RICHARDIA — MUSA. 



725 



two. In this reaction R. mrs. roosevelt shows qualita- 

 tively a closer resemblance to li. albo-maculata than to 

 R. elliottiana, but there are very little differences in the 

 reaction of the three starches. 



The reaction with sodium salicylate begins imme- 

 diately. Complete gelatinization occurs in about 89 per 

 cent of the entire number of grains ami '.H per cent of 

 the total starch in 3 minutes; in about !»'.) per cent of the 

 grains and more than 99 per cent of the total starch in 5 

 minutes; complete gelatinization occurs in 100 per cent 

 in 10 minutes. (Chart D 552.) 



The hilum becomes distinct as in R. albo-maculata. 



No lamella? are visible. Gelatinization begins more fre- 

 quently at the distal corners of the pressure facets than 

 in either parent, and rarely, at the hilum, and in this ie 

 nearer to R. albo-maculata than to R. elliottiana. The 

 progress of gelatinization in each case is the same as thai 

 described under /.'. albo-maculata. The gelatn 

 grains are large and considerably distorted, the same as 

 R. albo-maculata. In this reaction B. mrs. roosevelt 

 shows qualitatively a somewhat closer relationship to 

 R. albo-maculata than to li. elliottiana, though but few 

 differences are to be seen in the reactions of the three 

 starches. 



13. MUSA. 



The genus Musa includes about 20 species of tropical 

 plants that are widely distributed, especially in the tropi- 

 cal regions of the Old World. Some of the species ami 

 varieties are extensively cultivated. Starches of the 

 following parent-stocks and hybrid-stocks were studied : 



41. M. arnoldiana Horfc. (seed parent), M. gillctii Hort. 

 (pollen parent), and M. hybrida (hybrid). 



The specimens were obtained from the growers, 

 Ilaagc and Schmidt, Erfurt, Germany. 



41. Starches of Musa arnoldiana, M. gilletii, 

 and M. hybrida. 



Musa arnoldiana (Seed Parent). 



(Plate 23, fig. 133; Charts D 553 to D 573.) 

 Histologic Properties. 

 In form the grains are usually simple and isolated, 

 only a very few compound grains and no aggregates are 

 seen. The compound grains belong to but one type: 2 

 small simple grains at the proximal end of a large grain, 

 all being surrounded by 20 to 30 common secondary 

 lamellae. An occasional isolated grain is seen which 

 has a pressure facet on the distal end, indicating pre- 

 vious existence as part of an aggregate. The grains are 

 usually moderately regular in form, and any irregulari- 

 ties are due to the following causes: (1) A greater de- 

 velopment of one part of the distal end than the rest; 



(2) a deviation of the longitudinal axis at the center or 

 at the distal end, and a consequent bending of the grain ; 



(3) notches and other shallow or deep depressions in the 

 margin, usually at the distal end; (4) a secondary set of 

 lamella? whose longitudinal axis is at an angle, usually 

 about 90°, with that of the primary set; (5) small nipple- 

 like or larger pointed projections, usually from the proxi- 

 mal end. The conspicuous forms are triangular with 

 curved base and rounded angles, short and elongated 

 elliptical, and ovoid with flattened distal end. The addi- 

 tional forms are oyster-shell-shaped, pyriform, lenticular, 

 irregularly polygonal, and quadrilateral forms with 

 rounded angles. When viewed on edge all the larger 

 grains are very much flattened and have an irregular 

 rod-shape. Many of the grains of this specimen are 

 deeply fissured, the fissures having no relation to the 

 hilum; and many also show erosions of the margin at the 

 distal end. 



The hilum is a distinct, round or lenticular spot which 

 is rarely fissured. The fissures when they are present 

 have the following forms: (1) An irregularly stellate 

 arrangement of many short fissures; (2) a small, single, 



straight, transverse or oblique lino. The hilum is eccen- 

 tric from 0.35 to 0.13, usually 0.23, of the longitudinal 

 axis. 



The lamellai are distinct, rather fine rings which near 

 the hilum and in the proximal half of the grains are 

 regular, continuous, and round or oval in shape. In the 

 rest of the grain they have the form of the outline of the 

 grain, often more or less modified; they are not so line, 

 and often show a wavy outline and become discontinuous 

 as they near the distal end. There is usually 1 ami some- 

 times 2 to 5 or G very refractive, coarse lamella? which 

 either form a band across the distal two-thirds of the 

 grain ami separate the line proximal from the less line 

 distal lamella^, or divide the fine lamella? into bands of 

 varying breadth. The number counted on the larger 

 grains varies from 20 to 42, commonly 30. 



In size the grains vary from the smaller which are 

 6 by 6fi, to the larger broad forms which arc 44 by 56/t, 

 and the larger elongated forms which are 48 by 20/t, in 

 length and breadth. The common sizes are 30 by 32/* 

 and 30 by 28/*. 



Polariscopic Properties. 



The figure is distinct and usually not well defined, 

 especially near the margin. The lines cross at acute 

 angles of widely varying size. They are often bent ami 

 sometimes bisected, and at times each is divided into 4 or 

 5 lines near the margin. 



The degree of polarization varies from low to high 

 (value 40). In most of the grains it is moderate, in a 

 few it is low, and in fewer it is high. There is consider- 

 able variation in a given aspect of an individual grain. 



With selenite the quadrants are usually not clear-cut. 



They are very unequal in size and often irregular in 



shape. The colors are usually not pure, and the yellow 



is less pure than the blue, but in a few grains both are 



pure. 



Iodine Reactions. 



With 0.25 per cent Lugol's solution the grains all 

 color a moderate blue-violet (value 55). The color 

 deepens very rapidly until it is very deep and more bluish. 

 With 0.125 per cent Lugol's solution the grains all 

 color lightly to moderately ami the color deepens rapidly, 

 more rapidly in some grains than in others. After beat- 

 ing in water until the grains are all gelatinized, and then 

 treating with 2 per cent Lugol's solution, the grains 

 all color a light or a light to moderate indigo, and the 

 solution a very deep indigo. If the preparation is boiled 

 for 2 minutes and then treated with an excess of a 2 

 per cent Lugol's solution, the grain-residues usually do 



