312 THE CROSSING OF FLOWERS. 



protoo"ynous. The same is true of Ericaceae, Valerianaceae, Polemoniaceae, and 

 many other groups. As far as we know, the Composites, Campanulacese, Labiatse, 

 Malvaceae, Caryophyllaceae, and Papilionaceous plants are exclusively protandrous. 

 Rushes and Woodrushes (Juncus and Luzida), Aristolochiaceae and Thymelacese, 

 Caprifoliaceae, Globularias, Solanaceae, Rosaceae, Berberidacese, and Cruciferae 

 exclusively protogynous. 



It has already been pointed out that the non-simultaneous maturation of the 

 sexual organs goes hand in hand with the separation in space of the two sexes in 

 most instances, or, in other words, that in plants where the two kinds of sexual 

 organs have in any way been separated from one another in the flowers by actual 

 distance, dichogamy also obtains. Thus, for example, it appears that all species of 

 plants w^hose hermaphrodite flowers are adapted to cross-fertilization by the relative 

 position and arrangement of their two kinds of sexual organs, or by the interchange 

 of position of anthers and stigmas are, moreover, dichogamous, although this dicho- 

 gamy may be only of slight duration. Plants with heterostyled flowers are also 

 dichogamous, since those with short-styled and those with long-styled flowers 

 develop at different times. If one observes the many hundred individuals of 

 Primula Auricula, growing side by side on a rocky crag under the same condi- 

 tions, it is easy to see that the plants with long-styled flowers are earlier than those 

 with short styles. The former are already over while the latter are in full bloom. 

 The reverse is the case in Auricula longifiora; here plants with short-styled flowers 

 are in full blossom when the long-styled flowers of the neighbouring plants are still 

 in bud. 



Plants bearing pseudo - hermaphrodite flowers are also dichogamous. The 

 Valerians ( Valeriana dioica, i^olygama, and tripteris) open their pistillate flowers 

 0-5 days before their staminate flowers in the same locality; these plants are 

 therefore decidedly protogynous. In the Alpine Dock (Rumex alpinus), the 

 stigmas of the pistillate flowers are ripe 2-3 days before the anthers of the 

 staminate flowers and of the truly hermaphrodite flowers on the same plant have 

 opened. In the Ash (Fraxinus excelsior), the stigmas of the pistillate flowers are 

 mature whilst the anthers in the neighbouring staminate and hermaphrodite 

 flowers are still closed. The latter do not usually shed their pollen till 4 days 

 later. The dichogamy of the Grasses, which bear both true staminate and herma- 

 phrodite flowers, is very striking (e.g. Anthoxanthum odoratum, Hierochloa 

 australis, Melica altissima, and Sesleria coirulea). In these plants the anthers do 

 not liberate their pollen until the neighbouring stigmas have been mature for two 

 days. This may also be observed in Composites whose capitula contain true herma- 

 phrodite and pistillate flowers, and in those with true pistillate and pseudo-herma- 

 phrodite male flowers. The stigmas of the pistillate flowers are already mature 

 two days before any pollen can be obtained from the adjoining truly hermaphrodite 

 or staminate flowers. It will suffice to mention as examples of this Aster alpinus, 

 Aronicum glaciate, Bellidiastrum Michelii, Doronicum cordatum, Erigeron 

 alpinum, Gnapihalium Leontoijodium, Tussilago Farfara, and Calendula offi.ci- 



