CHAP. VIII. LEEESIA. 335 



single case as yet known* of this grass producing in a 

 state of nature (in Germany) perfect flowers which 

 yielded a copious supply of fruit. Seeds from the cleis- 

 togamic flowers were sent by me to Mr. Scott in 

 Calcutta, who there cultivated the plants in various 

 ways, but they never produced perfect flowers. 



In Europe Leersia oryzoides is the sole representa- 

 tive of its genus, and Duval-Jouve, after examining 

 several exotic species, found that it apparently is the 

 sole one which bears cleistogamic flowers. It ranges 

 from Persia to North America, and specimens from 

 Pennsylvania resembled the European ones in their 

 concealed manner of fructification. There can there- 

 fore be little doubt that this plant generally propa- 

 gates itself throughout an immense area by cleisto- 

 gamic seeds, and that it can hardly ever be invigorated 

 by cross-fertilisation. , It resembles in this respect 

 those plants which are now widely spread, though they 

 increase solely by asexual generation.f 



Concluding Remarks on Cleistogamic Floivers. That 

 these flowers owe their structure primarily to the 

 arrested development of perfect ones, we may infer 

 from such cases as that of the lower rudimentary petal 

 in Viola being larger than the others, like the lower 

 lip of the perfect flower, from a vestige of a spur in 

 the cleistogamic flowers of Impatiens, from the ten 

 stamens of Ononis being united into a tube, and 

 other such structures. The same inference may be 

 drawn from the occurrence, in some instances, on the 

 same plant of a series of gradations between the 

 cleistogamic and perfect flowers. But that the former 

 owe their origin wholly to arrested development is 



* Dr. Ascherson, ' Bot. Zeitung,' cases in my ' Variation under 

 1864, p 350. Domestication,' ch. xviii. 2nd 



t 1 have collected several such edit. vol. ii. p. 153. 



