a large portion of a plant, and “out of a vast number of blossoms thus protected not a single one produced a pod, while the unprotected blossoms were for the most part fruitful.”  Mr. Belt gives a more curious case; this plant grows well and flowers in Nicaragua; but as none of the native bees visit the flowers, not a single pod is ever produced. (5/6.  Dr. Ogle ‘Popular Science Review’ 1870 page 168.  Mr. Belt ‘The Naturalist in Nicaragua’ 1874 page 70.  The latter author gives a case ‘Nature’ 1875 page 26, of a late crop of Phaseolus multiflorus near London which “was rendered barren” by the humble-bees cutting, as they frequently do, holes at the bases of the flowers instead of entering them in the proper manner.)

From the facts now given we may feel nearly sure that individuals of the same variety or of different varieties, if growing near each other and in flower at the same time, would intercross; but I cannot myself advance any direct evidence of such an occurrence, as only a single variety is commonly cultivated in England.  I have, however, received an account from the Reverend W.A.  Leighton, that plants raised by him from ordinary seed produced seeds differing in an extraordinary manner in colour and shape, leading to the belief that their parents must have been crossed.  In France M. Fermond more than once planted close together varieties which ordinarily come true and which bear differently coloured flowers and seeds; and the offspring thus raised varied so greatly that there could hardly be a doubt that they had intercrossed. (5/7.  ‘Fécondation chez les Végétaux’ 1859 pages 34-40.  He adds that M. Villiers has described a spontaneous hybrid, which he calls Phaseolus coccineus hybridus, in the ‘Annales de la Soc.  R. de Horticulture’ June 1844.) On the other hand, Professor H. Hoffman does not believe in the natural crossing of the varieties; for although seedlings raised from two varieties growing close together produced plants which yielded seeds of a mixed character, he found that this likewise occurred with plants separated by a space of from 40 to 150 paces from any other variety; he therefore attributes the mixed character of the seed to spontaneous variability. (5/8.  ‘Bestimmung des Werthes von Species und Varietat’ 1869 pages 47-72.) But the above distance would be very far from sufficient to prevent intercrossing:  cabbages have been known to cross at several times this distance; and the careful Gartner gives many instances of plants growing at from 600 to 800 yards apart fertilising one another. (5/9.  ‘Kenntnis der Befruchtung’ 1844 pages 573, 577.) Professor Hoffman even maintains that the flowers of the kidney-bean are specially adapted for self-fertilisation.  He enclosed several flowers in bags; and as the buds often dropped off, he attributes the partial sterility of these flowers to the injurious effects of the bags, and not to the exclusion of insects.  But the only safe method of experimenting is to cover up a whole plant, which then never suffers.