798 STARCHES OF CANNACEiB. 



STARCHES OF CANNACE/E. 



Class, Monocotyledones. Order, Scitaininales. Family, Cannacese. Genus, Canna. 



GENUS CANNA. 



The cannas, popularly known as the Indian shot plant, because of the small, round, shot-like 

 seeds, are ornamental, herbaceous plants that are natives of the tropics and semi-tropics of both 

 hemispheres and now cultivated extensively in a number of countries as foliage plants and for other 

 economic purposes. There are a number of tribes or types, species, varieties, and horticultural 

 forms, and during comparatively recent years the evolution of the latter by hybridization, by cross- 

 ing hybrids, etc., and by selection and cultivation has gone on to so great a degree that a very large 

 number of forms are offered by the trade. It is quite impossible in most cases to properly refer these 

 forms to either the actual, inunediate, or remote parentage. The tuberous roots are rich in starch, 

 and in some countries the canna is cultivated especially for this substance, or for the roots, which are 

 eaten as a vegetable. The well-known arrowroot, Tous-les-mois (see Marantacece, page 813), is 

 attributed to Canna edidis, a native of tropical America. The starches of the cannas are in the form 

 of exceptionally large, markedly lamellated grains, which render them especially useful for the study 

 of starch-properties. Starches from ten som-ces were examined, including the following: C. wars- 

 zewiczii Dietr., a native of Costa Rica, is a well-marked species, and one of only two of this list 

 that are recognized as such; C. roscoeana Bouche is referred to C. lutea Miller; C. rmLsoefolia we have 

 not been able to indentify; C. edulis Ker. (C. esculenta Lodd.), a well-defined species, is a native of 

 tropical America; C. var. (Konigen Charlotte), C. var. (President Camot), C. var. (L. E. BaUy), 

 C. var. (Mrs. Kaie Grey), C. var. (Jean Tissot), and C. var. (/. D. Eisele) are cultural forms and 

 probably hybrids of some kind and of varied source. 



STARCH OF CANNA WARSZEWICZII. (Plate 82, figs. 491 and 492, Chart 335.) 



Histological Characteristics. — In form the grains are usually simple and isolated. A few com- 

 pound grains consisting of two components are present, characterized by two hila and a more or 

 less well-defined depression or fissiu-e at the line of union of the two grains. There are no pressure 

 facets. There is some irregularity of outline which tends to be most conspicuous in the region of 

 the hilum. The most conspicuous forms are the broad ovoid and clam-shell tjrpe. The peculiar 

 formation of the latter seems to be the result of a tendency to the formation of lateral depressions 

 at each side of the hilvun, which is associated with a shortening of the long diameter of the large, 

 ovoid grains. In some ovoid grains the depression is unilateral and others bilateral, thus giving 

 rise to the appearance of an extrusion of the part of the grain on which the hilum is located. Be- 

 tween the best-defined, broad ovoid, and clam-shell types of grains there are all transitional forms — 

 oval, reniform, pyriform, cylindrical, circular, quadrangular, triangular, and irregular. Viewed on 

 edge, the grains are seen to be flattened, elliptical, or ellipsoidal, and one end may be thicker than 

 the other, rendering them somewhat prismatic. 



The hilum is a small, distinct, circular, eccentric spot, near or on the margin, and slightly to 

 the right or left of the longitudinal axis. Occasionally the hilum is elongated instead of circular, 

 and a grain of an elongated, flattened form is noted rarely, which has the hilum centrally located. 

 Fissuration is sometimes noted in the region of the hilum, and similar fissures may be seen in other 

 parts of the same or other grains. In the conspicuous grains 2 hila are present; in some apparently 

 single grains 3 or 4 hila are linearly arranged. 



The lameUcB are very distinct, generally coarser and more distinct near the hilum than near the 

 distal margin and more distinct in some grains than in others. They are coarse, regular rings about 

 the hilum, and arcs of circles beyond which are probably continuous and follow very closely the out- 

 lines of parts of the grain distal to the hilum. They are arranged so that 1 or 2 very large, coarse 

 lamellffi alternate with a group of very fine, rather indistinct lamellae. On a large grain the average 

 number is 48 to 50. 



The grains vary in size from 15 to 70ai. The common size is about 50^1. The large, ovoid 

 grains range from about 45 by 30/;* to 72 by OO/t in length and breadth, and the clam-shell type 

 from 40 by 40/t to 50 by 40/1 in length and breadth. In some of the latter the longitudinal diameter 

 is shorter than the transverse diameter. 



