1898] NOTES AND COMMENTS 303 



accuracy, with the methods of other countries working similar 

 territory. One reason why it is difficult to use photography to the 

 same proportionate extent, as is done, say, in the printing offices at 

 Southampton, is that the American maps are all printed in a con- 

 siderable number of colours. Of course, even in this case, it might 

 be urged that the black printing could be done from photo-gravure 

 plates, and the colour plates made on transfers therefrom, but the 

 American surveyors seem to decidedly prefer to have their maps 

 finished up by the workers actually in the field. The result of this 

 is that, although the field worker's map is perfectly accurate for 

 engraving by hand, it is not sufficiently clean and sharp in its lines 

 for direct photo-engraving ; hence, if photographic reproductions were 

 used, it would be necessary to make a clean copy by hand in the 

 establishment, and it is considered more accurate and more 

 economical to make a transfer from the field map direct to the 

 copper-plate and to engrave it by hand. The exceedingly low price 

 at which the maps of the Survey are sold, shows that their cost of 

 production must be reasonable, since they are supposed to be sold at 

 cost price, and certainly their cost to the public compares very 

 favourably with the price of the maps produced by the British 

 Surveys." 



EusT ON Cereals 



Professor J. Eriksson has published in the Botanical Gazette, vol. 

 XXV., Jan. 1898, a short account of the results he has obtained 

 from his researches on the rust of cereals at the experiment station 

 of the Eoyal Swedish College of Agriculture. 



He subdivides the three species of rust, Fuccinia graminis 

 Pers., P. ruhigo-vera D.C., and F. coronata Corda into ten distinct 

 species, and he finds further that forms of these have become re- 

 stricted to particular hosts ; the danger of infection spreading from 

 one diseased grass to that of another genus or species is tlnis very 

 much lessened. Another point of extreme interest is the difficulty 

 he found in inducing certain teleutospores to germinate until, by 

 laying them on ice, he imitated natural conditions of winter tem- 

 perature. This explains the difficulty experienced in germinating 

 the spores obtained from straw used as manure, and it gives the 

 agriculturist greater confidence in using rusted straw. 



• After many experiments Professor Eriksson has come to the 

 conclusion that though rust increases by infection it is largely 

 propagated by inheritance. He supposes that " the fungus lives for 

 a long time a latent symbiotic life as a mycoplasma in the cells of 

 the embryo and of the resulting plant, and that only a short time 

 before the eruption of the pustules, when outer conditions are favour- 

 able, it develops into a visible state assuming the form of a mycelium." 



