August 21, 1889.] 



Garden and Forest. 



399 



The so-called " Grit " in Apple-twigs. 



IF two Apple-twigs of equal size be cut with a budding-knife 

 one may exhibit more of that quality which is known as 

 "grit" than the other. Pear-twigs are more "gritty" than 

 Apple-branches of the same size, while Cherry-twigs have less 

 of this quality. With many horticulturists this grit, which is a 

 resistance to the knife not easily defined, has been employed 

 as a test for hardiness, and, therefore, is a quality of much in- 

 terest to the fruit-grower and nurseryman. 



In determining what the substance in question is, we may 

 note that a growing twig is not gritty, this quality being asso- 

 ciated with maturity of the stem. Thus, if we cut the tip of a 

 " water-sprout," and compare the resistance there met by the 

 knife, with that experience when a mature twig is cut, the 

 difference is very evident. Again, if a mature twig is cut 

 through its well-formed terminal bud the knife meets with 

 none of the grit, but when the twig is severed a short distance 

 below the bud the grittiness is strikingly prominent. A better 

 way to determine the location of the grit is to pass the knife 

 down lengthwise through the tip of the twig. In this way the 

 knife runs easily down for, perhaps, a half-inch or more, when 

 it strikes the point where the resistance begins. If another 

 twig of the same sort has the terminal bud stripped from it, 

 along with the bark and the thin zone of wood, there will be 

 left behind a cone of brittle pith. Instead of breaking this 

 stiff cone apply the knife, and shave the pith when the pecu- 

 liar sensation of cutting the grit will be felt. This cone of pith 

 consists of small cells, which are about as long as broad, hav- 

 ing their walls unusually thickened and the cavities closely 

 packed with starch. As the lower end of the twig is ap- 

 proached, the central portion of the pith is found to be thin- 

 walled, without starch, while the wood-zone is thicker and 

 serves to support the twig. In other words, near the dp the 

 wood-layer is so thin that the pith within it must take a very 

 prominent part in holding the bud, and, from the nature of 

 the cells, brittleness, instead of flexibility, must characterize 

 the upper two or more inches of well-matured Apple or Pear 

 twigs. 



It still remains to consider the nature of the grit of older 

 parts of the twigs as, for example, at those portions which are 

 used for cions — that is, several inches below the extremity of 

 a branch. As the bark of all Apple or Pear twigs is nearly 

 the same and offers none of that peculiar resistance to the 

 knife, it may be discarded in the present consideration. 

 The grit is, therefore, either in the wood-zone or the pith, 

 or both. It has been already stated that the pith dimin- 

 ishes in grittiness as the distance from the grit-cone near 

 the terminal bud increases, and, therefore, if there is a 

 considerable grit in an old twig it probably resides in the 

 thick ring or zone of wood. The outer portion of the pith 

 may have undergone the process of lignitication, and the thick 

 wall of the cells thus I'esulting possesses the grittiness ; but 

 there is in such twigs a system of radiating plates of pith-like 

 cells known as the medullary rays or " silver grain," composed 

 of cells in the thick walls, and in that respect agreeing with 

 the cells of the outer portion of the pith. These rays are very 

 numerous in the twigs of the Apple or Pear, and during the 

 winter are repositories for starch. Besides these plates of cells 

 stretching from the pith to the cambium, or growing layer just 

 under the bark, there are other thick-walled, square-ended 

 cells running at right angles to the " silver grain "; these, also, 

 bear starch, while the wood fibres, between them and the ducts 

 and vessels, are without this wood substance. The wood itself 

 offers more or less resistance to the knife, but it is not of that 

 kind caused by " grit." It is easy to see that making a secdon 

 lengthwise of the grain is principally a splitting process after 

 the knife is once set between the fibres, which are long and 

 slender. In cutting through the pith, in whatever direction, 

 owing to the nearly cubical shape of the cells, there can be no 

 splitting, but, instead, the knife must pass through one hard 

 lignified cell-wall only to encounter another just beyond — a 

 condition of things that produces the sensation of grittiness. 



The statement that the grit encountered in cutting twigs of 

 our common fruit-trees is due to the presence of a deposit of 

 sand in the wood is not borne out by microscopic examina- 

 tions. The nature of the tissue composing a whole or part of 

 the pith and of the "silver grain," which is only the pith 

 pressed into plates by the growing wood, does not call for any 

 such theory. 



