160 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. X, NO. 6. 



In speaking- more particularly of the ' ■ Commelinacese, this family figures quite often, and 

 sometimes very prominently so, in works on anatomical botany. De Bart" mentions several 

 points of great interest, derived from this family: The peculiar arrangement of the vascular 

 system; the structure of epidermis with the stomata; the occurrence of crystals; the root- 

 structure, etc. Falkenberg 6 describes the stem-structure of Tradescantia argi ntea and crassula, 

 also of Commelina Africa mi. Schwendenee" calls attention to the occurrence of collenchyma 

 and discusses the development of the mechanical tissue in some of the species. Van Tieghem'' 

 refers often to the Commeliinn; :> as a family of importance in anatomical respect. Furthermore 

 has Eberhard' described the structure of leaf and stem of a few species of Tradescantia, 

 Dichorisandra , ( 'am/nilu, and Sjiinmema, besides the distribution of starch, tannin, and chloro- 

 phyll in these species. The most comprehensive paper, however, is by Gravis', in which 

 Tradescantia Virginica is discussed from a morphological, anatomical, and physiological point 

 of view. Among the works dealing more particularly with the morphology of the family may be 

 mentioned those by Eichlerc and Schumann*, in which the diagram of the flower and the 

 structure of the inflorescence have been described and explained. Finally, in regard to the 

 germination may be cited Mirbel', who described seedlings of Commelina communis and 

 cristata, and Klebs- 7 , who has offered a most excellent contribution to the knowledge of the 

 morphology and biology of the germination. 



It is thus evident that the Commelinacea have already been studied from various viewpoints 

 and by authors of prominence. De Bary, Falkenberg, and Schwendener have no doubt 

 demonstrated the most interesting points to be observed in the anatomical structure: The fibro- 

 vascular system and the mechanical support. Eichleb and Schumann have elucidated the very 

 difficult points in respect to the flowers and inflorescences; in regard to the systematic treatment 

 of the family Hasskarl and Clarke have furnished us with specific diagnoses and sectional 

 divisions of the species, besides notes on the general habit and geographical distribution of these 

 interesting plants. 



However, when we examine the literature and consider the species that have been studied 

 more critically, it is readily noticed that relatively only a few species have been treated, and that 

 these, are mostly such as are frequently cultivated as ornamental plants. This is not so strange, 

 however, when we remember the exceedingly delicate structure of most of these plants, which 

 makes it necessaiy that they must either be studied from living specimens or from alcoholic 

 material. When plants of this family are pressed and dried for herbaria they lose their 

 structure to a very great extent, and this is the reason why so very few species have been more 

 closety investigated. The systematic treatment of the family may as far as concerns the external 

 character of flowers, fruits, and leaves be well drawn from herbarium specimens but, as in so 

 many other instances, the parts underground are seldom preserved, and are consequently passed 

 by in diagnoses. The rhizome and the roots have, as a matter of fact, received very little 

 attention; the ramification of the shoot and the anatomical structure of the vegetative organs in 

 general are, on the other hand, well known in some species, but entirely unknown in others. 



It would thus appear as if there is still something to be done in regard to investigating the 

 Commelinacese, and having had the opportunity of observing and collecting several species in the 

 field, and preparing these for further studies, we do not hesitate to present the results of our 

 investigations as acontribution to the knowledge of the family. As will be seen from the following 



« Vergleichende Anatoniie der Vegetationsorgane der Phanerogamen und Fame. 1877. 



'' Vergleichende Untersuchungen neber den Bau der Vegetationsorgane der Monocotyledonen. 1876. 



cDas mechanische Princip. 1871. 



''Traitc de Botanique. 1884. 



' Beitrage zur Anatomie und Entwickelung der Commelynaceen. [naug. diss. Hannover, 1900. 



/Rcrhi-ivlics aiiatoniiques et physiologiques sur le Tradescantia Virginica L. Bruxelles, 1S98. 



9 Bluthendiagramme. Leipzig, 1875. 



'' Neue Untersuchungen ueber den Bluthenanschluss. Leipzig, 1890. 



I Ann. duMus. d' hist. nat. Vol. 13, p. 54. 1809. 



3 Beitrage zur Morphologie und Biologie der Keimung. Untersuch. Hot. Inst. Tubingen. Vol. 1. L881-1885. 



