5i6 BOTANICAL GAZETTE [june 



grassland plants derived from buried seeds are so consistent and so regularly- 

 associated with the history of the land that one is irresistibly forced to the 

 conclusion that when arable land is grassed over, a certain number of the seeds 

 are able to retain their vitality for very many years. Many of the seeds die 

 within a comparatively short time after burial, and as time goes on the number 

 of living seeds gradually becomes less, although the evidence goes to show thaf 

 some seeds will survive burial for at least 58 years. Usually most of the older 

 arable seeds survive in the lower depths of soil where the conditions are less 

 variable, whereas the shorter the time that land has been under grass the greater , 

 the proportion of arable seeds that are found near the surface. While the stock 

 of arable seeds is diminishing with the lapse of time, the supply of grassland seeds 

 is being augmented by fresh seeds that are ripened by the surface vegetation 

 and are gradually carried down into the soil. Naturally enough, the greater 

 number of these seeds are found in the upper inches of soil, comparatively few 

 penetrating below the eighth inch." 



Miss Brenchley fails to note the much earlier and extensive work (1893- 

 94) of Peter, which is very similar to hers in method and conclusion. She 

 also fails to mention the well controlled work of Beal and of Duvel on the 

 longevity of buried seeds, which likewise justifies her conclusions.* — Wm. 

 Crocker. 



Wound callus and bacterial tumor. — Polar difference in wound callus 

 formation has often been observed in stems, and less frequently in root 

 structure. Magnus' finds that segments of the root of a half long carrot 

 with which he worked produced a wound callus on the morphologically apical 

 face, but not on the basal face. This occurred whether the apical face was 

 oriented upward or downward in the moist chamber. The callus starts at the 

 cambium ring and spreads centripetally. When the apical face is infected with 

 Bacterium tumejaciens the callus development is much greater. When the 

 basal face is infected there is a considerable development of tumors on that 

 face, and this acts in a correlative way to inhibit the normal tumor develop- 

 ment in the apical face. Magnus also worked with a long fodder carrot. 

 While infection in this form increased the callus development on the apical 

 face of the segments tenfold, it induced very little tumor development on the 

 basal face, and accordingly showed little correlative effect in inhibiting the 

 normal development on the apical face. 



Magnus offers evidence for the view that the tumor inducing organism in 

 plants is not identical with that in man. He also suggests that certain con- 

 clusions of Blumenthal and Hirschfield on the effect of Diplococcus in 



' See Crocker, Wm., Mechanics of dormancy in seeds. Amer. Jour. Bot. 3:99- 

 120. 1916. 



■'Magnus, Werner, Wund-callus und Bakterien-Tumore. Ber. Deutsch. Bot. 

 Gesells. 36:20-29. 1918. 



