14 MISCELLANEOUS PAPERS. 



there is a ditference in size between the root piece and the 8cion, or 

 where thej^ are more or less imperfectly fitted, as is almost always the 

 case in commercial grafts, the callus formed by the scion and the root 

 piece will not always meet alou^ equal planes. In these cases there 

 will })e a tendency for the callus forming on any surface of either piece 

 which is not in direct contact with an opposite surface (no matter how 

 small this surface may be) to grow out from this surface, either later- 

 ally or down or up, into the air, with nothing to prevent its growing 

 into small lumps, which may reach considerable size. Very frequently 

 the pressure exerted by the growing callus will push the tongue of the 

 graft outward. A thick cushion of callus will then form between the 

 scion and root piece. 



The object of all grafting should be to bring about as rapid a union 

 between the two grafted parts as possible, with the smallest possible 

 period during which an open wound is allowed to remain into which 

 disturbing factors may enter. With this in mind, a num})er of experi- 

 ments were made during the past year, the specific objects of which 

 were to contine the formation of callus as far as possible to the spaces 

 l)etween the root and scion pieces, thereby bringing about a closer and 

 moi-c effective union and reducing the chances for the entrance of 

 possible disturbing factors. 



It is intimated that the formation of the hard and soft types of apple 

 crown-gall may be due either to a proliferation of callous tissue in cases 

 where an uneven union is taking place and where the callus has had a 

 chance to grow out laterally in an unrestricted manner, or to fungi, 

 bacteria, or unfavorable soil or atmospheric conditions.- Whatever the 

 cause, the making of a perfect union in the shortest possible time may 

 serve to prevent the trouble almost wholly if the first explanation given 

 be the cause, and at least largely remove the danger of a possible 

 infection if the second explanation is found to hold good. 



ACCOTJNT OF EXPERIMENTS. 



In order to confine the formation of the callus, a number of grafts 

 were wrapped with various materials during the winter of 1904-5. The 

 wrapping idea is no new one, because cloth and paper were used by 

 nurserymen many years ago in connection with various types of root 

 and top grafting. At the present time cloth and paper are used very 

 little, because the system of thread wrapping will give a larger number 

 of grafts in a given period of time. The materials used in our ex- 

 periments were cloth, thin sheet rubber (dental rubber), and waxed 

 paper. In addition to this, grafts were made with plain thread 

 and waxed thread, and some grafts were wrapped with plam thread 

 and afterwards the whole union was covei-ed with gi-afting wax. 

 One series of grafts was made without any wrapping of cloth or 



100—11. 