This lignification of the pith and medullary rays and their 

 storage with starch is one of the best indications of the ma- 

 turity of the twig, and that is as far as one dares to go in his 

 deductions from these conditions. That it may be an indirect 

 index of hardiness is to be presumed, for it is undoubtedly 



true that immature twigs are not hardy, and it has been shown 

 that such do not present the quality of grittiness. 



It is also an observed fact that the lignified pith cells are the 

 only ones containing starch, and in freshly-gathered twigs in 

 midwinter these thick-walled cells invariably contain starch. 

 The grittiness, therefore, becomes a fair index of the amount 

 of starch stored as a reserve-food material in the twig, and the 

 presence of such a substance, other things remaining the 

 same, becomes a possible criterion by which to judge of the 

 adaptability of the plant to the condidons which surround it. 

 In other words, of two varieties of apples the one having the 

 greater grittiness would be the one which had stored up the 

 larger amount of reserve-food substance in the form of starch, 

 and from that fact it might be inferred that it was the healthier, 

 had better prepared itself for the winter, and, therefore, for 

 growth the succeeding spring. That it would live longer and 

 bear more fruit than its less provident neighbor must be de- 

 termined by orchard test, and not by microscopic investiga- 

 tion. The variety which matures its wood most thoroughly 

 and stores the most starch may start into vigorous growth 

 too early in the spring and be injured, perhaps, seriously 

 thereby. Grittiness is, therefore, a good sign, but it does not 

 become a perfect test for hardiness. 



Rutgers College, New Brunswick, N. J. ByrOH L>. Halsteacl. 



Entomological. 

 The Asparagus Beetle. 



'T^HIS summer. Asparagus growers in eastern Massachusetts 

 -'- have been making complaints of injuries to their plants 

 caused by the Asparagus beetle (Cr/oci^r/j- ^j/izraof), generally 

 indefinitely spoken of as a "fly," "slug," or " bug" by those 

 making its acquaintance for the first time. In some gardens the 

 plants have been completely defoliated, leaving only the bare, 

 dry stalks and branches, much to the injury of the vitality of 

 the roots and of the value of the next season's crop. 



Remedies do not seein to have been generally known or used, 

 and in some cases it is to be feared that more injury lias been 

 done to the plants in efforts to exterminate the pest than if they 

 had been left undisturbed. 



Late in July, upon finding the Asparagus badly eaten by the 

 insects, some, gardeners have cut down every living shoot that 

 was above ground, and kept all cut back for some time in the 

 hope of "starving out" the insect. By cutting away the tops 

 so late in the season much injury is done to the roots, and, as 

 many of the larvje will have reached full growth, they are not 

 starved but merely enter the ground or find some other suit- 

 able place to pupate or prepare a new lot of beetles to deposit 

 eggs on fresh shoots when they appear. The first lot of beetles 

 begin to deposit their eggs in the spring, at a time when the 

 Asparagus is cut daily for market and table use, and if grow- 

 ers were careful to keep down all seedling or stray shoots, and 

 destroy all those that have become wild, during this period, it 

 would help to starve out the first brood at least, because the 

 beetles would be forced to deposit their eggs on the shoots 

 that were to be cut for use, and they would thus be destroyed 

 before hatching out. If this practice is followed by all the 

 growers in any district it will have the effect of materially less- 

 ening the numbers of the pests, so that later in the season 

 they will not be so troublesome. 



As soon as the young larvit appear, after the marketing 

 season is over and the Asparagus is allowed to grow naturally, 

 the use of insecticides should be resorted to, and repeated 

 during the summer whenever the insects recur in any number. 



Fresh slacked lime dusted on the plants is found by many 

 to be very effective, and one of the cheapest and most easily 

 applied of remedies. It is efficient only against the larvre, the 

 beetles being unaffected by it. Arsenical poisons, such as 

 Paris green or London purple, used in the same manner and 

 proportions as for the potato beetle, are as effective against 

 the Asparagus insect as they are in preserving the potatoes. 



The Asparagus beetle is an importation from Europe, and 

 its first appearance in this country was on Long Island, New 

 York, thirty years ago. It soon became very destructive to 

 the large plantations on the island, and a few years later it was 

 doing much damage in New Jersey. Since then it has slowly 

 spread over a large territory, estimated by some to be less 

 than at the rate of twenty miles a year. The beetle averages 

 about one-fourth of an inch long, and has the head, attennae, 

 legs and under side of the body black. The thorax is red witli 

 two long black spots on the top. The wing-covers are black 

 with three large lemon-colored spots on each. The middle and 

 the anterior spots are often joined, and appear as one irregu- 

 larly-shaped long spot, and then the black has very much the 



