100 THE PHENOMENON OF 



to the fruit; so, just as in the ascent from calyx- to 

 stamen-formation, the corolla lies between the two, we 

 again find the petal formation, as a perigynium, in the 

 descent from the stamen -formation to the fruit-formation. 

 In many Limes the similarity between the periyynium 

 and the corolla is perfect, while in other species of the 

 same genus normally developed stamens occupy its place. 

 The resemblance to petals is less marked in the peri- 

 gynmm of the Byttneriaceae and Dombeyaceae; in the 

 Malvaceae, especially distinctly in Hibiscus, it forms 

 the inside of the tube, from the outside of which the 

 circles of stamens pass off at various heights. 



Lastly, we have still to consider the cases in which, at 

 the last stage of transition of the metamorphosis, the 

 suppression acquires such extent, that the entire stamen- 

 formation becomes involved, or, on the reverse, this exists, 

 and the fruit-formation is suppressed. The necessity 

 of these two formations to propagation, makes it a con- 

 dition that, in such cases, the plant bears two kinds of 

 flowers, staminate (male) and pistillate (female) flowers, 

 united on the same " stock," or distributed on distinct 

 "stocks." Examples of this kind occur not merely 

 scattered singly in the most diverse families, but there 

 are even entire families in which this condition appears as 

 the rule. To the former belong dioecious species of the 

 genera Lychnis, Silene, Ehamnus, Rumex, the genus 

 Rhodiola of the family of Crassulacese, the genera Smilax 

 and Euscus, of the alliance of Liliese, and Zea and Coix 

 among the Grasses ; to the latter belong the Palmae and 

 Cucurbitaceae. In all these the male and female flowers 

 have the same type, but differ in the completion, since 

 the plant is incapable of combining the contrast of stamen- 

 and fruit-formation within the ideally limited space of one 

 flower. In the male flower the leaf- formation sinks down 

 after bringing forth the stamens, without acquiring 

 power to rise again to fruit- formation ; in the female 

 flower the latter is attained by an earlier retrogres- 

 sion of the leaf-formation, suppressing the stamens, 



