306 Cytologia 21 Cytological Studies in l-lelobiae, I. Chromosome idiograms and a list of chromosome numbers in seven families1 Ititaro Harada Biological Institute, Faculty of Science, Nagoya University, Nagoya Received Decemnber 27, 1955 Introduction As a part of the cooperative work on the karyotypic investigations of monocotyledonous plants, directed by Dr. Y. Sinoto, the writer has been studying the Order Helobiae since 1940. The writer will report the cytologi cal evidences, principally the karyotypic analyses in seven families of Helobiae. The Order Helobiae, otherwise called Helobiales, Fluviales or Najadales, is a unique group in Angiosperms, growing in aquatic habitat. Further, from several points of view, Helobiae is regarded as a systematically or phylogenetically important group. It is said that Helobiae is an ecological group involving those plants growing in fresh water or marsh and in sea or brackish water. "Sea grasses ", the submarine phanerogamous plants, are found solely in Helobiae. Growing surroundings of each genus are as follows2: 1. Potamogetonaceae emerg. flow. and some species with (Althenia) brackish water, submerged fl oat. leav. (Cynzodocea) sea water, submarine 4. Scheuchzeriaceae (Diplanthera) sea wat., submar. (Lilaea) marsh Phyllospadix sea wat., submar. (Maundia) marsh (Posidonia) sea wat., submar. Scheuclazeria marsh Potarnogeton fresh or brackish wat., sub (Tetroncimn) marsh merged, with floating leaves and Trigloehin freshwater marsh or seaboard emerging flowers. marsh Ruppia brackish or sea wat., submerg. 5. Alismataceae or submar. Alisma Zannichellia brack. or fr. wat., submerg. (Burnatia) 2. Najadaceae Caldesia Najas fr. wat., submerg. (Damasonium) 3. Aponogetonaceae Echinodorus Aponogetonn fr. wat., submerg., with (Elisma) fr. wat., submerg., 1 The principal part of the work was carried out from 1940 to 1950 at The Cytogenetical Laboratory, presided over by Dr. Yosito Sinoto, of Botanical Institute, Faculty of Science, University of Tokyo. 2 Classification of the genera is after Engler's sytem (Engler, A. and Diels, L. 1936. Syllabus der Pflanzenfamilien , llte Aufl.), Chromosome numbers of those in parenthesis have not as yet been studied. 1956 Cytological Studies in Helobiae, 1. 307 Limnophyton with float. leva. and leav. and emerg, flow. (Lophotocarpus) emerg. flow.; marsh Limnocharis marsh (Ranalisma) Tenagocharis marsh (Rautanenia) 7. Hydrocharitaceae Sagittaria Blyxa fr. wat., submerg. (Wiesneria) (Boottia) fr. wat., submerg., with emerg. 6. Butomaceae flow. Butomus marsh Elrodea fr. wat., submerg., with float. Hydrocleis fr. wat., submerg. with float. flow. Figs. 1-35. Potamogetonaceae. ca. •~2200. 1-2, Phyllospadix (RT): 1 a, P. iwatensis (•Š). 1 b, P. iwatensis (_??_). 2 a, P. japonica (•Š). 2 b, P. japonica (_??_). 3-22, Potamo geton (RT): 3, P. alpinus. 4, P. anguillanzcs. 5, P. apertus. 6, P. biwaensis. 7, P. crispus. 8, P. cristatus. 9, P. dentatzas. 10, P. distinctus. 11 a and b, P. Fauriei. 12, P. Fryeri. 13, P. gramineas. 14, P. lcanzogawaensis. 15, P. Maackianus. 16, P, malaianus. 17, P. malainoides. 18 a, b, c and d, P. mnonoginus. 19, P. natans. 20, P. nipponicus, 21, P, numasalcianas. 22, P. oxyphyllus. 308 I. Harada Cytologia 21 (Enhalus) sea wat., submar. emers., flow. Halophila sea wat., submar.H Ottelia fr. wat., submerg., with emerg, ydrilla fr. wat., submerg. fl ow. Hydrocharis fr. wat., submerg., with Stratiotes fr. wat., submerg., with emerg. float. leav. and emerg. flow. fl ow. (Lagarosiphon) fr. wat., submerg., with (Thalassia) sea wat., submar. emerg. flow. Trianea fr. wat., submerg. (Limnobium) fr. wat., submerg., with Vallisneria fr. wat., submerg. Figs. 23-35. 23-28, Potamogeton (RT): 23 a and b, P. panormitanus. 24, P. pectinatus. 25, P. perfoliatus. 26, P. praelongus. 27, P. pusillus. 28, P. Vaseyi. 29, Ruppia maritima. ca. x2200 . a (RT), b (PMC-I). 30, Zannichellia palustris. ca. x2200. a (RT), b (PMC-I). 31-35, Zostera. ca. x2200. 31, Z. asiatica (RT). 32, Z. caespitosa: a (RT), b (PG-I). 33, Z. caulescens: a (RT), b (PG-I). 34, Z. marina: a (RT), b (PMC I), c (PG-I). 35, Z. nana (RT). 1956 Cytological Studies in Helobiae, 1. 309 It is one of the writer's aims to reveal some relationship between these ecolo gical surroundings and the cytological evidences. So far, however, the writer has detected nothing tangible about it, especially about a plausible relationship between the aquatic habitat and the karyotypic characteristics. But some of the submerged limnetic species and, as far as studied, all species of submarine sea grasses exhibit respectively the characteristic pollen form and the polli Figs. 36-44. Najas. ca. •~1700. 36, N. ancistrocarpa (RT). 37, N. foveolata (RT). 38, N. gracillima (RT). 39, N. graminea (RT). 40, N. major: a and b (•Š, RT), c and d (_??_, RT), e (PMC-I), f and g (PG-I). 