636 



DATA OF PROPERTIES OP STARCHES OF PARENT- AND HYBRID-STOCKS. 



starch in 15 minutes; and in about 80 per cent of the 

 grains and 95 per cent of the total starch in 30 minutes. 

 The reaction with mercuric chloride begins in a few 

 grains in 15 seconds. Complete gelatinization occurs in 

 less than 0.5 per cent of the entire number of grains and 

 2 per cent of the total starch in 30 seconds; in about 27 



per cent of the grains and 50 per cent of the total starch 

 in 1 minute ; in about 55 per cent of the grains and 88 

 per cent of the total starch in 3 minutes ; in about 73 per 

 cent of the grains and 90 per cent of the total starch in 

 5 minutes; and in about 88 per cent of the grains and 98 

 per cent of the total starch in 15 minutes. (Chart D378.) 



8. IRIS. 



This genus includes about 175 recognized species, a 

 very large number of garden varieties, and many hy- 

 brids. Apart from the recognized horticultural groups 

 (German, Japanese, Dwarf, and Oncocyclus Irises), 

 these plants are divided into two series which are dis- 

 tinguished by a thick root-stock or creeping rhizome, 

 and by a bulbous root-stock, respectively. Hasselbring 

 includes in the first series the subgenera Apagon, Pardan- 

 thopsis, Evansia, Pseudovansia, Pogoniris and Regelia, 

 and Ocnocyclus; and in the second series, Xiphion, 

 Gynandiris, and Juno. In this research studies were 

 made of the starches of the following species and hybrids : 

 I. iberica Hoffm., J. trojana Kerner, /. cengialti Ambrosi, 

 I. pallida queen of may Hort., I. persica var. purpurea 

 Hort., and I. sincljarensis Boiss. and Haussk. ; and the 

 hybrids /. ismali, I. dorah, I. mrs. alan grey, and /. 

 pursind. The first four of the parents belong to the 

 rhizomatous series, and the last two to the hulbous 

 series. All of the specimens were obtained from Barr and 

 Sons, London. 



30. /. iberica (seed parent), /. trojana (pollen parent), and 



/. ismali (hybrid) , page 636. 



31. /. iberica (seed parent), /. cengialti (pollen parent), and 



/. dorak (hybrid), page 647. 



32. /. cengialti (seed parent), /. pallida queen of may (pollen 



parent), and /. mrs. alan grey (hybrid), page 656. 



33. /. persica var. purpurea (seed parent), /. sindjarensis 



(pollen parent), and /. pursind (hybrid), page 664. 



In the first set, the cross was between members of 

 the subgenera Oncocyclus and Apagon; in the second, 

 between members of the subgenera Oncocyclus and 

 Pogoniris and Regelia; in the third, between members 

 of the subgenus Pogoniris and Regelia; and in the fourth, 

 between members of the subgenus Juno (in the first three 

 between rhizomatous irids; and in the last, between 

 bulbous forms). 



30. Starches of iris iberica, I. trojana, and 



I. ISMALI. 



Iris iberica (Seed Parent). 

 (Plate 18, figs. 103 and 106; Charts D 379 to D 399.) 

 Histologic Properties. 

 In form the grains are usually simple and isolated, 

 though a moderate number of small aggregates of 2 or, 

 rarely, 3 components are noted, and a few compound 

 grains, which are of two types. The first type consists 

 of 2 small grains, each consisting of a hilum and 1 or 2 

 lamella? and surrounded by 8 to 15 common secondary 

 lamella? and attached to the proximal end of a large 

 elongated grain. The second type consists of 2 or 3 small 

 grains, if 3 they are pyramidally arranged, each con- 

 siting of 4 or 5 lamella? and surrounded by 1 or 2 common 

 secondary lamella?. The grains are usually moderately 

 regular in form, and any irregularities which occur are 

 due to the following causes, in order of frequency of 



occurrence: (1) Secondary sets of lamella? whose longi- 

 tudinal axis is at an angle, usually a right angle with that 

 of the primary set; (2) large flattened and rounded pro- 

 tuberances from the sides or from either end; (3) devia- 

 tion of the longitudinal axis with consequent bending 

 of the grain, usually at the distal end, or middle; (4) 

 sharply defined, triangular depressions in the margin at 

 the side, probably representing pressure facets; (5) shal- 

 low, rounded depressions and elevations of the surface, 

 giving a wavy or undulating outline to the margin; (6) 

 rarely, a small, rather narrow, sharply defined notch in 

 the center of the distal margin. The conspicuous forms 

 are elongated elliptical, usually with a flattened distal 

 end, and sometimes with a set of secondary lamella? 

 from one side causing a modification of form, and ovoid, 

 with or without a flattened distal end. The additional- 

 forms are round and nearly round, reniform, pyriform, 

 club-shaped, boot-shaped, napiform, triangular with 

 rounded angles, and short T-shape. The grains are not 

 flattened. 



The hilum is a moderately distinct, round spot and 

 not often fissured. When fissures occur they have the 

 following forms: (1) A small, short, straight, transverse, 

 oblique, or, rarely, longitudinal line; (2) like a flying- 

 bird. Not infrequently 2 refractive fissures are seen 

 extending from either side of the hilum, and appear to 

 be in the inner substance of the grain, and do not come 

 to the surface. The ■hilum is eccentric from 0.25 to 

 0.08, usually 0.15, of the longitudinal axis. 



The lamella; are usually rather coarse and not very 

 distinct, but they may be demonstrated on many of the 

 grains. They are continuous and circular in form near 

 the hilum and in the rest of the grain they usually appear 

 discontinuous and follow in general the form of the out- 

 line of the grain. They often show some irregularities, 

 the chief of which is a small notch or depression corre- 

 sponding to the notch in the distal margin before noted, 

 but this does not always occur in the same grain. There 

 is, frequently, one very coarse, rather refractive lamella? 

 which is placed at either half the distance between the 

 hilum and the distal margin, or very near the distal 

 margin. The number of lamella? counted on the larger 

 grains varies from 8 to 18, usually 12. 



In size the smaller grains vary from 4 by 4/u. to the 

 larger which are 34 by 16/i and 32 by 17^, in length and 

 breadth. The common size is 20 by 14/*,. 



Polariscopic Properties. 



The figure is very distinct and well defined. The lines 

 usually cross at an acute angle which varies considerably 

 in different grains, but sometimes they cross at a right 

 angle. They are often considerably bent, but rarely 

 bisected. 



The degree of polarization varies from low to high 

 (value 50). In a few grains it is low, in very few high, 



