GENERAL INTRODUCTION 



advisable to add to the compost a little sifted sphagnum, 

 in order to give a spongy, porous consistency which 

 will secure constant and regular " humidification ". 

 Sphagnum here takes the place taken in nature by rock, 

 absorbing and retaining the moisture, which it gradually 

 imparts to the surrounding soil. Of all matter it is par 

 excellence an hygrometric regulator. 



The quickest seeds to germinate are those of Helian- 

 themums, Violaceae, Cruciferae, leguminous plants, Col- 

 umbines, Geraniaceae, and some of the Poppy family. 

 Next come Composite, Caryophyllacese, Potentillas, 

 Onagraceae, Crassulaceae, Labiatae, Scrophulariaceae, 

 Campanulaceae, etc. The slowest belong to the Umbelli- 

 ferse, Gentianaceae, Iridaceae, Primulaceae, and particu- 

 larly to the Berberideae, the Fumariaceae, and a section 

 of the Ranunculaceae (Paeonies, Aconites, Hellebores, 

 Pulsatillas). 



Sir Michael Foster, the celebrated English iris- 

 enthusiast, showed me on April 28, 1905, pots of Iris 

 which he had under observation ; in some of them seed- 

 lings were showing after thirteen years of close attention l . 

 Since then he has recorded in the Gardener s Chronicle 

 the germination of a sowing made fourteen years before. 



One is too ready to count as lost a sowing which does 

 not come up in a few months. At least a year should be 

 allowed before any pan is thrown away, even in the case 

 of families of ready germination, and two years in case 

 of others. In 1890 1 received seed of Jieracleum JWante- 

 gazzianum sent by MM. Levier and Sommier of Florence 

 from the Caucasus. This noble plant would never have 

 been introduced into gardens, 'had I not kept the seeds 

 for three years in the ground, hoping to see them come 

 up; as they did in 1894! Many beautiful species have 



1 H. Correvon's : Les Iris dans les jardins, p. 179. 



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