VEGETATION OF THE NEW JERSEY PINE-BARRENS pp. 292-294 (1916)
John W. Harshberger, PH.D.

VIVIPARY IN THE ACORNS OF QUERCUS MARYLANDICA

*GUPPY, H. B.: Studies in Seeds and Fruits, 310 and 432.

On September 5, 1912, at Spring Lake, New Jersey, an oak tree of this species was found with a viviparous acorn. This condition was induced probably by the heavy rains, followed by mists and fogs, that had prevailed for a few days previously. An examination of this acorn showed that the embryo had swollen sufficiently to crack open the acorn covering, which had started to glaze. This splitting of the acorn shell revealed the presence of a small lenticular acorn at the base and inside the margin of the cupule. This vivipary of the acorns has not been studied exhaustively in America, but in Europe it has been studied in Quercus robur. Guppy* states that this is exhibited, not only in the occasional germination of the fruits on the tree, but in the actual stages of growth of the seed within its shell before maturity is reached. The steady growth of the seed on the tree long after the pericarp, or shell, has begun to dry is noteworthy. The vital connection with the parent plant is maintained by the attachment of the base of the fruit to its cupule. When the acorn begins to brown this attachment to the cupule begins to loosen, the result evidently of the drying of the pericarp, or shell. In the case of the viviparous acorn, it falls to the ground and usually dies, but it must happen frequently in moist mild weather that it continues the growth commenced on the tree, and if covered by protecting leaves, it may survive to the next spring and grow into an oak tree. Guppy suggests in connection with this viviparous habit, that if acorns are taken before they enter the rest period, that is while the pericarp is still green but the embryo is mature, they can be induced to keep up an uninterrupted growth without entering the rest period. This suggestion was tested with a number of acorns of species of oak, viz., Quercus alba, Q. marylandica, Q. prinus. Acorns of these three species were planted in a box filled with sphagnum. The planting was done on September 12, 1912, and the results recorded on October 22, 1912. Two series of acorns were sown. One set had a portion of the shell removed, exposing the embryo. The other set was planted with an uninjured shell covering. There was a slight advantage in the rate of germination of the cut acorns, as contrasted with the uncut. Practically all of the green acorns of the chestnut oak, Quercus prinus, the white oak, Q. alba, and the black-jack oak, Q. marylandica, germinated (Fig. 267).

*SACHS, JULIUS: The Physiology of Plants: 350.
GUPPY, H. B.: Studies in Seeds and Fruits: 421.

Sachs* and other botanists have maintained that, even under the most favorable conditions of vegetation, dormant periods occur in the course of the life of the plant. Under circumstances when the plant would be in a condition to grow most vigorously, because it is provided with reserve materials, water and oxygen are at its disposal and a sufficiently high temperature might be expected to call forth the internal activities, yet every externally perceptible vital motion nevertheless ceases, and it is only after some months of rest that the growth commences anew, and this frequently under circumstances which appear far less favorable--especially at a conspicuously lower temperature. The experiments with acorns detailed above and experiments performed by Guppyć with the seeds of Iris pseudacorus, Vicia sepium, Arenaria peploides and Quercus robur show that a rest period is not essential for the germination of acorns and other seeds, but that by taking immature acorns, whose embryo has not ceased to grow, and planting them the period of growth is maintained without cessation, or a rest period, and the result is the elongation and growth of the embryo into a young seedling plant, as fully demonstrated in the figures. The germinative capacity of so-called unripe seeds does not seem to have been appreciated by foresters and gardeners, who layer their tree seeds in boxes of sand kept slightly moist and stored in a cool place over the winter. The acorns can be planted while green and carried over the winter in the greenhouse in the actively growing condition and in the spring, they can be planted in the open (Fig. 267).


FIGURE 267
Stages in vivipary of Quercus marylandica
A, Acorn of Quercus marylandica. E, F, G. Later stages of vivipary.
B, Acorn of Quercus marylandica dissected. H, I, Stages in germination of green acorns of Quercus marylandica.
C. Embryo of Quercus marylandica. J. Stage in germination of green acorn of Quercus alba.
D. First stage of vivipary in acorn of Quercus marylandica. K. Details of such germination.