December i6, 1891.] 



Garden and Forest. 



59i 



an event of extremely rare occurrence. Our great southern 

 evergreen Magnolia is frequently planted in gardens here, and 

 a large number of them were noticed as either dead or very 

 much injured. In fact, the straggling appearance of the best 

 of the survivors showed that the trees are here liable to more 

 or less injury every winter. Some were bearing a good num- 

 ber of their beautiful blossoms, for the sake of which no lover 

 of flowers could resist having these trees in his garden so long 

 as there was a chance of their living at all. The trees do not 

 attain large size here, but grafted plants may be expected to 

 bloom when only a few feet high. 



At this time (July 17th to 20th) some large trees of Catalpa 

 bignonioides were in full flower, or nearly so, and were ap- 

 parently quite as much at home and as vigorous as in our own 

 gardens. Specimens of a fastigiate form of our common Lo- 

 cust were noted here and there, the shape being so much like 

 that of the Lombardy Poplar that unless closely observed this 

 form of the Locust might be mistaken for it. The variation of 

 the Locust known as Robinia Pseudacacia, monophylla, is oc- 

 casionally seen in the streets and yards here, presenting such 

 a distinct aspect that many people, not familiar with the nu- 

 merous forms which the species has developed under cultiva- 

 tion, might readily mistake it for something new. This form 

 often has only one, and usually not more than three large leaflets 

 to each leaf. It must be propagated by grafting, layering, from 

 pieces of roots, or other modes of division, in order to be true, 

 as seeds would probably simply produce the common type, 

 except in a very few cases. Although it is one of our own 

 native trees, the Locust in Europe has a much better chance to 

 develop into good specimen trees when planted singly, because 

 it is, apparently, not liable to injury from such destructive 

 borers as we have to guard against. 



Some fine specimens of our Black Walnut {Juglans nigra) 

 are to be seen in Geneva, and a tree of the Striped Maple {Acer 

 Pennsylvanicum) was noted as having a spread of branches of 

 about thirty feet, and with an equal height. It was grafted on 

 the Sycamore Maple {A. Pseudoplatatttcs), and the stem was 

 ten inches in diameter, being smaller than its dark shaggy- 

 barked stock. 



A peculiar feature of some of the streets and quays where 

 shade and, at the same time, an unobstructed view of moun- 

 tains or lake from houses or hotels is desired, is the rows of 

 trees cut back so that they have a low, flat, or umbrella-shaped 

 top, while the lower branches are trimmed high enough to 

 allow of all ordinary passing beneath. The species most sub- 

 jected to this treatment, and one which apparently bears it 

 very well, is the variety of the Oriental Plane-tree known in 

 nurseries as Platanus acerifolia. This form is very much 

 planted in many Continental cities, and, altogether, as a street 

 tree it compared very favorably with any other kind which 

 came under my notice. The trees rarely showed any evidence 

 of disease. Such a serious blight as the fungus (Gliosporium 

 nervisequum), which destroys the growing tips of, and is so in- 

 jurious to, the Planes in many parts of America, is, seemingly, 

 unknown among the allied trees in Europe ; or, at least, it does 

 not appear to a noticeable extent. The foliage, too, is usually 

 remarkably exempt from depredations by insects. The trunk 

 is not liable to attack by borers, and although the peculiar 

 blotched appearance of the trunk is objected to by some peo- 

 ple, it has the merit of being smooth and looking as if scraped 

 — facts which are greatly to its advantage in localities where a 

 mania prevails for having the trunks of rough-barked trees 

 smoothly planed or shaved. 



The trunks of the trees in the streets of Geneva rarely show 

 any evidence of mechanical injury. Stems of the smaller 

 trees are very simply and effectively protected by having 

 shoots or branches of Locust or Buckthorn placed around 

 them and held in position by two or three bands of light iron 

 wire. 



Three species of European Lindens, or Lime-trees, were 

 particularly noticed in the streets and squares. One of these, 

 known as Tilia platyphylla, had been out of blossom for some 

 time and the fruit had already attained almost full size. The 

 second species, perhaps, should be known as T. ulmifolia, al- 

 though it is most commonly called T. parvifolia, and, among 

 other synonyms, frequently passes as T. Europcea. This was 

 in full bloom and attracted many insects. The apparent rea- 

 son of the name ulmifolia, or " Elm-leaved," was quite notice- 

 able in some very large trees here, because the foliage and 

 even the outline of the tree gave much the same effect as that 

 of the common European Elm {Ulmus campestris), the leaves 

 of the Linden not being much larger. The foliage of this and 

 the preceding species was sometimes greatly injured by the 

 attacks of aphides and red mites. The third Linden noticed 

 was T. petiolaris, a species differing from the others in its dis- 



tinct habit, its long, petioled leaves with white under-surfaces, 

 and especially in the fact that it had not yet opened any of its 

 flower-buds. 



