Heredity Studies in the Morning-Glory g 



Flowering. None of the others were ragged. The flowers were white, 

 and, altho the rays were plain white while the plant was growing in the 

 weak light of the greenhouse during the winter, later in the season a 

 lavender spot developed on each. This spot appeared also in the progeny. 



This plant, no. 5-2, was used in six crosses, with plants of various colors. 

 The raggedness appeared in the Fi colored hybrids. Only 12 plants came 

 to bloom in these six pedigrees. Of these, 7 were ragged and 5 were smooth. 

 The indication is, then, that the plant no. 5-2 was simplex for the gene 

 causing this character, and that the character is a dominant one. The 

 data for F2 and F3 generations regarding this character are very meager, 

 but the indication again is that the smooth or recessive plants breed true 

 to lack of the character. 



This character was transferred from the original white plant to various 

 plants of the color types by crossing. 



PIGMENT COLORS IN PLANTS 



There are two classes of coloring substances in plants: (i) organized 

 color principles, which are characterized by being an organic part of the 

 plastid body and are always associated with specialized protoplasmic 

 bodies, the chromoplastids ; and (2) unorganized color principles, which 

 are not a fundamental or organic part of the plastids, but are pigments 

 dissolved in the cell sap and seated in the vacuoles of the cells. In flowers 

 the latter are almost always confined to the epidermal cells, but when 

 found in leaves, fruits, and other organs they are situated as often as not 

 in deeper-lying tissues. 



According to the modem theory of the formation of these cell-sap 

 pigments, they are the result of enzymes in the nature of oxidases which 

 act upon certain substances in the cells that are capable of oxidation, 

 thereby producing pigments. The oxidase is supposed to be of a dual 

 nature and to consist of two constituents, a peroxidase and a peroxide. 

 The peroxide functions as an activator to the peroxidase in the sense that 

 it supplies the latter with oxygen which may then be transferred to an 

 oxidizable body. When all three substances are present, the peroxide, 

 the peroxidase, and the oxidizable body, oxidation takes place and pig- 

 ment is formed which gives color to the organ. 



Tests by various workers on many different species of plants show that 

 the distribution of oxidases coincides with that of the anthocyanic pig- 

 ments, and it has been pointed out by Miss Wheldale (1910, 1911)^ and 

 by Clark (19 n) that peroxidase is more widely distributed than the 

 organic peroxide that activates it. 



I Dates in parenthesis rel[?r tg Ref«rincei cited, page 38. 



12§ 



