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 J. 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 Calainagrostis. 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 jEgilops. The hybrid derived from ^gilops ovata and 

 Triticuvi sativum, and known by the name of jEgilops triticoides, and the hybrid 

 JEgilops speltceformis, obtained by crossing ^gilops triticoides with Triticuvi 

 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-ofi" 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 Liliflorese and Iridese only a few wild hybrids have been found, but 

 on the other hand a large number occur amongst Orchidaceae all over Europe. It 

 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 Aceras and Orchis, from Anacamptis and Orchis, from Coelo- 

 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 ruhigi- 

 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 occura, for at first sight Epipactis speciosa 

 might easily be taken for Ejnjxictis 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 {PotaTno- 

 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. 



