FERTILISATION. 77 



fertilisation than epiphytal ones, and that a large number of the latter 

 never set capsules ; hut from such incomplete data it is evident that 

 no just conclusion can be arrived at. 



The number of self-fertilising orchids is, however, considerable, and 

 additions to the list are frequently being discovered, but the total 

 number of known cases is still an almost infinitesimal fraction of the 

 whole number of species contained in the great Orchidean family. 

 Mr. Darwin mentions ten species in Fertilisation of Orchids, Mr. Forbes 

 adds those cited above and a few others ; the late Mr. Fitzgerald, the 

 author of the excellent monograph of Australian Orchids, and other 

 observers have added to the list ; and lastly, Mr. H. N. Ridley, in 

 some notes published in the Journal of the Linnean Society* gives 

 four others which he had himself examined, including Trichopilia 

 fragrans, which although frequently is not constantly self-fertilising. 

 Mr. Ridley also expresses his belief that among the small green-Howered 

 orchids of the tropics many more instances may be found. In the 

 four species to which his notes are chiefly confined, jNIr. Ridley traces 

 the cause of self -fertilisation, or Cleistogamy as it is technically called, and 

 proceeds to describe four common methods Ijy which this is eftected ; 

 to these methods we shall again refer. 



The epiphytal orchids observed in our houses to be cleistogamic or 

 self-fertilising fall under two categories — those that are habitually so, 

 and those that are not constantly self -fertilising. In the first category 

 are Chysis aiirea, Lindl., probably the first observed instance of cleisto- 

 gamy among epiphytal orchids ; Dendrohium cliry^eum, Rolfe, one of 

 the subjects of INIr. Ridley's notes ; an Australian form of Phaius 

 (jrandifolius, figured in the Botanical Magazine, t. 6032, under the 

 name of P. Bluniei Bernaysii (thus in a measure confirming Mr. Forbes' 

 observations on the Java form of the same species, but we have 

 never observed the typical P. grandifolius to be cleistogamic) ; to 

 these must be added Lcdia virens, Lindl., AcanthepMppiiom Curtisii, 

 Rclib., an inferior variety of Dendrohium Brymerianum from Upper 

 Burmah, and Cyprijjedium (Selenipedium) Schlimii, Batem.f In the 

 second category — those observed to be occasionally cleistogamic are D. 

 cretaceum, Lindl., D. aqueum, Lindl., D. crejiidatum, Lindl. ; and 

 among hybrids, Epidendrum x Ohrienianum and Calanthe x Giijas have 

 set capsules apparently without any external aid. In the case of 

 Cypripedium Schlimii and Epndendrum x Ohrienianum seedlings have 

 been raised from the capsules so produced, and the resulting progenie.s 

 liave conformed strictly to the parent plants.J 



* Vol. XXIV. p. 389. 



t On the self-fertilisation of this species, see Cypripedium, p. 68. 



X Epidendrum varieyfUum, occasionally seen in orchid collections, has been observed by Mr. 

 Hart, Superintendent of tiie Botanic Garden, Trinidad, to he cleistogamic in a wild state. In 

 a communication to the Gardeners' Chronicle (X.W^I., 1886, p. 11), he shows how self-fertilisa- 

 tion is effected in this species. 



