Material and apparatus. Branches of several of the commercial groups of plums, bearing fruit buds and branch buds; razor, dissecting lens.

The genus Prunus includes the plum and the cherry, and is widely distributed. These species, cultivated for their edible fruit, are found only in the temperate zone of the northern hemisphere. The flowers, twigs, and buds in each group will be found to differ, as may be verified after studying them.

Plums

The plums are divided into several important, more or less distinct, commercial groups, with many hybrids between the groups. The following groups are a few that admit of careful study. 1. Prunus domestica includes the following varieties: Bavay, Lombard, Gold Drop, Arch Duke, Diamond, Monarch, Italian Prune, Yellow Gage, and several others.

a. Secure branches, including both fruit buds and branch buds, of one of the above varieties. Draw a twig, natural size, and at least four inches in length. Measure the distance between the internodes and count the number of buds in a cycle. Describe the color of the bark. Are the lenticels numerous or few? Describe.

Pig. 11. Branch buds and fruit buds of plum. Note the clusters of buds that are borne on the short spur.

b. Draw a longitudinal and a cross section of both a flower bud and a branch bud. Describe the differences. How many ovules do you find in a bud? Is the number constant or variable? Discuss. Does the fruit bud differ from the branch bud in position on the stem? Discuss.

c. Make a drawing, at least one inch in length, of a branch bud and a flower bud. Remove several of the bud scales, and make a drawing of a scale from both the branch bud and the flower bud. Are there any differences? If so, describe.

2. Prunus triflora includes the following varieties: Ogon, Occident, Red June, Willard, Abundance, and several others.

a. Secure branches from one or more of the varieties named or others of the Prunus triflora that are available. Make a natural-size drawing of a branch four inches in length, showing the number and the position of the buds. Count from external appearance the number of fruit buds and branch buds. Measure the distance between the buds, and count the number in a cycle. Is the number constant? Discuss.

b. Make a drawing of a longitudinal and a cross section of both a branch bud and a flower bud. This drawing should show detail and be at least one inch in length. How many ovules do you find in the flower bud. Label all parts. Describe.

c. After a branch bud and a flower bud have been definitely determined, make a drawing showing each bud enlarged to one inch. What internal and external differences do you note? How can you distinguish the flower bud from the branch bud by external appearance?

d. Describe fully the difference between these buds and those of the Prunus domestiea and the Prunus triflora in gross appearance, in size, in location and arrangement, and in any other points noted by you.

3. Prunus americana includes the following varieties: Hawk-eye, De Soto, Weaver, Wood, Wyant, and some others.

a. Secure branches from one of the above varieties, including both fruit buds and branch buds, and make a drawing, natural size, and four inches in length. Note the color of the bark and the number of the lenticels. How does the Prunus americana differ from the Prunus domestica and the Prunus triflora in these respects? Describe fully.

b. Make a drawing, at least one inch in length, of both the branch bud and the flower bud. Are the buds arranged on the stem singly, or in clusters at the apex of a spur? Count the buds in each cluster, and note whether the number is constant or variable. Describe a fruit spur, and note how it grows. What is the direction of the growth? Why is this? Where do you find the branch bud? Has the position of the branch bud anything to do with the direction of the growth in the spur?

4. Prunus hortulana includes the following varieties: More-man, Wayland, World Beater, Golden Beauty, and several others.

a. Secure branches from one of the above varieties, including both fruit buds and branch buds. Make a drawing, four inches in length, and natural size, to show a twig which has both kinds of buds. Describe the color of the bark and the general appearance of the lenticels. Note any differences from the preceding groups.

b. Make an enlarged drawing of a fruit bud and a branch bud. Describe how the buds are arranged. Are they larger or smaller than those of the preceding groups? Discuss.

5. Prunus munsoniana includes the following varieties: Poole Pride, Pottawattamie, Newman, Robinson, Sophie, Wild Goose.

a. Make a drawing, natural size, and four inches in length, of a twig, including flower buds and branch buds. How do these buds differ from those of the preceding groups? Describe the buds, the lenticels, and the color of the bark.

b. Make an enlarged drawing, one inch in length, of a branch bud and a flower bud. Draw a separate scale of each. How do the scales differ? Are the buds arranged singly or in groups?

Comparative study of the plums. Describe in detail the points of difference between the branch buds and the flower buds in each group. Which are arranged singly, and which are in clusters? Count the ovules in at least ten different buds. Is the number constant? Describe any difference in the longitudinal and the cross sections of the buds in the different groups.

References

Bailey, "The Pruning Book," pp. 21-29, 46-50.

Goff, "Principles of Plant Culture," pp. 86-95.

Paddock and Whipple, "Fruit Growing in Arid Regions," pp. 66-80.