Summary

Walnuts husked soon after harvest, before they are completely air-dried, and stored in moist peat at 1 to 3° C. for five to six months have their dormancy broken and remain viable for at least three months thereafter. This treatment is effective for all ten species tested. It is probably effective for all species of Juglans. This method of handling the nuts has the advantage over outdoor stratifying or autumn planting which often result in much damage or loss of nuts from the activities of rodents.

Table 1. Germination of nuts of Juglans spp. after stratifying in
peat over winter, at 1-3°C.

Kind	Source	Date entered in storage	Planted in soil in greenhouse April 15	Planted in field April 24	Planted in sphagnum June 2
		Per cent germination
nigra	(Cornell) Ithaca, N. Y.	Oct. 1	70	80	68
nigra	(Cayuga) Ithaca, N. Y.	Oct. 1	100	—	80
cinerea	—Ithaca, N. Y.	Oct. 1	60	44	8
regia	(Sorrentina) Chico, Calif.	Nov. 9	66	48	8
regia	(Franquette) Chico, Calif.	Nov. 9	80	36	—
regia	—Chico, Calif.	Nov. 9	75	46	—
Sieboldiana	—Ithaca, N. Y.	Oct. 1	100	40	—
honorei	—Chico, Calif.	Dec. 18	60	55	46
pyriformis	—Riverside, Calif.	Nov. 9	10	54	31
rupestris	—Alpine, Texas	Oct. 1	40	83	50
major	—Riverside, Calif.	Nov. 9	90	92	66
californica	—Pomona, Calif.	Nov. 9	62	84	91
californica	quercina —Chico, Calif.	Dec. 18	—	18	25
hindsii	—Riverside, Calif.	Nov. 9	50	56	52

References—

1. Brown, Babette I. Injurious Influence of Bark of Black Walnut Roots on Seedlings of Tomato and Alfalfa. Northern Nut Growers Association, 1942: 97-101. 1943.

2. Barton, Lela V. Seedling Production in Carya ovata. Juglans cinerea and Juglans nigra. Contr. Boyce Thompson Inst. 8: (1) 1-5. 1936

A Key to Some Seedlings of Walnuts

W. C. Muenscher and Babette I. Brown

Cornell University, Ithaca, N. Y.

While working with the seedlings of several species of walnuts certain diagnostic characters, by which the common species can be separated, became evident. These characters have been used to make a key to seedlings from one to three months of age. This key has been found helpful to us and it is here presented in the hope that it may prove useful to others who need to handle and determine walnuts in the seedling stage.

The key has two main divisions based upon the types of leaves on the main axis. The first division includes three species, Juglans sieboldiana, Japanese butternut, J. cinerea, American butternut, and J. regia, Persian or English walnut, all of which have only compound green leaves. In addition, one or more pairs of minute simple scales or buds occur on the lower part of the stem but above the cotyledons. The second main division includes species in which the seedlings have several simple, alternate, scale-like leaves followed successively by serrate, lobed and finally compound leaves forming a gradual series. This group includes Juglans rupestris, Texas black walnut, J. nigra, eastern black walnut, J. honorei, Ecuador walnut, J. pyriformis, Mexican walnut, J. major, Arizona black walnut, J. californica, California black walnut, and J. hindsii, Hind's black walnut.

It is important that the leaves on the primary axis arising from the plumule are examined. If the primary axis is injured secondary shoots may arise from the axils of the cotyledons. These may develop various types of leaves not necessarily like those of the primary axis. The key is based upon seedlings grown in the field and in the greenhouse at Ithaca, New York.

