760 



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



minutes ; in about 88 per cent of the grains and 97 per 

 cent of the total starch in 45 minutes ; in about 93 per 

 cent of the grains and 99 per cent of the total starch in 

 GO minutes. (Chart D 613.) 



The reaction with barium chloride begins in a few 

 grains immediately. Complete gelatinization occurs in 

 about 0.5 per cent of the grains and 10 per cent of the 

 total starch in 5 minutes; in about 5 per cent of the 

 grains and 20 per cent of the total starch in 15 minutes; 

 in about 7 per cent of the grains and 25 per cent of the 

 total starch in 30 minutes; in about 10 per cent of the 

 grains and 30 per cent of the total starch in 45 minutes ; 



in about 16 per cent of the grains and 33 per cent of the 

 total starch in 60 minutes. (Chart D 614.) 



The reaction with mercuric chloride begins imme- 

 diately. Complete gelatinization occurs in about 45 per 

 cent of the entire number of grains and 75 per cent 

 of the total starch in 5 minutes ; in about 75 per cent of 

 the grains and 90 per cent of the total starch in 15 

 minutes; in about 82 per cent of the grains and 97 per 

 cent of the total starch in 30 minutes; in about 85 per 

 cent of the grains and 98 per cent of the total starch in 

 45 minutes; in about the same percentage of both the 

 grains and total starch in 60 minutes. (Chart D 615.) 



16. CYMBIDIUM. 



This genus of tropical, terrestrial orchids includes 

 about 30 species. There are only a few varieties and 

 hybrids. Starches from the pseudobulbs of the following 

 parent-stocks and hybrid-stocks were studied : 



44. C. lowianum Reiclib. f. (9eed parent), C. cburncum Lindl. 

 (pollen parent), and C. cburnco-lowianum (hybrid) . 



The specimens were obtained from Sander and Sons, 

 St. Albans, England. 



44. Starches of Cymbidium lowianum, C. 

 ebunnel'm, and c. ebueneo-lowianum. 



Cymbidium lowianum (Seed Parent). 



(Plate 24, fig. 142; Charts D G16 to D 618.) 

 Histologic Properties. 

 In form the grains are usually simple and isolated, 

 with the exception of a moderately small number which 

 appear in aggregates consisting of from 2 to 8 compo- 

 nents. Compound grains, usually consisting of 2 com- 

 ponents, are rarely observed. The majority of isolated 

 grains seem to have arisen and continued to exist as 

 such, and may be distinguished tentatively as a disaggre- 

 gate type; but a moderately large proportion are sepa- 

 rated components of aggregates, and hence may be 

 referred to as an aggregate type. Well-marked pressure 

 facets are present on the separated grains. The surface 

 is usually regular. Irregularities may occur which are 

 due chiefly to a shifting of the longitudinal axis ; to a 

 broad rounded swelling at one side that is apparently 

 formed by a secondary set of lamellae ; to a small concave 

 depression, probably a pressure facet, which may appear 

 at indefinite points on the surface ; to a flattening of one 

 side of the grain; and to slight irregular prolongations 

 at the corners of pressure facets. The conspicuous forms 

 among the isolated grains of the disaggregate type are 

 ovoid, ellipsoidal, pyriform, nearly round, club-shaped, 

 and rounded triangular. The conspicuous forms among 

 the isolated grains of the aggregate type are high and 

 low dome-shaped with squared, pointed or diagonal distal 

 end; bell-jar shape, polygonal, finger-shaped, and ovoid 

 with concave distal end. Very rare large isolated grains 

 of the disaggregate type are scattered amongst those 

 already noted. They are usually either ovoid or pyriform 

 in shape. The conspicuous forms among the aggregates 

 are mosaics of from 5 to 8 components ; doublets of equal 

 and unequal components ; triplets and quadruplets more 

 often of compact but sometimes of linear arrangement. 

 The grains are not, as a rule, flattened. 



The hilum is usually demonstrable as a round or 

 lenticular spot, which is usually non-refractive and but 

 slightly refractive in a few grains. A small rounded or 

 somewhat irregular cavity is sometimes found. Fissures 

 are not usually present either at or proceeding from the 

 hilum. The position of the hilum varies from centric to 

 quite eccentric, the range of eccentricity being usually 

 from 0.42 to 0.14, more often 0.25 to 0.15, of the longi- 

 tudinal axis. 



The lamellce are frequently not distinct, and can be 

 determined on a minority of the grains. When demon- 

 strable they appear as moderately fine, circular or lenticu- 

 lar rings when located near the hilum, but when a short 

 distance outward they assume the form of the grain. One 

 lamella placed at varying distances from the hilum is 

 more distinct than the others. A moderately refractive 

 border in which the lamella? are not demonstrable is 

 occasionally observed ; and a swelling located at right 

 angle to the primary lamella? appears to consist of a 

 secondary set of lamella?. On the larger grains 12 to 16, 

 more often 14, can be counted. 



The size of the grain varies from the small isolated 

 disaggregate grains which are 3 by 2/x, to the larger iso- 

 lated disaggregate grains which are 28 by 18/*, in length 

 and breadth ; the common size is about 20 by 14/*. The 

 isolated aggregates vary from about 5 by 4/* to 20 by 16/*, 

 commonly about 12 by 11**. 



PoLARiscoric Properties. 



The figure varies from centric to quite eccentric, the 

 latter in the majority of the grains. The lines in most 

 of the grains intersect obliquely ; they are fine and usually 

 straight, often broadening towards the margin in the 

 larger grains. Double and multiple figures are observed. 



The degree of polarization is high (value 80). There 

 is very little variation in the different grains, and prac- 

 tically no variation in a given aspect of a grain. 



With selemte the quadrants are sharply defined; 

 usually slightly to quite unequal in size, and more often 

 regular in form, sometimes somewhat irregular. The 

 colors are generally pure. 



Iodine Reactions. 

 With 0.25 per cent Lugol's solution the grains color 

 a moderate blue-violet (value 50), which deepens some- 

 what rapidly to a considerably darker color having a 

 more bluish tint. With 0.125 per cent Lugol's solution 

 the grains color a light blue-violet, which deepens some- 

 what rapidly to moderate, with a slightly more bluish 

 tint. After heating in water until all the grains are 



