AURICULA 



AUTUMN-GARDENING 



431 



greenhouse for the winter. All decaying leaves should 

 be carefully removed, and but little water will be 

 required during the dull winter months. Toward the 

 end of February the plants will show signs of flowering, 

 when they should be given a top-dressing of pulverized 

 sheep-manure and placed in a light, airy position, in a 

 temperature of 55. The flowering season lasts about 

 two months, after which the plants should receive 

 their annual potting. All diseased or decayed roots 

 should be cut away, and most of the old soil carefully 

 removed. The propagation of very choice varieties by 

 offsets or division is best done at this time. The pots 

 used in potting should be 

 well drained, and no larger 

 than will just accommodate 

 the plants. The soil best 

 suited is the same as before 

 recommended. After pot- 

 ting, they may be placed 

 in their summer quarters. 

 Offsets should be inserted 

 around the edge of 4-inch 

 pots, using very sandy soil, 

 and kept in a moist, shaded 

 position until rooted. By 

 annually repotting and giv- 

 ing a little extra care dur- 

 ing the summer months, a 

 batch of show auriculas will 

 return very satisfactory re- 

 sults, and may be kept in 

 a good, healthy condition 

 for several years. 



EDWARD J. CANNING. 



440. Auricula. ( X H) 



AUTUMN COLORS, 

 PHYSIOLOGY OF. When 

 the conditions in almost 

 any locality are favorable 

 for the rapid growth of plants, the prevailing color of the 

 vegetation is green. The leaf-green, or chlorophyll, is 

 a conspicuous part of vegetative organs. Green is 

 normal, so that one does not regard a green plant as 

 "colored." It is true that in some species of plants, 

 chlorophyll is partially or completely veiled by the 

 presence of other pigments, and in the blossoms it may 



E raetically fail; but in the latter case the life of the 

 rilliant structures is fleeting, and green is promptly 

 predominant. "Color" is more or less restricted to 

 blossoms, to particular species, or to seasons. The great 

 seasonal change is here the center of interest. 



In the autumn the vegetation of the usual temperate 

 landscape loses gradually its distinctive green, while 

 striking yellows and reds are substituted. With favor- 

 able conditions, the climax of this transformation is 

 such a riot of color as is not seen at any other time. It 

 is noteworthy that this change is an immediate fore- 

 runner of leaf-fall and death. The vegetation that is 

 suddenly cut off by severe frost seldom exhibits true 

 autumnal colors, but instead the dry brown or black- 

 ened effects of rapid death, characteristic of any sea- 

 son. On the other hand, autumn tints of leaves may 

 appear in the summer, as when limbs of the hard maple 

 or peach are ringed. This suggests that the produc- 

 tion of color is susceptible of experimental study. On 

 the whole, the layman may regard the autumn colors 

 as a necessity to the wholesome rounding out, and a 

 fitting terminus, of a season of usefulness. Coloration 

 is, however, an evidence of fundamental physiological 

 changes; and it is appropriate to ask regarding the 

 climatic or other conditions which bring this about, as 

 well as concerning the nature of these internal changes 

 which also make for the development of color in the 

 autumn. 



For the most part, the autumn leaf -colors fall into 

 two groups yellows and reds. These colors are pro- 



duced by two groups of pigments essentially different in 

 chemical and physical properties; yet these pigments 

 are frequently blended in the same leaf, yielding such 

 gorgeous effects as may be seen in the sumach. 



The yellow pigment (more correctly pigments) of 

 leaves occurs in the chlorophyll bodies of the cell. It is 

 present in conjunction with the leaf-green in the 

 healthy leaf, but not infrequently it seems to increase 

 in quantity as the chlorophyll disappears. It belongs to 

 a group of substances often called xanthophylls. These 

 are carotin-like compounds, that is, related to carotin, 

 the orange or orange-red pigment of the carrot root. 

 Carotin-like bodies are widely distributed in plants and 

 are also responsible for the yellow, orange, and orange- 

 red colors of a large number of blossoms. These pig- 

 ments do not occur in solution in the cell-sap, but may 

 be present either in the healthy chlorophyll bodies 

 (plastids) or outside of them. In the latter case, they 

 form crystals, or are in solution in droplets of fatty 

 oils. Carotin-like compounds are more permanent than 

 chlorophyll, so that any green plant may exhibit a yel- 

 lowish color upon the gradual disappearance of the 

 chlorophyll. 



The red pigments of autumn leaves are cell-sap colors, 

 substances soluble in the aqueous solution constituting 

 plant juices. They are supposed to be tannoid com- 

 pounds, and are generally referred to as anthocyanin. 

 The pigments of red beets and dark grapes are similar 

 compounds. It is significant that those plants exhibit- 

 ing conspicuous red coloration in the autumn are 

 usually those which give some indication of red during 

 the growing season, as in the possession of red petioles 

 or twigs; and, more especially, they are those in which 

 red is more or less conspicuous as the buds open and the 

 leaves unfold in the spring. The attractive tints of 

 unfolding hard maple buds are therefore an indication 

 that the maple has the capacity to develop a coloration 

 of the cell-sap in the autumn. Some plants develop no 

 anthocyanin under normal conditions of growth. 



It is then evident that the yellow colors of autumn 

 leaves may be due to both a greater visibility of the 

 yellow in the chlorophyll body when the chlorophyll 

 disappears, and also to actual increased development 

 of carotin-like compounds. The reds and purples in 

 autumn leaves are a result of the formation or increased 

 formation of tannoid compounds. The question then 

 is: What are the conditions which make the autumn 

 season particularly favorable for the development of 

 these substances? 



Some careful studies have been made that bear 

 upon this question. It appears that the production of 

 autumnal reds in many species is related to the sugar- 

 content, and color may be induced or heightened in the 

 shoots of many plants by growing them for a time in 

 strong solutions. Moreover, cold weather has been 

 found to be generally favorable to the accumulation of 

 sugar in the tissues. Observation indicates that after a 

 season favorable for growth, a cold, protracted autumn 

 results in exquisite autumn coloration. It is certain 

 that nothing is more disastrous to brilliance of color 

 than severe early frosts. In addition to enhancing 

 pigmentation, sugar-content seems to be most impor- 

 tant as one factor in cold-resistance. It requires a very 

 light frost in the late summer to kill outright the leaves 

 and young shoots of many trees, but the same shoots 

 may be unaffected by an equal degree of cold when the 

 conditions have been such as to bring about the normal 

 autumn coloration. g M DUGGAR. 



AUTUMN-GARDENING. There is wealth of 

 material for spring -and summer -gardening; but to 

 secure good garden effects in autumn requires mostly 

 other material and a different intellectual conception 

 of the problem. The common problems of the gardener 

 in autumn grow out of two facts: First, the frost kills 

 tender plants sooner than he desires; therefore he tries 