Other Lindens may be referred to later, but attention is 

 called to those mentioned because here were three species 

 flowering in such succession as to furnish a rich and continu- 

 ous harvest of nectar for bees during a period of six weeks or 

 more — a fact, perhaps, well worth considering when planting 

 trees in a country where apiculture is much followed and 

 where the honey made from the flowers of the Linden is espe- 

 cially prized. 



Arnold Arboretum. J . G. Jack. 



The Colors of Leaves. 



T N my article on the colors of flowers the conclusion arrived 

 ■*- at is that, next to green, white is the primary color, and 

 the color from which all other colors are derived. 



Another question has suggested itself to my mind since 

 writing the former paper — a question entirely germane to the 

 subject — namely, Is the green color of leaves and vegetation 

 generally the original, primordial color, or is it secondary ? 



The method to be employed in answering this is somewhat 

 different from that used in regard to flowers. We do not find 

 any leaves with a different color at the base, as is common in 

 the case of flowers as, for instance, white ; indeed, rarely is a 

 leaf any other color than green when it is found on a stem 

 growing spontaneously in its native habitat, except in the case 

 of vigorous saplings, where the old trees have been felled. On 

 these not uncommonly the leaves are reddish or purple. In 

 cultivated plants, also, we have copper-leaved Beeches, Ma- 

 ples, etc., and some herbaceous plants with reddish foliage. 

 The colors of autumn leaves are not referred to for the rea- 

 son that they are clearly secondary. One other color occurs 

 more rarely still, and that is white. Dr. E. Lewis Sturtevant 

 pointed out to me at Nonquitt, Massachusetts, growing spon- 

 taneously on a border of a marsh, a grass called Phalaris 

 arundinacea, vax ■. picta, which had longitudinal stripes of white 

 running parallel with the green, and similar in appearance to 

 the garden Striped Grass. In my former article I referred to 

 the fact that sepals and involucres sometimes become white, 

 as, also, some of the smaller upper leaves and upper portion 

 of the stem in Daucus Carota ; but while native plants with 

 white leaves are rare, there are frequent examples of white in 

 cultivated foliage plants, so called. Among the latter is a vari- 

 ety of the Ash-leaved Maple, which has every leaf bordered 

 with white, presenting to the beholder an odd and fantastic 

 appearance, also a shrubby Althea, similarly marked ; also 

 Euphorbia, Ivy Geranium, Coleus, Funkia, Century-plant, etc., 

 are bordered, striped, or splashed with white. The inner 

 leaves of Cabbage are white, and Celery blanches white. This 

 etiolated condition of the foliage is regarded by gardeners to 

 be the result of disease or unhealthiness, and, therefore, not 

 desirable, but yet is tolerated on account of the striking, if not 

 wholly pleasing, effect produced by the unusual contrast of 

 colors. From the foregoing we get pretty strong hints that 

 green is derived from white. There remains one more clue. 

 Every botanist knows that the seed contains a miniature and 

 rudimentary plant ; that generally the most prominent parts 

 of this seed are the cotyledons, or seed-leaves, and these are, 

 of course, the first leaves of every species of plants. Now, if 

 we ascertain the color of these seed-leaves we find the orig- 

 inal color of all leaves. This color is uniformly white. 



Take, as a few familiar illustrations, the seeds of apple, 

 pear, peach, grape, tomato, cranberry, bean, corn, hickory, 

 chestnut, oak, filbert or almond. Of course we do not re- 

 fer to the colored integuments of the seed, which, as in the 

 case of garden beans, may be white, red, yellow, blue, black, 

 or mixed colors, but to the kernel, or meat. There are a 

 very few instances only where the green color of the plant 

 has impressed, somewhat, that characteristic upon the seed, 

 as in peas, nasturtiums and maples, which present a pale 

 green color in the pod, or shell. In some instances, these 

 cotyledons appear above the surface of the ground changing 

 from white to green ; while in others they remain below, 

 where planted, only to nourish the growing stem and succeed- 

 ing leaves. 



Nature, which has all colors at her disposal, has selected 

 green as being the best adapted for the vegetal function ; 

 that is, green is "the survival of the fittest" for that purpose. 

 For the promotion of the fructifying function insect agency is 

 important, both in fertilization and cross-fertilization. Insects 

 are guided, doubtless, by bright colors, as well as by scent, 

 and that the colors may be attractive they must be different 

 in hue from the general foliage and in strong contrast thereto ; 



