In these cases we come nearest to the direct causation or the direct inhibition of a division, but the meaning of the evidence is still ambiguous. I incline to compare Loeb's parthenogenesis with the development (and of course accompanying cell-division) of dormant buds on stems which have been cut back. It is interesting to note that sometimes as an abnormality, the faculty of division gets out of hand and runs a course apparently uncontrolled. A remarkable instance of this condition is seen in _Begonia_ "_phyllomaniaca_", which breaks out into buds at any point on the stem, petioles, or leaves, each bud having, like other buds, the power of becoming a new plant if removed. We would give much to know the genetic properties of _B. phyllomaniaca_, and in conjunction with Mr. W. O. Backhouse I have for some time been experimenting with this plant. It proved totally sterile. Its own anthers produce no pollen, and all attempts to fertilise it with other species failed though the pollen of a great number of forms was tried. Recently however we have succeeded in making plants which are in every respect _Begonia phyllomaniaca_, so far as the characters of stems and leaves are concerned. These plants, of which we have sixteen, were made by fertilising _B. heracleifolia_ with _B. polyantha_. They are all beginning to break out in "phyllomania." As yet they have not flowered, but as they agree in all details with _phyllomaniaca_ there can be little doubt that the original plant bearing that name was a hybrid similarly produced. The production of "phyllomania" on a hybrid Begonia has also been previously recorded by Duchartre.[17] In this case the cross was made between _B. incarnata_ and _lucida_. The synonymy of the last species is unfortunately obscure, and I have not succeeded in repeating the experiment. [Illustration: FIG. 5. Piece of petiole of _Begonia phyllomaniaca_. The proximal end is to the right of the figure.] From these facts it seems practically certain that the condition is one which is due to the meeting of complementary factors. At first sight we may incline to think that the phyllomania is in some way due to the sterility. This however cannot be seriously maintained; for not only is sterility in plants not usually associated with such manifestations, but we know a Begonia called "Wilhelma" which is exactly _phyllomaniaca_ and equally sterile, though it has no trace of phyllomania. This plant arose in the nurseries of MM. P. Bruant of Poitiers, and has generally been described as a seedling of _phyllomaniaca_, but from the total sterility of that form this account of its origin must be set aside.