4 MASS. EXPERIMENT STATION BULLETIN 330 



The genus Iris is a large one. Bailey's Encyclopedia (Hasselbring in Bailey 

 St. Cyc. Hort. 3:1682. N. Y. 1915) describes 110 species; also a number of 

 botanical varieties. Dykes' outstanding monograph on this genus (Dykes, 

 The Genus Iris, Cambridge, Eng. 1913) lists 139 species with many varieties 

 and hundreds of synonyms. The genus easily divides into several well-marked 

 sections. Garden lovers are familiar, for example, with the German iris, the 

 Siberian iris, and the Japanese iris, and easily recognize the striking differences 

 between these groups. 



Rhizome of German Iris. 



These better-known irises grow from rootstocks or from rhizomes, while the 

 varieties here under discussion grow from bulbs, much like crocus or tulips. 

 All the bulbous irises of special importance to the horticulturist belong to one 

 botanical subgenus called Xiphium, in which group Hasselbring (op. cit.) de- 

 scribes 11 species. Following the classification used by Hasselbring, the botany 

 of the commoner bulbous irises may be summarized as follows: 



Spanish Iris, Iris xiphium, Linn.: leaves narrow and grasslike, about 1 

 foot long; flowers in various colors, blues being prominent, always with a 

 yellow blotch on the falls; bulb small, about 1 inch in diameter. Coming into 

 blossom in June; used in forcing: represented in the American trade by varieties 

 like Cajanus, Louise and Blanche Fleur. 



English Iuis, Iris xiphio ides, Ehrh.: leaves much larger, broader and more 

 abundant; flowers in various colors, blue predominating, large and very showy, 



