334 CONCLUDING REMARKS CHAP. VIII. 



producing in a state of nature (in Germany) perfect 

 flowers which yielded a copious supply of fruit. Seeds 

 from the cleistogamic 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 sev- 

 eral exotic species, found that it apparently is the sole 1 

 one which bears cleistogamic flowers. It ranges from 

 Persia to North America, and specimens from Pennsyl- 

 vania resembled the European ones in their concealed 

 manner of fructification. There can therefore be little 

 doubt that this plant generally propagates itself through- 

 out an immense area by cleistogamic 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 a sex- 

 ual generation.* 



Concluding remarks on Cleistogamic Flowers. 

 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 sta- 

 mens 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 by no means 

 the case ; for various parts have been specially modified, 



* T have collected several snch mestication.' ch. xviii. 2nd edit, 

 cases in my ' Variation under Do- vol. ii. p. 153. 



