IRIS. 



639 



moderate number of grains the proximal portion becomes 

 gelatinized first and then the distal starch. In the two 

 methods of gelatinization just described, the enlargement 

 of the grain is greatest at the distal and the proximal 

 ends, respectively. The gelatinized grains are large, have 

 thin capsules, and -are somewhat distorted, but retain 

 some resemblance to the form of the untreated grain. 



The reaction with potassium sulphocyanate begins 

 immediately. Complete gelatinization occurs in about 

 38 per cent of the entire number of grains and 84 per 

 cent of the total starch in 2 minutes; in about 5G per 

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

 5 minutes; in about 76 per cent of the grains and 97 per 

 cent of the total starch in 15 minutes. (Chart D 387.) 



The reaction with potassium sulphide begins in 30 

 seconds. Complete gelatinization occurs in less than 0.5 

 per cent of the entire number of grains and 4 per cent 

 of the total starch in 5 minutes; in about 1 per cent of 

 the grains and 5 per cent of the total starch in 15 min- 

 utes; in about 1 per cent of the grains and 6 per cent 

 of the total starch in 30 minutes ; in about 2 per cent of 

 the grains and 7 per cent of the total starch in 45 min- 

 utes; in about the same of the grains and 8 per cent of 

 the total starch in 60 minutes. (Chart D 388.) 



The reaction with sodium hydroxide begins imme- 

 diately. Complete gelatinization occurs in about 39 per 

 cent of the entire number of grains and 59 per cent of the 

 total starch in 2 minutes; in about 60 per cent of the 

 grains and 80 per cent of the total starch in 5 minutes ; 

 in about 70 per cent of the grains and 88 per cent of the 

 total starch in 15 minutes; in about 83 per cent of the 

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

 in about 88 per cent of the grains and 97 per cent of the 

 total starch in 45 minutes ; little if any further advance- 

 in 60 minutes. (Chart D 389.) 



The hilum is very distinct and 2 refractive fissures, 

 which are either already present in the untreated grain 

 or soon form after the reagent is added, become larger 

 and more extensive and branch out considerably as 

 they near the distal margin. The lamella? are moderately 

 distinct and remain so, at the proximal end, throughout 

 the greater part of the reaction. Gelatinization begins 

 at the hilum which increases in size somewhat, as do also 

 the 2 fissures already described, which by their many 

 fine branches divide the grain at the distal end into fine 

 granules. The portion of the grain between these fis- 

 sures, the hilum, and the distal end, is invaded by many 

 irregular, more or less longitudinal fissures, and as the 

 hilum continues to enlarge and the grain to swell these 

 fissures widen and divide this part of the starch into 

 rather thin pyramids, from which spicules separate off, 

 partially or completely, and are gelatinized. In many 

 grains there are also wide cracks and longitudinal fis- 

 sures which invade the distal portion of the grain from 

 the margin, and when this occurs, the distal end and the 

 material at the hilum both begin to gelatinize at nearly 

 the same time. The more resistant part of the grain is 

 at the proximal end and sides nearby, and this material 

 forms a faintly lamellated, rather refractive band at the 

 margin which later becomes coarsely striated, and so 

 divided into granules. This band becomes progressively 

 thinner and more nearly transparent as the grain en- 

 larges, until finally only the thin capsule remains. 



The gelatinized grains are swollen, and have rather 

 thick capsules. They are not much distorted except at 

 the distal ends, and retain some resemblance to the form 

 of the untreated grain. 



The reaction with sodium sulphide begins in a few 

 grains immediately. Complete gelatinization occurs in 

 about 5 per cent of the entire number of grains and 14 

 per cent of the total starch in 5 minutes; in about 10 

 per cent of the grains and 34 per cent of the total starch 

 in 15 minutes ; in about 22 per cent of the grains and 47 

 per cent of the total starch in 30 minutes ; in about 32 per 

 cent of the grains and 55 per cent of the total starch in 

 45 minutes; in about 37 per cent of the grains and 58 

 per cent of the total starch in 60 minutes. (Chart D 390.) 



The reaction with sodium salicylate begins imme- 

 diately. Complete gelatinization occurs in about 44 per 

 cent of the entire number of grains and 55 per cent of 

 the total starch in 5 minutes; in about 86 per cent of 

 the grains and 89 per cent of the total starch in 10 

 minutes ; in about 97 per cent of the grains and 99 per 

 cent of the total starch in 15 minutes. (Chart D 391.) * 



The hilum becomes distinct, attended by the forma- 

 tion of a very small bubble in most of the grains. The 

 lamellae are rather indistinct when the reagent is first 

 added but become more distinct as the reaction advances. 

 The grains become more refractive, the first part of the 

 grain to show this increased refractivity is a narrow band 

 about the margin. Gelatinization is preceded by a 

 pitted appearance at the distal end of the grain, and 

 begins at the corners of the distal margin. From these 

 points it spreads along the distal margin, and then toward 

 the proximal end. The starch becomes granular just 

 preceding gelatinization, and this process may advance 

 more rapidly on one side than on the other, or more 

 rapidly in the central part than on the margins. In 

 many grains 2 longitudinal fissures are seen to extend 

 upward from the distal margin toward the hilum, and 

 in such grains the portion between these fissures is 

 gelatinized more rapidly than that nearer the margin. 

 As the hilum is neared, in the progress of the reaction, 

 the bubble, which is usually present, and which has 

 been growing steadily larger, suddenly swells, then 

 shrinks and disappears and the hilum enlarges rapidly, 

 accompanying the rapid gelatinization of the marginal 

 material on either side. The proximal portion is the 

 last to be gelatinized and this may take place either 

 rapidly or rather slowly, and is usually accompanied 

 by considerable invagination of the capsule at this point. 

 In a very few grains the proximal margin is gelatinized 

 after the process of gelatinization has advanced about 

 halfway from the distal end to the hilum. In such grains 

 the most resistant part of the grain is just distal to the 

 hilum. The gelatinized grains are much swollen, have 

 rather thin capsules, and are very much distorted, retain- 

 ing little if any resemblance to the form of the untreated 

 grain. 



*The reaction with this reagent begins at the margin of the 

 grains of all species thus far studied. In the Iridaceee the reaction 

 is therefore more rapid in the grains in which the outline is more 

 uneven or in which the most abrupt corners appear. The group 

 of /. persica var. purpurea, I. eindjarensis, and /. pursind is the 

 moat resistant to this reagent, while it is the least resistant to most 

 of the reagents. The outline of the grains of this group is more 

 curved and possesses fewer inequalities than those of the other 

 species of this genus studied. 



