September 25, 1895.] 



Garden and Forest. 



383 



violence of the winds. They sweep freely through the 

 open spaces, and their strength and persistence seem in- 

 creased. There is also more abruptness in local weather 

 changes and greater contrasts in temperature. The average 

 climate has not changed, but has been altered in its details. 

 Hence the greater liability to frosts and cold winds, which 

 are sometimes nearly as damaging to the fruit crop as the 

 frost. While in the region during the changeable weather 

 of May of the present year, I e.^camined some orchards after 

 the results were fully apparent. Those trees fared best on 

 the eastern slopes of hills or east of belts of wood. Where 

 the fruit was not entirely destroyed, a difference was per- 

 ceptible between the east and west sides of the same tree. 

 The cold wind which preceded the frost came from the 

 west, and when it subsided the localities most affected 

 were those which had been exposed the longest to its in- 

 fluence. In the low ground, where the cold air settled, there 

 was less difference in this respect even in sheltered areas. 



It is also evident that fields are more subject to dryness 

 in a deforested region. This is not on account of a dimin- 

 ished rainfall, but from the lack of conservation of the water 

 which falls. It runs off quickly from the fields, hurried on 

 by the the ditches and open vi'atervvays, or is more rapidly 

 dried up by the sun. The effect upon the streams is clearly 

 seen. They rise suddenly, and are full to overflowing in 

 the rainy season or after heavy showers, but are lowordry 

 at other times. Brooks that were once perennial are dry 

 for a great part of the year. The springs which feed them 

 and tend to keep them running are mostly along the bases 

 of the hills. They once provided water in the pastures 

 for the stock. Now they are more uncertain, more often 

 go entirely dry, and resort must be had to wells, which 

 go deeper into the ground. 



It is not a region that washes badly, partly from the 

 character of the soil, partly because the hillsides are kept 

 in grass when not covered with other crops, still much of 

 the soil is carried down into the valleys or hurried off in 

 the turbid waters of the swollen streams. On the hills, 

 especially the steeper ones, there is a tendency of the soil to 

 become poorer and thinner. The fact might be hard to 

 demonstrate, but it is highly probable that the region has 

 already been denuded of trees beyond what is needed for 

 the best agricultural results. With more of the hills, or 

 especially their steeper sides, left in forest, the land in the 

 valleys and on the gentler slopes would evidently be better 

 w^atered, more productive and more certain to yield a re- 

 munerative crop. 



Chicago, 111. -C. J. Hill. 



Autumnal Changes in Leaves. — I. 



THE gorgeous autumnal foliage of our temperate 

 climate appeals to us all in different ways. Poetical 

 and theological views of this phenomenon are interesting 

 and elevating, but they hardly satisfy people with scien- 

 tific curiosity. The variety of these colors is surprising if 

 we compare them, for instance, with the plates of Ridg- 

 way's Nometidalure. There are the ochre-yellow of the 

 Poplar and the closely allied, yet distinct, hues of Milk- 

 weed, Elm and White Maple ; the orange of .Sassafras and 

 Black Birch ; the crimson of the Huckleberry, Sumach and 

 Woodbine. Many plants, such as Sumach and Red Maple, 

 show beautiful combinations of yellows and reds, espe- 

 cially when these colors are relieved by more or less 

 green. In Red Maple leaves, one who is not color-blind 

 may distinguish orange, scarlet and vermilion, rose-pink, 

 lake-red, rose-red, carmine, crimson and maroon, to say 

 nothing of orange, orange-buff and ochre-yellow. Purple 

 hues are not common, but are found in some Oaks, among 

 the botanically troublesome Asters, and elsewhere. Sober 

 brown leaves show exquisite varieties of color before be- 

 coming part of mother earth. Sassafras leaves become 

 russet; raw umber is the hue of Scrub Oak, and Button- 

 wood leaves assume a rich Vandyke-brown. 



