6o INTRODUCTION 



Pontederiaceae : Heteranthera (not Monochoria) Kotschyana Fzl, H. reniformis, 

 H. spicata, H. callaefolia, H. Potamogeton, and other sp. (Solms-Laubach). 



Commelinaceae : Commelina bengalensis (Weinmann), Tradescantia erecta 

 (Henslow). 



Juncaceae : Juncus (Darwin), J. capitatus (Buchenau), J. pygmaeus (?, Buchenau). 



Gramineae : Hordeum (Darwin), H. vulgare (a few flowers, Delpino), Crypto- 

 stachys (Darwin), sp. of Stipa (Godron), St. pennata (Hackel), sp. of Bromus (Bei- 

 jerinck), Leersia oryzoides (Duval-Jouve, Ascherson, Kiefer), Amphicarpum, Danthonia 

 spicata and related sp. (Pringle and Asa Gray), Vilfa (Pringle), Diplachne serotina 

 (Janka and Hackel), Vulpia Myuros, sciuroides, and ciliata (Kiefer). 



Connected with cleistogamy is the so-called bud-fertilization, cases of which 

 have been more particularly observed in orchids, e. g. in Limodorum abortivum 

 (Freyhold), Thelymitra carnea and longifolia (Fitzgerald), Polystachya luteola 

 (E. Eggers), Polystachya zeylanica, Phajus villosus, and Calanthe inaperta (Moore), 

 Maxillaria rufescens (Reichenbach fil.). 



VII. Parthenogenesis. 



A few remarks may here be introduced concerning Parthenogenesis (virgin 

 reproduction) of flowering plants. The term signifies the formation of germinabk 

 seed without the aid of pollen. It is well known that the first observation on this 

 phenomenon was published by J. Smith (Trans. Linn. Soc, xxi, 1841, p. 509): 

 A female plant of the dioecious species Caelebogyne ilicifolia, grown in the Botanic 

 Gardens at Kew, from 1829, produced seed capable of germinating, necessarily 

 without previous fertilization. A. Braun, by examining a cultivated plant in the 

 Botanic Gardens at Berlin, established the correctness of Smith's observation and 

 compared the phenomenon with the parthenogenesis of insects discovered by 

 Th. v. Siebold (1856). Deecke, indeed, observed individual pollen-tubes, while 

 Baillon and Karsten saw isolated anthers in the otherwise purely female flowers, 

 but A- Braun's further observations ('Uber Polyembryonie und Keimung bei Caelebo- 

 gyne,' Berlin, i860) contradicted those of the botanists named. It was only in iB'jS 

 that Strasburger ('Uber Polyembryone,' Jenaische Zs. Natw., xii, 1878) cleared up the 

 matter by proving that this case finds an analogue in the occurrence of so-called adven- 

 titious embryos, e.g. in Funkia ovata, Allium fragrans, Euonymus latifohus, sp. of Citrus, 

 and others, in which individual nucellar cells in the neighbourhood of the embryo-sac, 

 grow into this as rounded bodies, that multiply by cell-division and develop into 

 adventitious embryos without the direct influence of fertilization. In Caelebogyne the 

 proliferating nucellar cells, which are growing into adventitious embryos, press upon 

 the disorganized egg-apparatus. This case, therefore, differs from the other only 

 in the complete suppression of fertilization, but is in complete agreement with it, 

 so far as concerns the development of adventitious embryos independently of fertiliza- 

 tion. And this proves that the embryo-production in Caelebogyne is not really 

 parthenogenetic, though further development takes place of an egg-nucleus that 

 remains unfertilized. It represents, on the contrary, a process of asexual reproduc- 

 tion, similar to the apogamy of many ferns, or the vivipary in spikelets of grasses 

 (Loew, ' Einfijhrung in die Blutenbiologie,' p. 296). 



