36 THE BOOK OF THE IRIS 



Differences are here extreme and no greater could 

 perhaps be met with, but nevertheless some success has 

 been claimed, even in Holland, with soil as above indi- 

 cated. Mr Hoog in his article remarks that he would 

 have added dolomitic limestone finely ground to his soil, 

 had it been possible to get it, since it contains a high 

 percentage of both lime and magnesia. Failing this, he 

 tried a sample of marl, for lime, selected because of its 

 only very feeble phosphoric acid, and to provide the 

 magnesia he used Grecian Magnesite, which was easily 

 obtainable. For experimenting with, ten beds were 

 made, each eight yards long by one wide. The 

 Oncocycli were planted in December 1899, anc ^ at ^ e 

 same time the first bed had a dose of 1 1 Ibs. of marl with 

 4! Ibs. of magnesite, strewn between and over the Iris 

 rhizomes. This quantity was increased in the remain- 

 ing beds, so that, to the last, a maximum dose of nearly 

 66 Ibs. of marl was given, with 31 J Ibs. of magnesite. 



" It soon became evident that there was a marked 

 difference between the formation of new roots emitted 

 by the rhizomes planted in the prepared beds and 

 those planted in our ordinary soil. In the latter case 

 roots were forming slowly and sparingly, whereas 

 on the marl and magnesite many more new roots 

 were developing which also grew much faster. The 

 difference in leaf growth in the spring also became most 

 strongly marked, and I never saw finer and healthier 

 specimens of Oncocycli than my treated plants became in 

 the course of the spring and summer of 1901." 



The experiments also showed that in my Haarlem soil 

 (moist, well enriched sand) there was no difference in the 

 growth by plants in beds to which the maximum dose 

 (66 Ibs. of marl and 31 \ Ibs. of magnesite) had been 

 added, from those on the bed with about 44 Ibs. of marl 

 and 19! Ibs. of magnesite; but there was a marked 

 difference in the luxuriant growth of the Irises on the 



