688 STAKCHES OF IRIDACE^. 



STARCHES OF IRIDACE^. 



Class, Monocotyledones. Order, Liliales. Family, IridaceE. Genera represented: Iris, 

 Morea, Homeria, Tigridia, Gladiolus, Watsonia, Tritonia, Freesia, Antholyza, Crocus, 

 Romulea, Cypella, Marica, Gelasine, Sparaxis, Ixia, Babiana. 



The Iridacece or Iridece includes 57 genera and about 700 species, natives chiefly of the Mediter- 

 ranean region and South Africa, and to some extent of Australia, Asia, and America. Representa- 

 tives of 17 genera were studied. 



GENUS IRIS. 



There are over 170 species of Iris, over 100 of which and a very large number of garden 

 varieties are in cultivation. They are natives of the north temperate region of Asia, Europe, and 

 North America; and also of Africa north of the Atlas Mountains, the southern representatives in 

 the latter country being classified as Mora;as. Four recognized horticultural groups include: (1) 

 the German irises, the best known of which are /. germanica, the fleur-de-Us or blue flag; and I. 

 florentina, the source of the orris-root of commerce; (2) the Japanese irises, including a large 

 number of garden forms which are referable to /. Icevigata; (3) the dwarf irises, referable to /. 

 pumila, I. verna, and /. cristata; (4) the Oncocyclus irises, in certain respects distinctly differen- 

 tiated from the other groups. These plants are also classified into two series, which are distinguished, 

 respectively, by a short, thick root-stock or creeping rhizome, or by a bulbous root-stock. Has- 

 selbring includes in the first series the subgenera Apogon, Pardanthopsis, Evansia, Pseudovansia, 

 Pogoniris, Regelia, and Oncocyclus; and in the second series, Xiphion, Gynandiris, and Juno. 

 Starches from thirteen sources were studied, which are distributed among the two series and the 

 ten subgenera as follows: Series 1, subgenera Pogoniris and Regelia: Iris florentina Linn., I. pal- 

 lida var. speciosa Hort., and I. pumila var. cyanea Hort.; subgenus Oncocylus: I. hismarckiana 

 Hort. and /. iberica Hoff. Series 2, subgenus Xiphion: I. xiphium var. grand tresorier Hort., 

 7. xiphium var. wilhelmine Hort., I. xiphium var. lusitanica Hort., /. tingitana Boiss. and Rent 

 (7. reticulata M. Biev.), and 7. histrio Reichb. f. {Xiphium histrio Hook, f.); subgenus Juno: I. 

 alata Poir. (7. scorpoides Desf.) and 7. caucasica Hoffm. 



STARCH OF IRIS FLORENTINA. (Plate 63, figs. 373 and 374. Chart 255.) 



Histological Characteristics. -In form the grains are usually simple. There are a few compound 

 grains, small aggregates, grains with pressure facets, and clumps consisting of very minute grains. 

 The surface is often irregular. The irregularity of the simple grain is generally due to rounded 

 protuberances, more frequently located near the hilum, or to a secondary deposit of starch in such 

 a way that the longituchnal axis of one or more sets of lamellae is placed at varying angles, commonly 

 at right angles, to the same axis of the primary grain; and also by a cup-shaped depression at the 

 distal end of the primary set of lamellse, as well as frequently of the secondary set. The conspic- 

 uous forms of the simple grain are the elongated ovoid with a squared, hollowed distal end, and 

 the oval and finger-shaped with a similar distal end; also a cone-shaped grain with rounded apex 

 is occasionally present; and as results of secondary deposits upon the primary grain various forms, 

 such as boot-shaped, bow-shaped, T-shaped, L-shaped, and laterally curved club-shaped are found. 

 The conspicuous forms of both the compound and aggregate grains are heart-shaped with blunt 

 apex, and knob-shaped. These grains are formed by the union of oval or rounded grains, the 

 proximal ends being either closely fitted or flaring from each other. There may or may not be a 

 secondary deposit of lamellae common to both grains. Both compound and aggregate grains are 

 also found composed of one small grain attached to the distal end of a large grain, and other forms 

 of doublets and occasionally triplets arranged triangularly or linearly. The grains are not flattened. 



The hilum appears as a distinct, clear, round spot, centric in the small, round forms and eccen- 

 tric one-third to one-sixth, usually one-fourth, of the longitudinal axis in the elongated larger forms. 

 Either a cavity or a cleft may appear at the hilum. These clefts are usually transverse, cross-shaped, 

 or stellate. One delicate, short, longitudinal fissure generally runs from each side of the hilum. 



The lamellce are rather coarse, but generally not very distinct; often they can not be observed 

 near the hilum, but sometimes they appear here as complete rings. Beyond this region they assume 



