192 TUMOURS OF EUCALYPTS AND ANGOPHORAS, 



pairs, giving rise to composite, shoot-bearing, stem-encircling 

 tumours. The third and succeeding internodes are metre vari- 

 able, but often permit of the addition of a fourth and a fifth 

 pair of fused nodules to the concrescence of the first three pairs. 

 More than five pairs, if developed, are apt to be left isolated, and 

 are only of minor or of no importance. Three to five pairs are 

 the really effective and important ones. 



Fourthly, the hypocotyl is not too long, so that, as the com- 

 posite, stem-encircling tumour increases in size, and grows down- 

 wards, it is able to tamper with as much of the root-system as it 

 encounters, encircling and fusing with the upper portion of the 

 tap-root, and the proximal portions of any lateral roots that come 

 in its way, intercepting more or less of the water they may 

 contain, at the expense of the seedling-stem, and to the ad- 

 vantage of the tumour and its inhabitants. In this stage, they 

 are composite, stem-encircling, shoot-bearing, root-incorporating 

 [but not root emitting] tumours. 



The stem-nodules of seedlings of refractory species, or of re- 

 fractory individuals of any species, may not get beyond the first 

 stage. In such cases, the proliferation slows down, and the 

 axillary stem-nodules come to a standstill. A mild attack has 

 run its course without accomplishing anything of importance, or 

 interfering with the growth-habit of the seedlings. 



Seedlings of susceptible species, from accidental or other 

 causes, may not get beyond the second stage, through the com- 

 posite, encircling tumours failing to incorporate roots. In such 

 cases, the composite tumours may last for some time, but not as 

 long as those which can complete the third stage. 



In the Non Mallee Kucalypts, the last stage may last for some 

 years, until the plants are getting ready to enter on the young 

 sapling stage, but not indefinitely. In the Mallees, however, it 

 may persist throughout life, and the tumours may attain an 

 enormous size. But the distinction between the two groups of 

 Eucalypts does not correspond to inherent differences in their 

 tumours, as such; but to differences in the kind of roots incor- 

 porated in the two cases. In other words, the Non-Mallees have 

 ordinary roots; the Mallees have water-storing roots. 



