34 



HISTOLOGIC PROPERTIES AND REACTIONS. 



to diverge, showing at the end of 60 minutes a differ- 



, E I I per cent in the total starch gelatinized. In 



the reactions with chromic acid, pyrogallic acid, copper 

 nitrate, and cupric chloride the greatest differences 

 are noted at the end of the 5-minute period, and in the 

 mercuric-chloride reactions at the end of 60 minutes.* 



The curves of the hybrids Brunsdonna sandem alba 

 and B. sanderce likewise tend to keep close together in 

 more than half <>f the reactions, and in even a larger 

 numher than in the parents. Tendency to a well-marked 

 separation of the two hyhrid curves is seen in the reac- 

 tions with sodium hydroxide, sodium sulphide, calcium 

 nitrate, uranium nitrate, and copper nitrate. There is 

 not a constant relationship of the parental and hybrid 

 curves; for instance, the parental curves may be very 

 i lose to one another, while the hybrid curves are well 

 separated from them and even from each other, as in the 

 latter case, in the sodium-sulphide reactions; or all 

 four curves may he well separated, as in the calcium- 

 nitrate reactions; or the parental curves may be fairly 



* Notes on the Reactive-Intensities of the Brunsdonnce Starches. — 

 The reactions of these starches have been found at times to be quite 

 erratic, especially with sodium hydroxide and potassium sulphide, and 

 they appear to be affected by variations in temperature, pressure, 

 and humidity and certain other attendant conditions to a marked 

 , whereas most if not all other starches studied are either but 

 very little or not at all influenced by corresponding conditions. There 

 may be considerable variation in the percentage-gelatinization at 

 different parts of the slide, so that it is always quite important that 

 the observations with these starches be made in center of the field 

 even though the cover-slip be sealed in the manner stated in Chapter 

 II. Sometimes the reaction appeared to be more rapid at the margin 

 of the cover and at other times at the central part of the preparation. 

 Then again, where the grains are crowded the reaction appeared to 

 be considerably retarded. The crowding may be apparent, particu- 

 larly in clumps of grains that have been massed after the addition 

 of the reagent. 



Table A 1. 



