit is due to poisonous substances 

 absorbed through the roots, it would be natuial to expect the dead 

 tissue to l)e more or less closely associated witii the conducting vas- 

 cular bundles. This was actually observed by Wortmann (Landw. 

 Jahrb. xxi. 1892, p. 663), but his generalisation is too sweep- 

 ing. The vascular network in apples is comparatively small 

 meshed, so that any large pit or spot must appear to be associated 

 with a vascular Ixmdle. Small pits, however, particularly when late 

 in development, may I)e found which have no special connection 

 with any one vascular bundle, and larger spots may be sometimes 



1 Stewart, F.C., New York State Station, Bull. 164, 1899. 



2 Varcollier, G , Coinpt. lleiid. Acad. Sei., 141, p. 4li5, 190.=j. 