41, N. minor (RT). 310 I. Harada Cytologia 21 nation pattern, revealing an elaborate adaptation to the aquatic surroundings. For long it has been said by several botanists that Helobiae was a group having the phylogenetically most primitive type in Monocotyledons and could be regarded as a stock in the phylogenetical development of Monocotyledons. Moreover, many botanists have assumed that HeIohiae was standing in a joint Figs. 42-47. 42, N. oguraensis (RT). 43, N. tenuicaulis (RT): a (•Š), b (_??_). 44, N. sp. 45, Aponogeton distachyus, ca. •~2200. a (RT), b (PMC-I), c (PG-I). 46 and 47, Scheu chzeriaceae. ca. •~2200. 46, Scheaehzeria palustris (RT). 47, Triglochin maritimum: a and b (RT), c (PMC-I). ing point between Dicotyledons and Monocotyledons; especially a phylogenetical relationship between Ranales and Helobiae has been often discussed. The first cytological work on this problem was published by Liehr (1916). With the same idea, principally from the karyotypic standpoint , the present writer studied the chromosome number of some water plants in Ranales and of 1956 CytologicalStudies in Helobiae, I. 311 other dicotyledonous water plants (Harada 1952). Further, for a contribution to the cyto-phylogenetical relationship of Helobiae, the writer studied the chromosome number of Pandanales (Harada 1949 a), which is systematically arranged in closer rank to Helobiae in Engler's system and is also regarded as one of the more primitive groups in Monocotyledons. Considerations concern Figs. 48-53. Alismataceae. ca.•~1700. Figs. 48 and 49. Alisina: 48, A. eanatieutatum, a (RT), b (PMC-I). 49, A. orientale, a (RT), b (FMC-I). 50, Caldesia renaformis, a (RT), b (PMC-I). 51-62, Sagittaria: 51, S. ayinashi, a (RT), b (PMC-1). 52, S. falcata (RT). 53, S. montezidensis, a (RT), b (PMC-I). ing the cyto-phylogenetical relationships above mentioned will be reported in detail in later papers of the series "Cytological Studies in Helobiae" by the writer. 312 I. Harada Cytologia 21 In the present paper are given the idiogramatical figures of chromosomes of 22 genera of 7 families and a list of chromosome numbers of 27 genera including the results obtained by several authors. Although some of the figures in the text and of the numbers of chromosomes in the list were already reported by the writer, they are again included in the present paper, since Figs. 54-60. Aliomataceae. 54, S. natans, a (RT), b (PMC-I), c (PG-I). 55, S. platy phylla (RT). 56, S. pyymaea, a (RT), b (PMC-I), c (PG-I). 57, S. subulata, a (RT), b (PMC-I), c (PG-I). 58, S. trifolia (RT). 59, S. trifolia form. longiloba (RT). 60, S. trifolia form. plena (RT). most of them were published in preliminary brief notes in Japanese with or without figures, or printed as given in lectures before meetings of the Socie 1956 Cytological Studies in Helobiae, I. 313 ties. In later papers of this series the writer will report fully karyotypic an alyses of each group, i.e. of genera or of families, the microsporogenesis and the pollination of some species, and other cytological evidences in a number of species. Figs. 61-65. 61, S. trifolia form. ,jzitensis, a (RT), b (PMC-I), c (PG-I). 62, S. trifolia var. sinensis form. eoerulea, a (RT), b (PMC-I). 63-65, Butomaceae. ca. •~1700. 63, Butomus umbellatus (RT). 64, Hpdrocleis nym,phoides, a (RT), b (PMC-I). 65, Limno charis (lava, a (RT), b (PMC-I). Acknowledgment It is a pleasure to record here a debt of gratitude to Dr. Yosito Sinoto for his general guidance and his ceaseless encouragement given the writer to 314 I. Harada Cytologia 21 carry out this work, especially for his plotting the object of research, the karyo typic analysis of Helobiae. Further, the writer wishes to express his hearty thanks to Dr. Shigeru Miki1 who permitted the use at will of the several water plants cultivated by him for the writer's cytological materials, and who always rendered to the writer adequate aid in collecting the plants in several localities and identifying the names of species collected. The writer is in Figs. 66-78. Hydrocharitaceae . ca. •~2200. 66-68, Blyxa (RT): 66, B. ceratosperma. 67, B. Japonica. 68, B . sp. 69 and 70, Elodea: 69, E. canadensis, a (•Š, RT), b (_??_, RT), c (PMC-I). 70, E. densa, a (_??_, RT) , b (PMC-I). 71, Halophila ovata, a (•Š, RT), b (_??_, RT), c (PMC-I), d (PG-I). 1 Dr. S, Miki was until 1948 associated with The Botanical Institute, Faculty of Science, Kyoto University, and is now with The Institute of Polytechnics, Osaka City Unversity. 1956 Cytological Studies in H elobiae, I. 315 Figs. 72-78 . 72, Hydrilla zerticillata (RT). 73, Hydrochariss asiatica, a (RT), b (PMC I). 74, Ottelia alismoides , a (RT), b (PMC-diakinesis). 75-78, Vallisneria (RT): 75, V, asiatica, a (•Š) , b (_??_), c (unknown as to the sexuality). 76, V. asiatica var. biwaensis. 77, V.