DEGENERACY OF FLOWERS. 2G5 



Now, the three genera of Grasses here mentioned are 

 characteristic of Avarmer regions, and even tropical, Leersia 

 oryzoides being the sole species of that genus which reaches 

 Europe, where it becomes cleistogamous. Therefore climatal 

 conditions niaj, with some reasonable presumption, be sug- 

 gested as the immediate cause in these cases. With regard to 

 Hordeum murinum, which is, perhaps, almost habitually cleis- 

 togamous in this country, it may be an hereditary result 

 issuing from a similar cause. This may also apply to Viola; 

 for not only are some species tropical, but all the genera 

 most nearly allied to Viola are tropical also. This is analo- 

 gous to what I have suggested as the origin of gynodioecism 

 in Lahiatce, which it may be noticed has at least two genera 

 with cleistogamous flowers in this country or Europe. Juncus 

 hufoniiis, according to Batalin, is exclusively cleistogamous 

 in Russia, hence the same cause suggests itself for this 

 species ; for, according to Ascherson, at Halle it has ordinary 

 open, lateral, hexandrous flowers in addition to terminal 

 cleistogamous triandrous ones.* This seems to show that 

 lessened vigour has also a hand in the process in this case : 

 the mean temperature of Halle is probably higher; if so, it 

 may cause the plant to bear the open flowers there. 



From the above-mentioned facts, it will be seen that 

 there may be more than one cause to account for cleistogamy. 

 Hence, it must be regarded as an inevitahle result whenever 

 those influences are brought to bear upon the plant which 

 are capable of producing it ; and there is every reason to 

 believe that whatever effects are produced iu plants by 

 external stimuli, if the latter be permanently kept up they 

 will become hereditary, and then will be recognized by 

 systematists as specific or generic characters. 



Anemophilous, or Wind-feetilised Plants. — The general 



* Miiller, I.e., p. 561. 

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