HETEROGA]MY AND AUTOGAMY. 201 



account for some mountain species, as well as those blossoming 

 early or in shady places, being protogynous. 



It must not be regarded as universally true. If flowers so 

 situated or circumstanced be abundantly visited by insects, 

 they will respond to their influence ; and the consequence is, 

 that many Alpine plants are even strongly protandrous, as 

 well as spring-flowering plants and some which grow in 

 shady places, as Sanicula Eurojpcea, Odontites serotina, etc. It 

 is Avhen we compare the protogynous species with others of 

 the same genus, that the influences of a lower temperature, 

 shade, etc., more especially suggest themselves as true causes 

 of protogyny in some species, while others may be homo- 

 gamous or protandrous. 



Many plants normally provided with conspicuous flowers, 

 but accidentally growing in shady places, may often be found 

 having them half opened or as quite closed buds, and yet 

 fully fertile. The same occurs late in the season, when the 

 flowering period is drawing to a close. Such flowers repre- 

 sent the preliminary stages leading to a permanently homo- 

 gamous or protogynous condition, as the case may be, which 

 are mostly autogamous as well. 



Whatever may be the direct cause, and there may be 

 others besides those I have mentioned, protogyny is easily 

 brought about temporarily in individuals, or it may become 

 hereditary and a permanent feature. 



It need now hardly be added that, before protogyny is 

 reached and emphasized, all degrees of passage can be met 

 with from strong to weak protandry ; then homogamy is 

 acquired : and, after passing through oscillating conditions, 

 permanent protogyny can be finally the result. 



Many individual plants vary in this respect, being some- 

 times or in some places in one condition, and at other times 

 and in other places in another condition. As nothing is 



