True hybrids between species may arise in quite the same way, and since it is obviously impossible to attribute them to an innate tendency to reversion, they afford an absolutely irrefutable proof of the assertion that pollen is often brought by insects from one lot of plants to another. In this way I obtained a hybrid between the common Jacob's ladder and the allied species _Polemonium dissectum_. With a distance of 100 meters between them I had two hybrid seeds among a hundred of pure ones. At a similar distance pollen was carried over from the wild radish, _Raphanus Raphanistrum_, to the allied _Raphanus caudatus_, and I observed the following year some very nice hybrids among my seedlings. A hybrid-bean between _Phaseolus nanus_ and _P. multiflorus_, and some hybrids between the yellow daisy, _Chrysanthemum segetum_ and the allied _Chrysanthemum coronarium_ or ox-eye daisy which also arose spontaneously in my garden between parents cultivated at recorded distances, might further be noted. Further details of these experiments need not be given. Suffice to say, that occasional crosses between species do occur, and not even rarely, that they are easily recognized as such and cannot be confused with cases of atavism, and that therefore they give proof to the assumption that in the same way crosses ordinarily occur also between varieties [203] of the same species, if cultivated at small distances apart, say 40-50 meters or even more. Vicinism therefore, may play a part in all such cultures, enough to account for all the impurities observed in the nurseries or in commercial seed-samples. Of course this whole discussion is limited to such species as are not only as a rule visited by insects, but are dependent on these visits for their fertilization. Most of our garden-flowers are included in this category. If not then we may expect to find the cultures and seeds pure, irrespective of the distances between allied varieties, as for instance with peas, which are known to be self-fertilizing. Another instance is given by the barley. One of the most curious anomalous varieties of this cereal, is the "Nepaul-barley," with its small adventitious flowers on the palets or inner scales. It is a very old, widely cultivated sort, which always comes true from seed, and which has been tested in repeated experiments in my garden. The spikelets of this curious plant are oneflowered and provided with two linear glumes or outer scales. Of the inner scales or palets, the outer one is three-lobed at the summit, hence the varietal name of _Hordeum vulgare trifurcatum_. The central lobe is oblong and hollow, covering a small supernumerary floret inserted [204] at its base. The two lateral lobes are narrower, sometimes linear, and are often prolonged into an awn, which is generally turned away from the center of the spike. The central lobe sometimes bears two florets at its base, although but one is usually present and it may be incomplete.