Page:Popular Science Monthly Volume 67.djvu/165

Rh certainly have been incomplete as to the whole crop and various as to the kinds of hybrids produced. Even if it were credible that the first case of complete aggregate mutation was due to fortuitous cross fertilization from some unknown source, it would still be too much to believe that exactly the same hybridizing process should have been repeated in the same manner in a following year. It may be added that there is now much reason to doubt that hybridization, although always imminent among tomatoes, has ever been so effective an agent in producing improved varieties of either plants or fruit as has been generally believed. Indeed,' saltatory mutation and racial variation have doubtless produced many of the results among plants that have been attributed to hybridization; although the latter has produced many wonderful results.

At the close of this narrative of experimental observations it is well to call special attention to the assumed fact that the mutative process which produced the new plant form that has been described was essentially separate from the accompanying process of fruit variation, although the two processes were intimately associated in both their origin and development. The plant mutation was from L. esculentum to L. solanopsis; the fruit variation was from the Acme to the Washington variety. The new fruit variety which accompanied the new plant form is of fine quality and therefore of horticultural value; but the origination of any fruit variety is, from a naturalist's point of view, of far less importance than the origination of a species. Plant mutation produces species which are real entities. Fruit variation is limited to changes in the pericarp; and the most improved and heritable fruit variety thus produced may, by degeneration, become disassociated from the plant entity without any impairment of that specific condition.

There are two extraordinary features of the foregoing narrative of my observations. One of them relates to the sudden and complete mutation of every plant of a crop of twenty-four Acme tomato plants to another specific plant form bearing a new variety of fruit. The other relates to a subsequent exact duplication of that mutation in all its details as to both plant and fruit, in a crop of thirty plants, also of the Acme variety. It is apparent that both cases were initiated and consummated in the plants while they were growing in my garden because the germ cells which gave origin to the mutated plants were all formed there; and the mutated plants were there grown to maturity. Another fact, important in this connection, although stated in a previous paragraph, is that this new specific form had been previously produced by gardeners, who had given to it the name of potato-leafed tomato. That is, this one and the same species, L. solanopsis, has arisen suddenly and independently from L. esculentum at not less than three different times, each in a different locality.