Studies in Seeds and Fruits pp. 421-422 (1912)

Unripe Seeds
H. B. Guppy

I found that embryos of Iris Pseudacorus, removed from their bed of albumen in the moist, uncontracted pre-resting seed and then placed in water, increased their length in a few days from 4 to 7 millimetres and displayed the plumular nob. The progressive growth of the embryo as the fruit grows and matures is in this plant very evident. Whilst the seed maintained much the same dimensions (7 millimetres), I obtained the following results for the growth of the embryo, in different stages of the fruit's development:—

Immature fruit embryo 1.55 mm. long
Ripe fruit before dehiscence 2-2.5
Fruit beginning to dehisce 3-4.5

With the object of inhibiting the rest-period and inducing pre-resting seeds to proceed at once with germination, I placed at different times a number of seeds of Iris Pseudacorus, Vicia sepium, Arenaria peploides, and Quercus Robur under favouring conditions in the moist, uncontracted state and obtained successful results. Thus, after keeping some of the freshly gathered, ripe, non-dehiscing fruits of the Iris in wet moss under warm conditions (60°-70 F.) between ten and fourteen days, I found that the drying of the fruits and seeds had been prevented and that some of the seeds were germinating. The full-grown, soft, uncontracted seeds taken from the green legumes of Vicia sepium behaved in the same way under the same conditions of experiment. In four or five days they commenced to germinate, and in five days the seedlings were half an inch long. The white, soft seeds from the green capsules of Arenaria peploides responded to my experiments precisely in the same fashion. So also with Quercus Robur, it is not difficult to procure the rapid germination of ripe acorns in September and October. If fresh green acorns of full size and still vitally connected with the cupule are placed in wet moss under warm conditions, some of them will be found germinating within a week.

The germinative capacity of so-called unripe seeds does not seem to have been fully appreciated by foresters, gardeners, and horticulturists, the advantages to be derived from dispensing with the rest-period being obvious. As subsequently shown, nature offers us some valuable suggestions in this direction in the case of the Oak. Many plants must afford similar indications. Thus Pfeffer points out (ii. 205) that the seeds of Senecio vulgaris and Stellaria media can germinate as soon as they are ripe. Take again the soft, scantily protected seeds of Pithecolobium filicifolium, the Bastard Tamarind of Jamaica. They germinate a few days after falling from the tree, or else lose their vitality altogether.