Title: The American florist : a weekly journal for the trade
Identifier: americanfloristw3008amer (find matches)
Year: 1885 (1880s)
Authors: American Florists Company
Subjects: Floriculture; Florists
Publisher: Chicago : American Florist Company
Contributing Library: UMass Amherst Libraries
Digitizing Sponsor: Boston Library Consortium Member Libraries

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igo8. The American Florist. 221 mutations can be expected to give but few novelties of real worth. Degressive ond retrogressive mutations are confined to rather narrow lines, and will probably produce and reproduce certain definite variations of little economic value. In floriculture they may be of value where slight dillVrcnccs in color and other minor characters are important; but there will probably be little cliangc in the factors which go to make up quality in agricultural productions. Mendel perceived that if progress was to be made in the study of heredity the problem must be simplified as much as possible. There were two things es- pecially necessary to be controlled, in Buch experimental work; namely, ac- cidental mixtures due to crossing, and differences in too many characters. The common garden pea fulfilled these de- mands. It could be self-fertilized gen- eration after generation without deterio- ration, and varieties were found that dif- fered from each other in but few char-' acters. Mendel selected varieties of the pea which ditt'ered from each other in sucli characters as "round or wrinkled seeds," "yellow or green cotyledons" or seed leaves, and "purple or white flowers." These varieties he found to be true to their characters by inbreeding. He then crossed them once and made careful records of their progeny when in- bred for a number of succeeding genera- tions. His results may be stated as fol- lows: If two contrasted characters which have previously bred true are crossed, one only, the dominant char- acter, appears in the hybrid. (The Law of Dominance.) In succeeding generations, self-ferti- lized plants grown from seeds of this cross reproduce both characters in the proportion of three of the dominant character to one of the recessive char- acter. Furthermore, the recessive char- acter continues ever after to breed true; while those plants bearing the domi- nant character are one-third pure domi- nants which ever after breed true to the dominant character, and two-thirds hy- brid dominants which contain the re- cessive character in a hidden condition. (Mendel's Law of Inheritance.) The theory supposes that on the average 50 per cent, of the germ cells will bear the dominant character and 50 per cent, will bear the recessive character. Now, if we could pick out at random any 100 pollen or male cells to fertilize any 100 egg or female cells we can see that there are equal chances for four results. A D male cell might meet a D female cell, a D male cell an E female cell, an R male cell a D female cell, and an R male cell an R female cell. We have (D-fD), (D-fR), (R+D) and (R+R) formed in equal quantities, but as the two middle terms are the same, we can reduce the formula to one (D+D) to two (D+R) to one (R+R), But wherever there is a D present in the germ cell, the dominant character shows while the recessive character is hidden. The one part or the 25 per cent, of the individuals showing the character (D+D) will appear to be just like the two parts or 50 per cent, of the individuals having the character (D+R). Therefore there will be 75 per cent, of the individuals which will show the dominant or D character, while 25 per cent, will show the re- cessive or R character. These 25 per cent, showing the R character will ever after breed true because they contain nothing but the recessive character;
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CLEMATIS INDIVISA. while of the 75 per cent, showing the dominant character, one-third or those having the pure (D+D) character will breed true in succeeding generations, while the other two-thirds having the (D+R) or hybrid character will again split in the next generation. The original idea of the operation of Mendel's law has been changed by Bate- son. His idea is that the two charac- ters of a pair are not mutually exclu- sive in the germ cell, but that there is presence or absence of the dominant character. That is, the recessive char- acter is always present, but is obscured when there is presence of the domi- nant character. On this hypothesis a yellow pea is based on green—i. e., the yellow color is superimposed upon the green. The yellow pea produces germ cells bearing two factors, one for yel- lowness (Y), and one for greenness (G). When it is self-fertilized or fer- tilized with another yellow pea, indi- viduals are produced whose germ cells have the formula YG, but the result- ing progeny always have the yellow color through the presence of the yel- low factor. In the same way the pure green pea produces germ cells carry- ing two factors—one for greenness (G), and one for absence of yellowness (Y). Out of several hundred cases of bud variation that I have collected from field, greenhouse and authentic litera- ture, the great majority of those in

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