736 



DATA OF PROPERTIES OP STARCHES OF PARENT- AND HYBRID-STOCKS. 



14. PHAIUS. 



This genus of ornamental terrestrial orchids includes 

 about 15 species. There are many more hybrids than 

 species. The specimens were obtained from Sander and 

 Sons, St. Albans, England. 



Starches from the pseudobulbs of the following 

 parent-stocks and hybrid-stocks were studied : 

 42. P. grandifolius Lour. (Bletia tankervilliw R. Br.) (seed 



parent), R. wallichii Lindl. (P. grandifolius Lindl. ; P. 



licolor Lindl.; P. grandiflorus Reichb. f.) (pollen parent), 



and P. hybridus (hybrid). 



42. STARCHES OF PHAIUS GRANDIFOLIUS, P. WALLI- 



CHII, AND P. HYBEIDUS. 



PHAIUS GRANDIFOLIUS (SEED PARENT). 

 (Plate 23, fig. 136; Charts D 574 to D 594.) 



HISTOLOQIC PROPERTIES. 



In form most of the grains are simple and isolated 

 with the exception of a few which appear in aggregates 

 of usually 2, rarely 3, components. Compound and 

 semi-compound grains usually of 2, rarely of 3, com- 

 ponents are occasionally observed. Well-defined pressure 

 facets are not present. Most of the grains are regular, 

 although irregularities such as the following are moder- 

 ately frequent : (1) Either a small nipple-like excrescence 

 or protuberance at or near the proximal end, the former 

 sometimes inserted in a concave depression at this end; 

 (2) a long, blunt extension at or near the proximal 

 end; (3) shifting of the longitudinal axis, which is 

 usually slight, rarely abrupt; (4) a spicule-like excres- 

 cence, sometimes refractive, at the proximal end; (5) a 

 flared addition or excrescence, sometimes refractive, at 

 the distal end; (6) a concave indentation either at the 

 proximal or distal end; (7) slightly undulating margin; 

 and (8) secondary lamellae which are placed at varying 

 angles with the primary set. The conspicuous forms are 

 ovoid, often elongated, with broadened and squared distal 

 end ; pyriform with broadened distal end ; triangular with 

 rounded angles; and pure ovoid. Additional forms are 

 urn-shaped with flared distal margin; spindle-shaped, 

 pyriform with elongated proximal end, knob-, club-, boot-, 

 and bottle-shaped; and grains of indefinite shape. The 

 grains are flattened, some much more than others, and 

 when viewed on edge are usually narrow ellipsoidal with 

 squared distal end. 



The hilum is often not demonstrable, but when ob- 

 served is usually either a lenticular or round, non-refrac- 

 tive to slightly refractive spot, occasionally quite refrac- 

 tive. Either a small, longitudinal slit-like cavity, or a 

 short, transverse cleft is rarely present at the hilum. 

 One delicate, short fissure occasionally emerges from 

 either side of the hilum and is directed obliquely toward 

 the distal end, and rarely such fissures may be quite long 

 and so deflected as to become parallel with each other. 

 The range of eccentricity is about 0.16 to 0.024, com- 

 monly about 0.06 to 0.05, of the longitudinal axis. 



The lamella are generally demonstrable throughout 

 the entire grain, although they are less distinct and 

 finer near the proximal end, with the exception of a 

 narrow refractive band sometimes found at the distal 

 margin, in which they are either very fine or indistinct. 

 They can usually be detected directly around the hilum 

 either as elliptical, meniscus-shaped or circular rings, 

 but even in those close to the hilum the form becomes 



flattened on the distal side of this structure, so that over 

 most of the grain they are slightly cresccntic to straight, 

 being parallel with each other and with the distal margin ; 

 rarely they follow the outline of the grain. Most of the 

 lamella; are fine to moderately fine, but occasional excep- 

 tions are found in which they are moderately coarse over 

 the greater part of the grain. One very refractive lamella 

 is frequently located at varying distances from the hilum ; 

 and in most of the much elongated grains the finer la- 

 mellae are grouped between coarser refractive ones which 

 vary in number according to the length of the grain. 

 A narrow, refractive band is often found at the proximal 

 end which extends bilaterally, usually for about one-half 

 to two-thirds, occasionally the entire length, of the grain. 

 A group of undulating lamellae, either about the middle 

 or nearer the distal margin, is occasionally observed. 

 Secondary lamellae are moderately often present; they 

 are usually unilateral and more often located at right 

 angles either to the distal end or to about the middle of 

 the grain ; occasionally bilaterally located at the pointed 

 distal end, or unilateral and at right angles to the proxi- 

 mal end. The number on much elongated grains may 

 reach about 150, but generally about 100 on the common 

 large grains. 



The size varies from the smaller grains which are 

 about 5 by 4/t, to the larger which are 130 by 46/t, in 

 length and breadth. The common size is about 7-t by 

 40/A in length and breadth. 



POLARTSCOPIC PROPERTIES. 



The figure is usually very eccentric. The lines are 

 fine and intersect obliquely, they are straight in most 

 grains, but moderately often are slightly bent and some- 

 times bisected. A few double figures are present. 



The degree of polarization is high to very high (value 

 85). Variation is found in the different grains, and is 

 also often considerable in the same aspect of a given 

 grain, a portion of one quadrant often showing much 

 lower polarization than the other quadrants. 



With selenite the quadrants are generally well do fined, 

 unequal in size, and often slightly irregular in shape. 

 The blue is more often pure, although in many grains 

 it may lack purity throughout at least 1 quadrant; the 

 yellow is more often not pure throughout the quadrants. 

 The impurity is indicated at both ends of the scale, a 

 frequent orange tint to the yellow and an occasional 

 purplish tint to the blue caused by a low degree of 

 polarization, and either a greenish tinge or an iridescence 

 caused by very high polarization. 



IODINE REACTIONS. 



With 0.25 per cent Lugol's solution the grains color a 

 moderate blue-violet (value 50) at once, which deepens 

 rapidly, becoming more blue. With 0.125 per cent 

 Lugol's solution the grains color a light blue-violet, which 

 deepens rapidly, becoming more blue. After heating in 

 water until the grains are gelatinized and then adding 

 2 per cent Lugol's solution, the grains color a deep blue, 

 many with reddish tint, and the solution a moderately 

 deep blue. If the preparation is boiled for 2 minutes and 

 then treated with an excess of 2 per cent Lugol's solution, 

 the grain-residues, which are very few in number, become 

 a light to moderate blue with deep reddish tint, and the 

 capsules a deep reddish-heliotrope to a wine-red. 



