Lily-kin and Rose-kin 133 
When we peel the bark off a spring bough we 
break these forming cells, and the jelly which fills 
them escapes, moistening the wood, and our de- 
structive fingers also. 
During this season of vigorous growth the fibro- 
vascular bundle of a dicotyledon consists, broadly 
speaking, of three parts—the wood, the bast, and 
the generative tissue, full of sap and vitality, 
which lies between them. 
By the end of summer, however, a_ transverse 
section of the bundle in question will show no ac- 
tively-dividing constructive cells. The formation 
of new substances is over for the season, and each 
fibro-vascular bundle now seems to consist of 
but two important elements, wood-vessels and bast- 
tubes. 
But the work of tissue-building in this kind of 
a bundle is not finished. It is merely arrested. 
The constructive life at the core is “« scotched, 
not killed,’’ and after remaining dormant all winter 
it reawakens in spring. Then a zone of construc- 
tive or ‘‘cambium’”’ cells, instinct with creative 
vigor, will come into being between wood and 
bast, and tissue-building will recommence. 
So the fibro-vascular bundles of roses and their 
kin are capable of renewing their growth, year 
