394 ANGIOSPERMAEMONOCOTYLEDONES 



2. Open, regularly self- fertilized flowers : Ophrys apifera Huds., Habenaria 

 intacta Benih,, Gymnadenia indenidXz. Hook., Habenaria hyperborea R. Br. (Darwin), 

 Epipactis atrorubens Schult. (Hermann Miiller), Epidendrum (F. Miiller). 



3. Occasional or exceptional autogamy : Neottia Nidus-avis Rich, (frequent), 

 and Listera ovata R. Br. (exceptionally) (Darwin). 



4. Never autogamous, but completely self-fertile. 



5. Completely self-sterile, but fertile with foreign pollen, not only of the same, 

 but of other species of the same genus ; species of Oncidium (J. Scott). 



6. Killed by geitonogamy ; species of Oncidium, Notylia, Gomeza, Stigmato- 

 stalix, Burlingtonia (Fritz Miiller). 



Ridley (J. Linn. Soc. Bot., London, xxiv, 1888) describes a still larger number 

 of orchids as cleistogamous or autogamous: Eulophia monophylla S. Moore, 

 Trichopilia fragrans Reichb., Dendrobium roseum Sw. (cleistogamous). He gives 

 (op. cit.) the following cases of autogamy : 



1. The pollen-grains separate from one another and fall from the anther 

 directly upon the stigma or on to the labellum, which comes into contact with 

 this : Ophrydeae, Neottieae, Thelymitra longifolia Forst., Spiranthes australis Lindl. 



2. Complete pollinia fall from the anther upon the stigma: Phaius maculatus 

 Blume, Chiloglottis diphylla R. Br., Arundina densa Lindl. 



3. Either the pollinia fall completely from the anther as before, or the bursicula, 

 caudicles, and disk remain attached to the column : Ophrys apifera Huds., Eulophia 

 monophylla /S". Moore, Trichopilia fragrans Reichb., Eria sp., Spathoglottis Paulineae 

 F. Mtiell. 



4. Overflow of stigmatic fluid : Cephalanthera pallens Rich., Epipactis atro- 

 rubens Schult., Spiranthes australis Lindl., Phaius WalHchii Lindl. ; and also Spatho- 

 glottis plicata Blume, Schomburgkia, Epidendrum, Cattleya, Thelymitra, Orthoceras, &c. 



Self-fertilizing species are thus very widely distributed (Justs bot. Jahresber., 

 Leipzig, xvi, (1888) 1890, pp. 561-2). 



The three sepals and the two upper petals frequently form a helmet-shaped 

 protecting roof for the inner parts of the flower. Of the original three stamens 

 there is generally only one present (rarely two), sessile on a column and bearing 

 the stigma on its anterior (upper) side in the form of a small, sticky, glandular 

 depression. The column frequently ends in a small process, the rostellum, 

 above the stigma ; behind it are situated one or two glands, entirely or partially 

 covered by a hood-like or elastic skin, which contain a tenacious, viscid fluid. 

 The filament is entirely united with the rostellum, so that only the anther is 

 visible ; this consists of two lobes which dehisce longitudinally each containing 

 a pollinium; the latter is made up of little packets of united pollen-grains, 

 which are fastened together by slender elastic threads into club- or pear-shaped 

 cohering masses. The lower end of the pollinia are firmly united with the glands 

 containing viscid substance. 



Pfitzer says that most orchids are distinguished by an exceptionally long period 

 of anthesis. Only a small number, such as the flowers of Sobralia, Restrepia, and 

 Cirrhopetalum, fade in a few days; in most genera the single blossoms remain 



J 



