324 



JOURNAL OF THE EOYAL HORTICULTURAL SOCIETY. 



ON SOME EXPERIMENTS IN THE CULTIVATION OF 



ONCOCYCLUS IRISES. 



By John Hoog (C. G. Van Tubergen, jun., Haarlem). 



For the past twelve years or so I have paid a special attention to the 

 growing of the Oncocyclns class of Irises, which with me, as with so 

 many growers, do well the first year after importation, but which on 

 subsequent cultivation generally diminish gradually in health and 

 strength, the end usually being an almost complete failure. Many and 

 varied have been my experiments with these Irises. I planted the 

 rhizomes early and late, on light and on heavy soils, in dry and in moist 

 situations, and although every year I felt that I learned somewhat, still 

 it was clear to me that some, for the time, insurmountable barrier yet 

 lay between my efforts and success. At last, in 189H, I hit upon the 

 idea of having some soil sent to me from the very spots where the 

 Oncocyclus Irises grow wild. As I then happened to have a collector in 

 the mountainous region stretching eastwards of the Armenian town 

 of Van, whence I received a plentiful supply of various Oncocyclus 

 Irises (the new /. urmiensis, I. paradoxa var. Choschab (fig. 173), and 

 I. lujjinaxsbv. SchadacJi among them), it was easy enough for me to have 

 some of the original soil sent, together with a consignment of various 

 bulbs and roots, from that district. This soil I sent to a competent 

 chemist to be carefully analysed, and I did the same with my own 

 garden soil. The two different analyses I have pleasure in communi- 

 cating hereunder, and they may be said to represent a story ^\dthout 

 words, yet of the utmost importance ; — 



Analysis of soil in which Oncocyclus 



Analysis of Dutch Bulb 



Irises grow 



wild. 



garden soil. 





Grammes per kilo soil 



(Irammes per kilo soil 



Sulphuric acid (SO3) . 



. 0-087 



0-0812 



Chlorine (CI) 



. 0-034 



0021 



Phosphoric acid (P.^O^) 



. 0044 



0-6o6 



Lime (CaO) . ' . 



. loo-SO 



1-840 



Magnesia (MgO) . 



. 49-56 



0-516 



Oxide of iron (Fe.,0.j) . 



. 30-78 



5-240 



KaU (K,0) . ' . 



. 0-198 



0-206 



Natron (Na.,0) 



. O-OoO 



0-054 



Alum (AL.O^) 



. 7-581 



traces 



The great difference in the quantity of such an important factor in 

 plant-life as lime is, which was found in the Dutch soil and in that from 

 Armenia, made it clear to even the most uninitiated observer that no 

 plant could be expected to feel happy in a ground containing not even 

 two grammes of lime per kilo of soil, whereas this same plant naturally 

 grows wild on sites with 155 grammes per kilo. This difference is 

 immense, and so it is with the magnesia. Naturally the idea suggested 

 itself that a great step in the right direction would be made if one 



