NATURAL HYBRIDS. 583 



identified, and this fact is of no little significance when taken in connection with 

 the circumstance that Europe only possesses 41 species of Conifers. Juniperus 

 Kanitzii, the hybrid offspring of Juniperus communis and /. sabinoides, is a very 

 instructive instance owing to the great diversity in the form of the two parent- 

 species. 



Comparatively few hybrids occur amongst Grasses. The majority belong to the 

 genus Calamagrostis. Strangely enough, most hybrid grasses have arisen from crosses 

 between species of different genera, as, for instance, Festuca and Lolium, Triticum 

 and Elymus, Triticum and ^Egilops. The hybrid derived from ^Egilops ovata and 

 Triticum sativum, and known by the name of JEgilops triticoides, and the hybrid 

 ^Egilops speltceformis, obtained by crossing JEgilops triticoides with Triticum 

 sativum, have been the subject of lively discussion in their time, and have contri- 

 buted not a little to clearing up our- ideas concerning hybrids. As a set-off to the 

 Grasses, the groups comprising Reeds, Rushes, and Sedges include a comparatively 

 large number of hybrids. For example, in the genus Carex instances have been 

 discovered in the most widely different localities. 



Amongst Lilifloreae and Iridese only a few wild hybrids have been found, but 

 on the other hand a large number occur amongst Orchidacese all over Europe. Tt 

 is striking how many of these Orchid hybrids spring from species which are placed 

 by Botanists in different genera. Hybrids are known, for instance, which are derived 

 respectively from Acer as and Orchis, from Anacamptis and Orchis, from Ccelo- 

 glossum and Orchis, from Gymnadenia and Orchis, from Himantoglossum and 

 Orchis, from Serapias and Orchis, from Gymnadenia and Nigritella, and from 

 Epipactis and Cephalanthera. The hybrid Epipactis speciosa, lately discovered in 

 the Erlafthal of Lower Austria, is the result of a cross between Epipactis rubigi- 

 nosa and Cephalanthera alba, and is of special interest on account of its manifesting 

 characters strongly resembling those of species indigenous to regions at a great 

 distance from the place where the hybrid occurs, for at first sight Epipactis speciosa 

 might easily be taken for Epipactis gigantea, which is a native of North America,, 

 or for the Japanese species named Epipactis Thunbergii. 



Hybrids are comparatively numerous amongst the Pond-weed group (Potamo- 

 geton). These are aquatic plants which discharge their pollen in the form of clouds- 

 of dust, and at the season of pollination raise their flowers above the surface of the- 

 water. Owing to their being completely protogynous (see p. 310), autogamy is out 

 of the question. The crossing of pairs of species is especially promoted by the- 

 circumstance that the different species flower in definite succession, so that always 

 just at the time that one species is terminating its period of bloom another is- 

 coming into flower. 



Plants which have their flowers in catkins (amentaceous), such as Oaks, Birches,. 

 Alders, Poplars, and Willows, produce an uncommonly large number of hybrids. 

 In Willows pollination is effected by insects, in the other genera by the wind. This, 

 gives occasion for us to raise, in connection with this group, the question whether 

 hybrids originate more frequently from entomophilous or from anemophilous plants. 



