Transactions of the Horticultural Society 5: 377-380 (1824)
LVIII. Some Remarks on the supposed Influence of the Pollen, in cross breeding,
upon the Colour of the Seed-coals of Plants, and the Qualities of their Fruits.
By THOMAS ANDREW KNIGHT, Esq. F. R. S., &c. President.
Read June 3, 1823.
|* See page 234 of this Volume.|
IT has been long ago ascertained by physiologists, that the seed-coats, or membranes which cover the cotyledons of the seeds of plants, with the receptacles which contain such seedcoats, are visible some time before the blossoms acquire their full growth; and the existence of these organs is, therefore, obviously independant of the influence of the pollen upon the growth of the internal and essential parts of the future seeds. The seed-coats also, and the fruit of some species of plants, acquire nearly, if not wholly, their perfect growth when the pollen has been intirely withheld, or when, from other causes, it has not operated; and from these circumstances, and other observations, it has been inferred, that neither the external cover of the seeds, nor the form, taste, or flavour of fruits, are affected by the influence of the pollen of a plant of a different variety or species. There exists, however, some difference of opinion upon these points; and the experiments of Mr. GOSS upon the Pea, of which an account is given in a Paper recently printed in the Transactions of the Horticultural Society,* appear strongly to countenance the opinion, that the colour of the seed-coats at least, may be changed by the influence of the pollen of a variety of a different character; and hence he infers, with apparent reason, the probability that the taste and flavour of fruits may be also affected.
The narrative of Mr. GOSS is unquestionably quite correct; but I believe that there is an error in the inference which he has drawn; and I am anxious that such error, if it exist, should be pointed out; because it may occasion many experiments to be made to prove that, which I conceive to have been already sufficiently proved; and, consequently, cause the useless expenditure of time and labour, which might be advantageously employed in similar investigations upon other plants in the wide and unexplored field which lies open to the experimental Horticulturist.
The numerous varieties of strictly permanent habits of the Pea, its annual life, and the distinct character in form, size, and colour of many of its varieties, induced me, many years ago, to select it for the purpose of ascertaining, by a long course of experiments, the effects of introducing the pollen of one variety into the prepared blossoms of another. My chief object in these experiments was to obtain such information as would enable me to calculate the probable effects of similar operations upon other species of plants; and I believe it would not be easy to suggest an experiment of cross breeding upon this plant, of which I have not seen the result, through many successive generations. I shall, therefore, proceed to give a concise account of some of these experiments, or rather (as I wish not to occupy more than necessary of the time of the Society), to state the results of a few of them, believing that I shall be able to explain satisfactorily, the cause of a coloured variety of the Pea having been apparently changed into a white variety, by the immediate influence of the pollen in the experiment of Mr. GOSS.
When, in my experiments, the pollen of a gray Pea was introduced into the prepared blossoms of a white variety, no change whatever took place in the form, or colour, or size, of the seeds; all were white, and externally quite similar to others which had been produced by the unmutilated blossoms of the same plant. But these when sown in the following year, uniformly afforded plants with coloured leaves and stems, and purple flowers; and these produced gray Peas only. When the stamens of the plants which sprang from such gray Peas were extracted, and the pollen of a white variety, of permanent habits, was introduced, the seeds produced were uniformly gray; but many of these afforded plants with perfectly green leaves and stems, and with white flowers, succeeded, of course, by white seed. In these experiments the cotyledons of all the varieties of Peas employed or produced were yellow; and, consequently, the Peas with white seedcoats retained their ordinary colour, though they contained the plumules and cotyledons of coloured Pea plants. The cotyledons of the Blue Prussian Pea, which was the subject of Mr. GOSS'S experiments, are, on the contrary, blue; and the colour of these being perceptible through the semi-transparent seed-coats, occasioned those to appear blue, though they are really white; the whole habits of that plant are those of a white Pea. The colour of the cotyledons only were, I therefore conceive, changed; whilst the seed-coats retained their primary degree of whiteness. I must consequently venture to conclude, that the opinions of Mr. SALISBURY, quoted by Mr. GOSS, which have also very long been mine, viz. that neither the colour of the seed-coats, nor the form, taste, or flavour of fruits, are ever affected by the immediate influence of the pollen of a plant of another variety or species, are well-founded.
I need not add, that Mr. SETON'S experiment mentioned in the note to Mr. GOSS'S Paper, is also most perfectly accurate; though the results differed from those obtained by Mr. GOSS, owing, I imagine, to the greater permanence of colour in the cotyledons of the Green Imperial Pea, which was the subject of his experiments.