102 TRANSACTIONS OF THE ILLINOIS 



layers of live bark to the alburnum or sap-wood. This will explain why it is not 

 uncommon for trees of slow growth to make their terminal buds on the current year's 

 shoots while blight is yet in the bark. "When this happens, the flow of sap in the 

 bark is arrested, and the wounds made by the blight dry up, leaving the dead patches 

 in the bark which are so often found in the pear. After the poison has passed 

 through the bark to the sap-wood of slow-growing trees, they mostly escape extensive 

 injury from blight, for the same reason, that is, the want of active circulation in the 

 tree to disseminate the vitiated sap . 



The efl:ects of this fungoid growth, inducing pear-tree blight, may be rendered 

 comparatively harmless by a judicious system of root pruning; a rule for which may 

 be found in the society's transactions for 1868, page 36. 



[Note. — Since these instructions in root-pruning were written, we have perfected 

 an implement for cutting the roots of trees by horse-power. Patterns of these cutters 

 are now in the hands of a competent mechanic, who will shortly advertise them for 

 sale.] 



In addition to the instructions as printed in the last year's proceedings, I add th 

 following hints on 



ROOT PRUNING PEAR TREES ON PEAR ROOTS. 



If root pruning the Pear is to be done to induce tardy bearing trees to become 

 fruitful, then the pruning should be done in time, and with sufficient severity, to cause 

 thfe trees to produce their leaves fully grown at least six weeks before frost in autumn. 

 But when the pruning is to be done to ward off the attacks of blight, then the roots 

 must be so much shortened that the trees vnll show terminal buds on leading shoots, 

 at the earhest period that trees are known to show the effects of blight in the sap 

 wood. No rule based on time can be given, since each mile. North or South, would 

 make some variation necessary. Or, to be more explicit: the degree of matui'ity I 

 describe, of course, would be reached earlier South than North. For instance, take 

 Seckel trees makmg moderate growth. These in the latitude of Alton would show 

 terminal buds, at the ends of the latest grooving shoots, about' June 1st. At Villa 

 Eidge and South Pass, the 15th to the 20th of May; while a similar condition of 

 growth, as far north as the north part of Iowa and Galena, could not occur earlier 

 than July 1st. 



For these and similar reasons any rule made as a guide for root pruning must have 

 reference to conditions rather than time. Above I aimed to show that in the early 

 part of the season, the little cell growth, generating pear disease could not in the 

 latitude of Alton, unaided pass through the bark to the sap-wood before about the 

 fii-st of June. These conclusions are based on microscopic examinations, also on 

 observations made on root pruning, extending through a period of more than twenty 

 years. To my mind they establish the fact that in no instance can pear tree blight 

 materially injure a tree on which all the leaf growth is well developed by the time the 

 first branch growth of slow growing Seckel trees is ended; provided a second growth 

 is not made. Excellent examples in support of this view may be lound in the Seckel 

 growing on poor soils. Under such conditions the trees form terminal buds on the 

 strongest of the cm-rent year's shoots at the time we have named. 



It is probable that these slow growing Seckel trees could not blight, in fact do not, 

 until a second flow of sap occurs. On this account, Seckel, and other trees of similar 



