GENTTS VALLOTA. 



633 



GENUS VALLOTA. 



This genus, like Amaryllis, has but a single species, Vallota purpurea Herb. It is the South 

 African representative of the American Hippeastrum, and is cultivated under the name of the Scar- 

 borough lily. It is closely related to Cyrtanthus, another South African genus, and it has been 

 suggested that Vallota be classified as a subgenus oi Cyrtanthus. 



STARCH OF VALLOTA PURPUREA. (Plate 51, figs. 305 and 306. Chart 211). 



Histological Characteristics. — In form the grains are usually simple. There are occasionally 

 compounds and aggregates consisting of two or three components. Rarely pressure facets are 

 seen on the isolated grains. There are no clumps. The surface of the grains is usually somewhat 

 irregular, owing chiefly to inequalities in the development of the various parts. There are sometimes 

 seen two or three grains of unequal size, generally arranged in linear fashion, which have been pressed 

 together and then later inclosed by several lamellae. The conspicuous forms are spherical ovoid 

 to spherical, spherical forms with very slight irregularities, ovoid, quadrilateral and triangular 

 with very much rounded angles. There are also elliptical, elliptical with a broad, squared distal 

 end, dome-shaped, oval, round, and various irregular forms. The grains are not flattened and there- 

 fore are as thick as broad. 



The hilum is a distinct, rather large, round or rarely eUiptical spot, eccentric from two-fifths to 

 one-fourth, usually about one-third, of the longitudinal axis, and in or to one side of the median line. 

 There may be 2, 3, or 4 hila linearly arranged, usually parallel to the transverse axis of the grain. 

 The hilum may have a fissure, which is usually single, transverse or diagonal, straight or singly 

 curved, often bisected or ragged at the ends. There is also sometimes a stellate or irregular arrange- 

 ment of fissures at the hilum. 



The lamellce are distinct, rather fine, often irregular circles or ellipses or arcs of circles which 

 may or may not be continuous. Those near the hilum do not always correspond in shape to the 

 outline of the margin. Those near the margin often appear to have been added at a different time 

 from those near the hilum, and their longitudinal axis often does not coincide with that of those 

 near the hilum. The former are not so fine as those near 

 the hilum, but are distinct and do not vary much in dis- 

 tinctness in different grains. There are 12 to 14 lamella 

 on the larger grains. 



The grains vary in size from 3 to 30n. The common 

 size is 18iu. 



Polariscopic Properties. — The figure is usually mark- 

 edly eccentric, distinct, but not clear-cut. Its lines are 

 broad and tend to become broader and poorly defined as 

 they near the margin; they are sometimes somewhat bent 

 and otherwise distorted; and often they are placed at vary- 

 ing angles to one another, causing the figure to be irregular. 



The degree of polarization is high. It varies some- 

 what in different grains, but not much in different aspects 

 of the same grain. It is sometimes lower near the margin 

 of the same aspect of a grain than near the hilum. 



With selenite the quadrants are not well defined, are 

 irregular in shape, and unequal in size. The colors are 

 usually pure. 



Iodine Reactions. — With 0.25 per cent Lugol's solu- 

 tion the grains color a fair blue- violet and the color deepens quite rapidly; with 0.125 per cent solu- 

 tion they color lightly, but the color deepens fairly rapidly. After heating in water until the grains 

 are completely gelatinized, the solution colors lightly and the grains very deeply on the addition of 

 iodine. After boiling for 2 minutes the solution colors deeply, but the grain-residues generally lightly 

 or not at all. With an excess of iodine the capsules color a red-violet and about half of them retain 

 more or less blue-reacting starch, especially at the proximal end. 



Staining Reactions. — With gentian violet the grains begin to stain in 2 minutes and in 30 minutes 

 are fairly stained, one as much as another. 



QartNo. 211. 



I GV 

 S 



CI CA PA FC 



PS CI PA ' 

 ■~ PC PS 



Curve of Reaction-Intensities of Starch of Vallota 

 purpurea. 



