92 abstracts: forestry 



The organism loses virulence easily both inside the tumors and in cul- 

 ture-media, and finally if the plants are not destroyed by it they seem to 

 acquire a partial or complete immunity. 



The Bulletin involves team work done by four people in the Depart- 

 ' ment of Agriculture, covering a period of seven years and the total num- 

 ber of experiments involved amounts to thousands. 



Circular No. 85 gives in outline the results of further studies on resem- 

 blances of crown-gall of plants to malignant animal tumors. Since 

 Bulletin 213 was published it has been found that the primary tumors 

 are connected to the secondary ones by means of a deep-seated strand 

 of tumor tissue. This strand occurs in the inner wood or at the junc- 

 tion of wood and pith, and wedges apart the normal tissues of stem 

 and leaves quite after the manner of a foreign body, giving rise in vari- 

 ous places to the secondary tumors. 



When the primary tumor occurs on a stem, secondary tumors fre- 

 quently appear in the course of a few weeks or months at a considerable 

 distance on leaves, and in this case the same thing happens as in meta- 

 stasis of malignant animal tumors, viz., the structure of the secondary 

 tumor is that of the primary tumor and not that of the tissue in which 

 it is lodged. In other words, the leaf tumors of this derivation have 

 the anatomy of the stem. 



The bacteria occur within the multiplying tumor cells and it is through 

 their action on the nucleus that these cells are compelled to divide and 

 take on the abnormal rapidly multiplying tumor growth. The bac- 

 teria have been found (sparingly) in the secondary tumors and in the 

 strands connecting these to the primary tumor. There is no reasonable 

 doubt, therefore, that we have in this disease a type of cell multiplica- 

 tion closely parallel to that which occurs in malignant animal tumors. 



Full details will be given in another bulletin as soon as the photomi- 

 crographic illustrations can be prepared. E. F. S. 



FORESTRY. — -Windbreaks: their influence and value. Carlos G. 

 Bates. Forest Service Bulletin No. 86. Pp. 106, with plates 

 and diagrams. 1911. 



Windbreaks may be used profitably in the middle west, the northern 

 prairies, the lake states, the eastern states north of the forty-ninth 

 parallel, the southwestern states, and in the fruit growing regions of the 

 Pacific coast. 



The distance at which the effect of a windbreak may be felt averages 



