132 BOTANY: A. B. STOUT 
A better understanding of the nature of the tissue complex in certain bud 
variations has been gained from the knowledge of chimeral structures. When 
a somewhat permanent somatic variation occurs in only a part of the cells or 
in a single cell of a growing point such a cell or cells may be so situated that the 
cell progeny form permanent layers giving periclinal chimeras, or sectors giv^ 
ing sectorial chimeras. There is also the possibility that irregular processes 
of development or the occurrence of repeated somatic variations during or- 
ganogenesis may give complex mixtures or hyper chimeras. Anatomical proof 
of the existence of such chimeras was first presented by Baur (1909) and the 
experimental production or interspecific chimeras was demonstrated by 
Winkler (1907). 
Numerous cases of albomarginate variegation are apparently of the peri- 
clinal type. The originial variation in such cases is partial, affecting a part 
of a growing point only. Further changes, such as return to pure green 
branches, may involve simply a mechanical readjustment of the elements pres- 
ent in the growing points (Stout 1913). Chimeral association of cells differing 
sporadically but more or less permanently in fundamental hereditary qualities 
undoubtedly accounts for much of the irregularity seen in the seed progeny of 
bud sports. Various types of chimeras especially periclinal and hyperchimeras, 
without doubt grade imperceptibly into cases of ordinary differentiation 
in which the cells quite alike in fundamental hereditary qualities become 
differentiated through their relations as parts of the whole. 
In general, our available knowledge regarding somatic variations indicates 
that they show a wide range of variability suggesting that hereditary elements 
or units are themselves variable even in a series of somatic cell-divisions. The 
evidence is especially convincing, for here there is a most direct lineage of cell 
elements far more simple than that obtained in reproduction by seed progeny 
which involves the intricacies of periodic reduction and fertilization. Un- 
questionably the phenomena of bud variation involve the most fundamental 
questions of heredity. The intensive study of bud variants in successive gen- 
erations propagated vegetatively should reveal definite facts regarding the 
nature, frequency, and permanence of spontaneous changes. Since 1911 the 
writer has studied bud variations in a variety of the variegated Coleus with 
these aims in mind. Over 1211 pedigreed plants have been grown, com- 
prising fourteen generations (two each year), all propagated by cuttings, the 
first of which were taken from two similar sister plants. 
The frequent variations that have appeared range from sudden changes to 
gradual fluctuations, and these may first become evident in a part (even 
a small area) or the whole of either a leaf, a bud, or a plant. The characters 
studied have been those of leaf form and leaf coloration. 
The somatic variations found in leaf coloration involved (1) gain or loss, 
increase and decrease of green and yellow, (2) reversals of the relative positions 
of the green and yellow in leaves, (3) increase and decrease of red pigmenta- 
tion, and (4) changes in the distribution of the red pigmentation, especially that 
