GENUS ARUM. 



445 



The reaction with Piirdy's solulion begins in some grains at once and is general in 30 seconds. 

 About half are gelatinized in 8 minutes and the others are in all stages of gelatinization. The reac- 

 tion is similar to that with pyrogallic acid. 



Differentiation of Certain Starches of the Genus Ariini. 



Histological Characteristics. 

 Conspicuous Forms. 

 A. palceslinum: Simple, mostly isolateil. Dome-shaped 

 and hemispherical, with two or tliree or more 

 facets at distal end, triangular and splierical. 

 A . comutum: Essentially the same as in ^-1 . palcedinum but 

 the conspicuous forms are spherical, ovoid, dome- 

 shaped, hemisplierical, and triangular. 

 A. italicum: Essentially the same as in A. palmstinum. 



Hitum Form, Number, and Position. 

 A. pahestinum: Form fairly distinct, small, round, single; 

 rarely fissured. Position usually slightly eccentric. 

 A. comutum: Form same as in .4. paloestinum. Position 



usually shghtly eccentric. 

 A. italicum: Form not distinct, large round, single; rarely 

 fissured. Position usually slightly eccentric. 



Lamella General Characteristics and Number. 

 A. palceslinum: Not very distinct, concentric rings; may 



or may not follow outline of margin, one prominent 



in region of hUum. 8 appro.\imately on larger grains. 

 A. comutum: Very distinct, coarse, concentric rings, may 



or may not follow outline of margin ; two lamellae 



usually very distinct ; sometimes two sets of lamel- 

 lae. 10 to IG on larger grains. 

 A. italicum: Indistinct; only some near hilum visible; 



coarse, regular, concentric rings. Number not 



determinable. 



Size. 

 A. palcestinum: From 2 to 20m, commonly 14/i. 

 A. comutum: From 2 to 24^, commonly 15/^. 

 A. italicum: From 2 to 16;i, commonly 10^. 



PoLARiscopic Properties. 



Figure. 



A. palcestinum: Usually eccentric, clear-cut, regular in 



shape, in form of a cross. 

 .4. comutum: Same as in /I. palcestinum. 

 A. italicum: Same as in A. palcestinum. 



Degree of Polarization. 

 A. palcestinum: Fair. 

 .4. comutum: Fairly high. 



A. italicum: Fair, higher than in A. palcestinum, and lower 

 than in .4. cornutum. 



Polarization ivith Selenite Quadrants and Colors. 



A. palcEstinum: Quadrants well-defined, and generally reg- 

 ular in size and shape. Colors not pure. 



A. comutum: Quadrants same as in^.patesfwium. Colors 

 quite pure. 



A. italicum: Quadrants same as in .4. pates(mu(i. Colors 

 fairly pure. 



Iodine Reactions. 

 Intensity and Color. 



A. palcestinum: Deep; blue-violet. 



A. cornutum: Deep, deeper than in other .4rum starches; 

 blue- violet. 



Iodine Reactions. Continued. 

 Intensity and Color. Continued. 

 .4. italicum: Deep, the same as in /I. palcestinum; blue- 

 violet. 



Staining Reactions. 

 With Gentian Violet. 

 A. palcestinum: Light. 

 A. comutum: Fairly deep to deep, much deeper than in 



A. palcestinum. 

 A. italicum: Light, same as in /I. palcestinum. 



With Safranin. 

 A. palcestinum: Light. 



A. cornutum: Fairly deep, much deeper than in A. palces- 

 tinum. 

 A. italicum: Very light, less than in A. palcestinum. 



Temperature of Gelatiniz.\tion. 

 A. palcestinum: 70 to 71 C, mean 70..5. 

 .4. cornutum: 69.5 to 70.5 C, mean 70. 

 A. italicum: 71 to 73 C, mean 72. 



Effects of Various Reagents. 

 Reaction with Chloral Hydrate-Iodine. 

 A. palcestinum: Begins in a minute; complete in 8 min- 

 utes. 

 A. comutum: Begins in 30 seconds; complete in 5 min- 

 utes. 

 A. italicum: Begins in 30 to 00 seconds; complete in 27 

 minutes. 



Reaction with Chromic Acid. 

 A. palcestinum: Begins in 30 seconds; complete in 10 min- 

 utes. 

 A. comutum: Begins in 30 seconds; complete in 6 minutes. 

 A. italicum: Begins at once; complete in 5 minutes. 



Reaction with Pyrogallic Acid. 

 A. palcestinum: Begins in 2 minutes; complete in 15 min- 

 utes. 

 A. cornutum: Begins in 30 seconds; complete in nearly all 



in 30 minutes. 

 A. italicum: Begins in 30 to 60 seconds; complete in 7 

 minutes. 



Reaction with Ferric Chloride. 



A. palcestinum: Begins in 2 minutes; complete in 30 min- 

 utes. 

 .4 . cornutum: Begins in a minute; complete in 12 minutes. 

 .4. italicum: Begins in a minute; complete in 10 minutes. 



Reaction with Purdy's Solution. 



A. palcestinum: Begins in 10 minutes; half affected, a few 

 completely gelatinized in 2 hours. 



A. cornutum: Begins in 30 seconds; half affected and com- 

 pletely gelatinized in 15 minutes; no further reac- 

 tion in 60 minutes. 



A. italicum: Begins in 30 seconds; all are affected and half 

 completely gelatinized in 8 minutes, the others par- 

 tially gelatinized. 



NOTES ON THE ST.A.RCHES OF ARUM. 



The same type of starch-grain is exhibited by all of the Arums, and also by Arisoema and Dra- 

 cunculus, which are closely related genera and formerly included among the former. The three 

 starches are very closely in accord in their histological peculiarities. The differences in the degree 

 of polarization are insignificant, but in the other reactions there are more or less significant vari- 

 ations, even with Purdy's solution, which acts verj' slowly. Each species can be readily distinguished 

 from the others bj' peculiarities of the reactions. 



