PARTIAL DICLINISM. 221 



the plants with small, usually pistillate flowers are chiefly 

 in blossom at the beginning of the flowering period of the 

 larger-flowered hermaphrodite plants of this section of the 

 CaryophyllecB. Similarly, Caffea arahica produces small pis- 

 tillate flowers in Guatemala at the beginning of the season. * 

 It is the same with Geranium macrorhizon and many species 

 of Pelargonium, €tc. f 



Gynodioecism also prevails in the Labiatoe, but both female 

 and hermaphrodite plants for the most part blossom simul- 

 taneously in summer. It may be noticed that the corolla is 

 almost invariably reduced in size in female flowers, whether 

 the species be strictly dioecious as in Bryony, or gynodioecious 

 as Thyme, showing the close interdependence between the 

 corolla and stamens. X 



That climatal conditions are likewise connected with 

 the Gynodioecism of the Labiatoe seems probable from the 

 behaviour of Thymus Serpyllum ; for Delpino found that it 

 was trimorphic in the warmer region of Florence, having 

 flowers with greatly developed stamens and the pistil in 

 every stage of abortion or even absent (see Chapter XXV.) ; 

 other flowers showed the exact converse ; and, lastly, others 

 were hermaphrodite. Miiller, however, on the other hand, in 

 Westphalia and Thnringia; Ascherson, in Brandenburg; 

 Hildebi-and, in the Rhine provinces ; and Mr. Darwin, in 

 England, never met with the purely male form ; though 

 Dr. Ogle found some with the pistil permanently immature. § 

 Similarly, Eriophorum angustifolium is gynodioecious in 

 Scotland and the Arctic regions.|| 



Besides temperature, the character of the soil has most 

 probably much effect in bringing about this kind of partial 



• Miiller, Fertilisation, etc., p. 304. + L.c, p. 158. 



J See Forms of Flowers, pp. 307-309. 



§ Miiller, I.e., p. 474. || Forms of Flowers, p. 307. 



