GENUS QtTERCUS. 



427 



Effects of Varioiis Reagents. — With chloral hydrate-iodine the reaction begins at once. A few 

 grains are gelatinized in 30 seconds, about nine-tenths in 2 minutes, practically all in 3 minutes, 

 and all in 5 minutes. The grains are much swollen and deeply colored, but retain the general shape 

 of untreated grains. The reaction is qualitatively the same as in Q. alba. 



The reaction with chromic acid begins immediately and all (except one in several hundred) are 

 dissolved in 25 seconds. These few scattered grains may resist solution for 50 seconds. The reaction 

 is qiialitatively the same as for Q. alba. 



With pyrogallic acid the reaction begins at once and is complete in 30 seconds. The gelatinized 

 grains are so much swollen and wrinkled that they do not usually resemble the shape of the untreated 

 grain. The reaction is qualitatively the same as in Q. alba. 



The reaction with ferric chloride begins in a few grains in a minute and all are in various stages 

 of gelatinization in 5 minutes. About half are gelatinized in 10 minutes and all but a few resistant 

 grains (one in several hundred) in 15 minutes. The reaction is generally complete in the latter in 

 30 minutes. The gelatinized grain is much swollen, but often retains the general shape of the un- 

 treated grain. It is more regular in outline than in Q. alba. The reaction is qualitatively the same 

 as in Q. alba, but during gelatinization small particles are not broken off with so much force from 

 the larger ungelatinized mass as in Q. alba. 



With Purdy's solution the hilum and central fissure swell slightly at once, but the subsequent 

 change is very gradual during 15 minutes. In 30 minutes much of the central portion of only a 

 very small percentage of the grains is gelatinized and there is little further progress in an hour. 

 Gelatinization proceeds along the main cleft, which is divided at the distal end into two or three 

 large branches. Radiating lines pass from the main fissure. Lamellae unnoticeable in an untreated 

 grain may be seen, but do not become very distinct. The reaction resembles that observed in the 

 grains of Q. texana, but the lamellae are not so well defined and gelatinization does not proceed so 

 far. When protuberances are present a separate center of gelatinization is found in each. The 

 gelatinized grains are swollen, but retain the shape of the untreated grain. The reaction is quali- 

 tatively the same as that noted for Q. alba, but does not proceed nearly so far. 



STARCH OF QUERCUS TEXANA. (Plate 12, fig. 68. Chart 68.) 



Histological Characteristics. — In form the grains are usually simple; a few compounds present 

 consist usually of two components. The grains are isolated,, except a few fountl in small aggregates 

 and many in clumps. The most conspicuous forms are 

 ellipsoidal, ovoid, and pyriform. Other shapes, also noted 

 in Q. alba, are present. The grains exhibit the same types 

 of irregular surface as those noted for Q. alba. 



The hilum is usually fissured, but occasionally it may 

 be a round cavity, which is centric or usually eccentric, 

 about one-third to two-fifths of the longitudinal axis. The 

 longitudinal cleft which proceeds from the region of the 

 hilum usually resembles a 2- or 3-pronged fork. If but one 

 cleft starts from the hilum it usually soon divides into the 

 two or three main branches. There is quite often a short, 

 transverse fissure at the hilum or a little below it. The 

 arrangement of the clefts is practically identical with that 

 found in the grains of Q. rubra, but they are usually deeper 

 and more often have radiating fissures. In the somewhat 

 bean-shaped, and in the triangular grains, a single fissure 

 similar to that of Q. alba is usually present. 



The lamellcB are not generally demonstrable. Rarely 

 8 have been counted, which are seen to be identical in 

 character to those of Q. alba. 



The size varies from the smaller, which are 4 by 3/i, to the larger elongated grains, which are 20 by 

 14/u, and the bean-shaped, which are 26 by 15;u in length and breadth. The common size is 12 by 7 ft. 



Polariscopic Properties. — The figure is usually eccentric, and the bean type seen in Q. alba is 

 also found. The lines usually intersect obliquely and are more often bent or Ijisected than in Q. 

 rubra, but not so frequently as in Q. alba. 



CI PA CA 

 POPS 



MIMUTtS 



Curve of Reaction-IntenBitiea of Starch of Quercua texana. 