Before venturing upon some explanation of the way 

 these colors are formed, it may be well to state that 



autumn leaves are best preserved by covering them with 

 a sheet of paper, pressing w;ith a hot iron upon which 

 paraftine has been rubbed, and flattening and drying be- 

 tween papers afterward. Leaves thus prepared will retain 

 flexibility and color for years, but if pressed without paraf- 

 fine they will soon become dull and brittle. 



It will be found instructive to record the dates at vi'hich 

 various kinds of leaves change color, for comparison of 

 such dates shows, in a rough way, the relative vitality of 

 different species of plants as well as of individuals of the 

 same species. Early in July, in the vicinity of Boston, the 

 root leaves of many tender herbs and the oldest leaves of 

 Sumach begin to change. Near the end of the month many 

 leaves of Elm and Maple color and fall, but such leaves 

 are noticeably small and often deformed. By the first of 

 September a wholesale coloring has begun among Blue- 

 berry, Blackberry, Sumachs and other plants, although 

 Maples, Oaks and Poplars are not generally changed. 

 Before the end of this month Red Maples are intensely 

 colored, while Sugar Maples are not at their brightest until 

 the middle of October, in company with the Poplars. Last 

 of all come Dogwood and Scarlet Oak, alone in their glory 

 among the withered leaves of late October. 



Our autumnal colors are admitted to be much more bril- 

 liant than those of Europe, where Maples and Oaks are 

 notably fewer in number and variety. Vet the brilliancy 

 is relatively less in the old country if we compare similar- 

 trees in corresponding climates or observe American trees 

 when cultivated abroad. This is, doubtfully, attributed to 

 the "greater transparency of our atmosphere and the con- 

 sequent greater intensity of the light," but no exact obser- 

 vations upon this subject have yet been made. 



Certain it is that intensity of light has an important bear- 

 ing upon the color changes of leaves. Exposed leaves are 

 colored sooner and stronger than shaded ones, other things 

 being equal. Yet the oldest, or first exhausted, leaves of 

 a plant are the first to turn, even when more or less shaded, 

 as also occurs with stunted leaves of low vitality. Again, 

 a green leaf of Red Maple, artificially darkened when 

 about to turn, undergoes no striking color change. If a 

 part only is shaded, as by a strip of tinfoil, that part 

 remains green, while the rest becomes yellow. If part of a 

 yellow leaf is shielded from sunlight it stays yellow, while 

 the rest may turn red. The infinite diversity of color dis- 

 tribution in autumnal leaves is, I believe, largely due to 

 the varying amount of shading from sunlight which any 

 individual leaf undergoes from other leaves, etc. I have 

 found a crimson Sumach leaf crossed by an oblique yellow 

 band where a branch had pressed upon it ; also upon a 

 red leaf of Maple a distinct photograph of an overlying 

 leaf. A person's initials cut from paper and pasted upon 

 a green leaf or fruit will be sharply defined in green after 

 surrounding parts have assumed shades of red or yellow. 



Now, for an adequate explanation of these effects of 

 light, or better, light and heat, we suggest the following : 

 The leaf is a transitory structure vi'hose length of life is 

 adapted to the character of the climate, and soon grows to 

 its maximum size, which then limits its capacity for the 

 preparation of food. This assimilation, occurring in a green 

 leaf and only during sunlight, necessitates the continual 

 formation and accumulation in the leaf of certain waste 

 products, which must gradually reduce the amount of 

 assimilation itself. The leaf is choked by its own excre- 

 tions, and, becoming less able to repair its normal waste of 

 tissue, succumbs more readily to oxidation. The heat ac- 

 companying sunlight not only furthers assimilation — in fact, 

 is essential to it — but also hastens the death of the leaf by 

 accelerating the combination of oxygen with its tissues and 

 the action of acids which are formed in leaves as by-prod- 

 ucts. The effect of shading leaves from sunlight, then, is 

 simply to retard not only the normal assimilation, but also 

 the subsequent disintegration, which is indicated by color 

 changes, and is just as normal in its way. In fact, leaves 

 and bark are the excretory systems of plants, for by their 

 means useless chemical compounds are periodically re- 