A Key to seedlings of some species of Juglans
1. Leaves on the primary axis all compound; 1 to 4 pairs of opposite or
subopposite reduced scales or buds sometimes present on the lower
axis but above the cotyledons.
2. Scales or buds wanting between the lowest compound leaves and the
leaves and the cotyledons J. sieboldiana
2. Scales or buds in pairs on 1 to 4 nodes below the compound leaves.
3. Stem with 1 pair of opposite scales or buds near the base; leaflets
hairy, serrate J. cinerea
3. Stem with 2 to 4 pairs of opposite scales or buds below the compound
leaves; leaflets glabrous, entire or denticulate J. regia
1. Leaves on the primary axis alternate, forming a gradual series from
simple, entire scales to compound leaves; the lower 3 to 8 leaves simple.
4. Lateral veins of leaflets all or mostly all terminating in the notches
between marginal teeth J. rupestris
4. Lateral veins of leaflets or their main branches all or mostly all
terminating in the apex of marginal teeth.
5. Midrib of leaflets glandular hairy.
6. Glandular hairs on midrib of young leaflets interspersed with
stellate clusters of gray glandless hairs; lateral leaflets ovate
to broadly lanceolate, rugose J. nigra
6. Glandular hairs on midrib of young leaflets interspersed with
sessile, usually yellow glands; lateral leaflets lanceolate, not
rugose J. honorei
5. Midrib of leaflets glabrous or nearly so, sometimes with scattered,
sessile glands.
7. Leaflets lanceolate, with acuminate apex; rhachis glabrous.
8. Leaflets widest near middle; vein-islets prominently
raised; free ends of veins wanting or if present distinct
to the apex and mostly unbranched J. pyriformis
8. Leaflets mostly widest below the middle; vein-islets not
prominently raised; free ends of veins slender, terminating
in indistinct branches J. major
7. Leaflets ovate or nearly so, with obtuse or acute apex;
rhachis somewhat pubescent.
9. Petioles of the 3 lower compound leaves less than 1 cm.
long; leaves crowded on a short axis J. californica
9. Petioles of the lower compound leaves from 1+ to 3 cm.
long; leaves more distant on an elongated axis J. hindsii

Further Tests with Black Walnut Varieties

L. H. MacDaniels and J. E. Wilde, Cornell University

In 1937 the Northern Nut Growers Association committee on varieties and judging standards proposed a tentative schedule for the judging and evaluation of black walnut varieties(1). It was pointed out at that time that for one reason or another none of the schedules which had been used in judging walnuts were satisfactory and usable in giving an accurate estimate of the cracking quality and value of a variety. It was recognized also that the schedule proposed was only tentative and that it would need to be modified in the light of future testing and experience. In 1939 the question was again considered(2) and on the basis of tests which had been made, changes were proposed which would make the schedule more realistic. Since then many tests have been made using the modified schedule. The purpose of this paper [A] is to give the data secured in these tests and to consider again the value of the schedule and possibilities of improvement.

Recently a number of papers have been published dealing with the evaluation of black walnut varieties. In 1941 Kline and Chase(3) compiled the available published data and additional tests made by the Tennessee Valley Authority on nut weight and kernel percentage of black walnut selections. Two hundred and twelve clones and 335 tests are reported. As would be expected the samples of the same variety from different localities show variation in weight per nut and in total per cent kernel. For example, in 12 samples of the variety Ohio the weight per nut varies from 14.8 grams to 18.7 and the per cent kernel from 16.6 to 32.9. Twenty-one tests of Thomas show variations in single nut weight from 16.7 to 25.0 grams and in per cent kernel from 19.0 to 30.0. In general the samples grown in the north were made up of smaller nuts with less per cent kernel, indicating that the varieties were not suited to that latitude.

In 1942 Kline(4) worked out a somewhat technical method of evaluating walnut varieties on the basis of cash return per hour of labor spent in cracking with a hand operated cracker. A formula is proposed in which the variables of price and other factors may be substituted. The approach is on a commercial basis and the method is not intended for use in evaluating small samples. The paper represents many tests and establishes or affirms by statistically treated data several points of general interest in walnut testing, namely, (1) that a 25 nut sample is large enough to show varietal or other differences of a gram in total weight or 1 per cent of kernel weight, (2) that unless extreme accuracy is desired, moisture content may be ignored in making tests of 25 nut samples if the nuts have been hulled and air dried for about two months and (3) that the mean weight per nut and per cent kernel of nuts from the same tree may vary appreciably from year to year, for example a variation of 4.9 grams per nut and 3.3 per cent in kernel weight is reported for Snyder. Such variation is recognized and emphasizes the necessity of testing a variety in any locality for a number of years if correct valuation is to be made.

In Kline's paper earnings per hour for fifteen black walnut selections are given showing a maximum of $0.279 for the variety Norris, $0.245 for Ohio down to $0.12 for an unnamed seedling.

Lounsberry(5) published kernel cavity measurements for 64 clonal selections and related these to kernel weight per nut. Measurements of the thickness of the partition separating the halves of the kernel are also given. He does not relate these characters to scoring or cracking quality.

