62 INTRODUCTION 



Other known cases of parthenogenesis occur among orchids, grasses, and 

 Hippeastrum ; on the other hand, according to Bonavia (Gard. Chron., London, viii, 

 1890), the development of embryos of Ficus Roxburghii without pollen, as observed 

 by Cunningham (loc. cit.) has not been sufficiently proved. 



A. Ernst (' A new case of Parthenogenesis in the vegetable kingdom ') found 

 that in Disciphania Ernstii EichL (in Caracas) two plants produced an increasing 

 number of fruits in three successive years, although the nearest male plants were 

 nine miles away from the place of observation, so that there could be no question 

 of cross-fertilization \ 



VIII. Flower- Groups. 



As already mentioned on p. 1 4, Delpino, in his work ' Ulteriori osservazioni 

 suUa dicogamia nel regno vegetale,' has arranged the floral mechanisms known to 

 him in adaptational groups, and so has established a classification of plants according 

 to their mode of fertilization. His scheme, which embraces the whole vegetable 

 kingdom, is as follows : 



A. ZooGAJiAE : plants with reproductive elements capable of movement. Among 

 these are most of the Cryptogams, in which the spermatozoids are motile. 



B. DiAMESOGAMAE : plants in which the reproductive elements require external 

 means of conveyance. 



I. Hydrophilae {Water-pollinated Plants) : plants which are pollinated 



by the agency of water, 

 (a) Pollination is effected under water : the pollen-grains or the spores possess 



the specific gravity of water : Posidonia, Cymodocea, Zostera, Cerato- 



phyllum, Florideae. 

 {b) Pollination is effected on the surface of the water : the pollen is lighter 



than water, or is borne on a float ; the stalks of the female flowers grow 



up to the surface of the water : Ruppia, Vallisneria. 



II. Anemophilae ( WiJid-pollinated Plajits) : plants which are pollinated 



by the agency of wind. 



{a) Wind-pollinated plants without stigma: Gymnosperms. 



(3) Wind-pollinated plants with stigma this being usually well developed. 



1. Catkin form [typus amentiflorus) : the male inflorescences have long movable 

 axes (Corylus, Betula, and so forth). 



2. Form with pendulous flowers {typus petiduliflorus) : Negundo fraxinifolium, 

 Rumex. 



3. Forju ivith long movable filaments {typus lo7igistamineus\ This very common 

 form of wind-pollinated flower occurs in almost all Gramineae, Cyperaceae, and 

 Juncaceae, also in Cannabis, Humulus, Mercurialis, Ricinus, Plantago, Litorella, 

 sp. of Callitriche, Myriophyllum, Hippuris, and others. 



4. Form with elastic explosive stamens {typus explodens) : Urtica, Parietaria. 



^ [Other cases have been recorded since the publication in 1898 of the German text. A useful 

 summary with references to the literature will be found in Coulter and Chamberlain, ' Morphology 

 of Angiosperms,' New York, 1903. Ed.] 



