32 NATIVE BRITISH ORCHIDACE^ 



slits dividing them into six valves— three broad bearing the seeds, and three narrow, 

 often reduced to a single nerve, which are sterile. The valves remain joined together 

 both at base and summit. In dry weather the capsule contracts, opening the slits, 

 and the wind blowing through carries out the ripe seeds, easily wind-borne for long 

 distances owing to their extreme lightness. The vibration of the stiff stems displaced 

 by sudden gusts shakes out the seeds as from a pepper-pot. In some genera of epiphytic 

 orchids there are elater-like hairs on the valves which jerk out the seeds.^ In wet 

 weather the capsule lengthens, closing the valves, and protecting the seeds till fine 

 weather once more opens the slits. 



The number of seeds produced is enormous. Darwin found that a capsule of 

 Orchis macukta held 6200 seeds, so that a plant with 30 capsules would bear 186,000. 

 Allowing 400 bad seeds for each capsule, an acre would be thickly clothed by the 

 progeny of a single plant, the grandchildren would cover the island of Anglesey, 

 and^he great grandchildren, at the same rate of increase, would nearly clothe the 

 whole land surface of the globe with one uniform carpet of green.^ This is eclipsed 

 by Fritz MuUer, who found 1,756,440 seeds in a single capsule of a Maxillaria, and 

 the plant sometimes bears six such capsules. The reason for this stupendous production 

 of seed appears to be that not a single seed can germinate unless it falls on ground 

 where the appropriate species of "^i^pctonia is present, and unless hyphas actually 

 find their way into the extremely minute naicropyles of the embryos. 



PI F fig. 5 (p. 123), is a beautiful stereograph of the seed of Limodorum ahortivum 

 which shows in a wonderful way the glass-hke inflated testa with its reticulations, 

 whose excessive lightness makes the transport of the seed by air very easy. 



VI. HYBRIDISM 



In 1820 Reichenbach pat. wrote "naturam enim purissimam tales impuritates non 

 eisnere...certi sumus''.3 Natural hybrids were regarded as an offence agamst 

 The purity of nature. This idea blinded the eyes of botanists to their existence. 

 As any union between two distinct species would be unnatural, the findmg of a plant 

 intermediate between them was supposed to prove that the two species were one 

 and the same-the marriage was legalised by uniting them. Thus Hooker4 wrote to 

 Darwin- "The dismal fact you quote of hybrid transitions between Verhascum thapjus 

 and nigrum, and its bearing on my practice of lumping species through intermediate 

 specimens, is a very horrible one, and would open my eyes to my own blmdness 



T T> ji ^. rU t^fs rAf.-a ^ Darwin, Fert. Orch. ed. z, p. 278. 



3 S'^k^^Xi-fp.^^ '- ^ Hooker's Life an, Lexers, u, 34. 