The purpose of the scoring system under discussion in this paper is to provide a realistic method of judging the relative merit of different clones of black walnuts that can be used mostly by members of the Northern Nut Growers Association or others having some skill in cracking technique. At the present time the Association has little reliable information either as to the performance of different varieties under different conditions in any one locality, from year to year on the same tree, or the suitability of any one variety growing in far different parts of the United States. It is important that such information be available and a workable basis of evaluation would be of the greatest value in obtaining it. Much of our information at the present time is from the many tests made by N. F. Drake(6, 7, 8) which are of great value in rating varieties. His schedule is an improvement over any previously proposed but fails to provide standard sampling and cracking procedure and includes the items of flavor and color which are in no way objective characters. The use of a point score based on the concept of a "perfect nut" is cumbersome and considered undesirable by the committee.

It is recognized that the value of a variety depends also upon the bearing habit of the tree, the nature of the husk, disease resistance and other characters.

It has been five years since the present schedule was proposed and enough tests have been made to give a basis for judgment as to the merits and weaknesses of the schedule. As stated in the original committee report it is generally agreed that the best measure of the value of a nut of any clone is the amount of usable or marketable kernels that can be obtained from a given weight of shucked nuts with the least labor. The characteristics of the nuts that contribute to this value are recognized as follows:

1. The size of the individual nut.
2. The per cent of kernel of total sample weight recovered without recracking
and without the use of a pick.
3. The total per cent of kernel of total weight of sample.
4. The number of quarters.
5. The plumpness of the kernels.
6. The number of empty nuts or nuts with shrivelled kernels in the sample.

Flavor and color may be important but are so dependent upon personal preference and on the treatment of the samples before testing that they cannot be rated numerically.

In considering the value of any schedule the following questions are pertinent:

1. Is it possible for one operator testing one lot of nuts to obtain the same score with replicate random samples?

2. Is it possible for different operators to obtain approximately the same score on replicate samples?

3. Does the score give an accurate evaluation of the variation of a variety from year to year in one locality or in the same year in different localities? The latter is very important in determining the regions to which the variety is best adapted and the performance of the variety in any one locality.

4. What are the causes of variation in the scores obtained? Which of these reflect the inherent worth of the sample and which are related to technique, personal equation and methods of handling the sample?

5. What changes may be made in the schedule to weight the various factors to give a more realistic score of what changes in procedure will make the schedule more realistic?

Table 1 gives data on replicate samples tested by the same operator. In the samples of Spear, numbers 1-6 the variation is as follows: weight of single nut 1.3 grams, per cent kernel first crack 2.9, total per cent kernel 2.6, number of quarters 3, penalties 4.5 points, score 9.2 points. In scores figured without penalty the variation is 5.4 points. Sample No. 7 was cracked November 4 before the nuts were dry and hence is not comparable with others.

Analysis of these differences indicates that the variation in nut weight is closely related to the number of shrunken and empty nuts in the sample. This is a difficult factor to evaluate in a practical way. At the time of the 1939 report it was suggested that the score should be figured on the basis of filled nuts. This cannot be arranged easily in testing because if the operator cracks the nuts before weighing there is almost sure to be loss of fragments of shell. Trying to correct the original weight in any way is necessarily inaccurate. Deciding whether or not the kernel of a nut is sufficiently shrivelled to deserve a penalty is a matter of judgment which is a personal matter.

The variation in per cent kernel first crack and total per cent kernel probably represents fairly the difference in the samples. The total per cent is a wholly objective value and varies practically as much as the per cent first crack. Uniformity in the number of quarters is striking. This large number is undoubtedly related to the fact that many of the kernels were shrunken enough to be penalized and others were perhaps shrunken enough so that they did not tightly fill the shell cavity. In general it may be said that the more tightly the kernels fill the shell the more difficult it is to extract large pieces. Thus having the kernels a little shrunken but not enough to seriously reduce their weight favors a higher score. Of course, in some varieties the kernels may he plump and still not fill the shell tight enough to make cracking difficult. This is a desirable condition.

Variability in penalties is more important (i. e. 4.5 points) than any other factor in influencing the final score. Without the penalties the scores of samples 1 to 6 would be 87.5, 84.0, 83.6, 83.7, 82.1 and 82.8 respectively which is fairly uniform. Statistically the presence of empty or shrivelled nuts in a lot from which samples are taken increases the number required to make a satisfactory sample by greatly increasing the individual variation of the single nut.