PREFACE. 



XI 



be associated with variations in another, and that when 

 variations in different properties are coincidently ob- 

 served they may be of like or unlike character. Gela- 

 tinizability is one of the most conspicuous properties of 

 starch and it represents a primary physico-chemical unit- 

 character, which character may be studied in as many 

 quantitative and qualitative phases as there are kinds 

 of starches and kinds of gelatinizing reagents, the phe- 

 nomena of gelatinization by heat being distinguishable 

 from those by a given chemical reagent, and those by 

 one reagent from those by another, and those of one 

 starch by a given reagent from those of another starch. 

 The gelatinization of the starch grain is certainly not, 

 as is commonly supposed, a manifestation of a simple 

 process of imbibition of water, such as occurs in the 

 swelling of particles of dry gelatin or albumin, but in 

 fact a very definite chemical process corresponding to 

 that which occurs in the swelling of liquid crystals, and 

 which must vary in character in accordance with the 

 reagent entering into the reaction. It therefore follows, 

 as a corollary, that the property of gelatinizability of 

 any specimen of starch may be expressed in as many 

 independent physico-chemical imit-character-phases as 

 there are reagents to elicit them. By these methods 

 both physico-chemical unit-characters and unit-character 

 phases can be reduced to figures, from which charts can 

 be constructed which show in the case of each starch 

 that the sum total of these values is as distinctive of the 

 kind of starch and plant source as are botanical characters 

 of the plant. 



" Individualities of one or the other of the parental 

 starches may or may not be observed in the starch of 

 the offspring, and if present they may or may not appear 

 in modified form. Moreover, the starch of the offspring 

 may exhibit peculiarities that are not seen in either of 

 the parental starches, and when two or more sets of 

 hybrids have resulted from separate crosses of the same 

 parental stock, each lot of hybrids may not only exhibit 

 in common distinctive variations from parental charac- 

 ters but also independent individualities, and, as a corol- 

 lary, differ, from each other in well-defined respects. 

 Hence, not only may a given hybrid be definitely attached 

 to definite parentage, but also the hybrids of separate 

 crosses may be recognized as such. 



" The studies of the starches of parent- and hybrid- 

 stocks have been supplemented by corresponding and 

 somewhat laborious histological examinations of plant 

 tissues associated with some macroseopical inquiry. The 

 resulia of this supplementary research are in striking 

 accord with those of the starch investigations, and both 

 are in entire harmony with universally recognized prin- 

 ciples of the plant and animal breeder and with the dic- 

 tum underlying these researches, 'vital peculiarities 

 may be resolved to a physico-chemical basis ' — with 

 which may be coupled a second dictum, ' corresponding 

 complex organic substances exist in stereoisomeric forms 

 that are modified specifically in relation to and diag- 

 nostic of the protoplasmic source.' " 



While the present research treats almost solely of 

 the properties of parent-stocks and hybrid-stocks, and 

 correspondingly of heredity, it will be found that the 

 results can be utilized in very broad applications to 

 biology. Apart from the derogation of intermedi- 

 ateness as a criterion of hybrids, there is perhaps no 

 single feature of the report that will appeal more 

 immediately to biologists in general than the facts that 

 have been collated that indicate a far greater degree 

 of importance of hybridization in the genesis of 

 species and evolution than has thus far been recog- 

 nized. Moreover, to every student who has kept 

 abreast of the developments of modern biologic science 

 it must be evident that the great advances now fore- 

 shadowed seem to be inseparably associated with 

 physics and physical chemistry ; and from the resiilts 

 of these researches on the physical chemistry of 

 starches and hemoglobins it seems that it may with 

 safety be predicted that the principles and methods 

 herein presented will serve as one of the essential 

 starting-points that will certainly lead to results of 

 great if not epochal importance. What physics prom- 

 ises in explanation of the phenomena of organic 

 growth and form, physical chemistry promises in the 

 explanation of organic function. 



Finally, an apologetic word may not be amiss. 

 This investigation like its two predecessors has been 

 pursued amidst the endless interruptions and discon- 

 certions that are inseparable from the exactions of 

 professorial duties and other unavoidable conditions, 

 and not infrequently it has of necessity been set aside 

 for weeks or months. This obviously has not only 

 somewhat but seriously interfered with that continu- 

 ity of work and thought that is so important in the 

 successful pursuit of elaborate investigations in un- 

 explored fields of inquiry. On this account there 

 will appear not a little evidence of a lack of uniformity 

 of treatment of corresponding parts of the work ; an 

 absence here and there of sufficient and careful detail, 

 correlation, and analysis; and a failure not infre- 

 quently to discuss with sufficient fullness many facts 

 in their biologic relationships and applications. 

 Moreover, inasmuch as the writer is not a botanist, 

 some facts that may be of especial botanic interest 

 may not have been given adequate treatment, while 

 some of minor interest may have been unduly 

 accentuated. 



Edward Ttsott Eeicheet. 

 From the S. Wei/r Mitchell Laboratory of Physiology, 

 University of Pennaylvania. 



