Contributions to the Morphology of Sciadopitys verticillata

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1 14 Cytologia, Fujii jub vol. Contributions to Morphology Sciadopitys verticillata By Masato Tahara Biological Institute, Tohoku Imperial University, Sendai Sciadopitys verticillata SIEB. et ZUCC. is a conifer endemic to Japan. In 1910 LAWSON published an account concerng gameto phyte embryo this plant. His observation was not, however, complete, owg perhaps to paucity his material. present study was undertaken primarily to fill gap his vestiga tions. material used present research was obtaed from a large tree growg grounds Kameoka-Hachiman, a small shre suburbs Sendai. fixation was made by a strong chrom-acetic solution (1% chromic acid 100 cc, glacial acetic acid 3 cc) after dippg material to CARNOY'S solution for a few mutes. Section 7-25ƒÊ thickness were staed with NEW TON'S gentian violet iode. I. Male Gamete It is well known, that sperms found Cupressaceae Taxodiaceae are distctly organized cells that two sperms produced a pollen tube are exactly alike size struc ture that both have function fertilizg egg. But Abietaceae, cell division does not follow nuclear divi sion body cell as pollen tube is about to discharge sperms, boundary body cell becomes distct two sperm-nuclei are left free general cytoplasm pollen tube. Furrmore, archegonia beg separated from one anor by sterile tissue, only one two sperm-nuclei can function disparity size two sperm-nuclei is distct. Sciadopitys verticillata is generally considered as a member family Taxodiaceae. But several important pots, this plant differs from or members family. archegonia, for example, are separated by sterile tissue as Abietaceae; usual members Taxodiaceae form an archegonium complex. Concerng sperms, LAWSON describes m his paper on Sciadopitys verticillata, as follows: " division body -cell evidently takes place tip tube immediately over neck-cells archegonium it results, not formation two cells as Sequoia

2 1937 Contributions to morphology Sciadopitys verticillata 15 Cupresseae, but two free nuclei. From large number cases examed showg se stages, it became quite evident that re was no cell membrane separatg se two male nuclei from one anor. two structures were found lyg quite freely cytoplasm body cell, as is shown Fig. 12 one m is slightly but distctly larger than or." results my observations are totally different. pollen tube growg through upper part nucellus enters to archegonial chamber a few days before fertilization. Near end tube, pollen tube nucleus stalk cell nucleus a short distance behd elongated body cell are seen. nucleus body cell this stage development is always situated near extremity cell. division nucleus body cell takes place almost simultaneously with nuclear division central cell archegonium to form egg ventral canal-nucleus. resultg two nuclei are at first quite alike between m a cell plate is formed (Fig. 1). Thus a cell division occurs contradiction to LAWSON's description. Owg to posi tion nucleus body cell, cell is divided to two un equal portions (Fig. 2). Afterwards difference size struc Figs body-cell. Mitosis telophase. ~ two unequal sperm cells, pollen-tube nucleus stalk-nucleus. ~ same a later stage. ~450.

3 16 M. TAHARA Cytologia, Fujii jub. vol. ture se two cells becomes more evident fally most cases smaller one becomes entirely distegrated (Fig. 3). Accordg to LAWSON's description, sperm Sciadopitys verticillata closely resembles that Abietaceae. But my vesti gation shows that it is just like one found some members Taxaceae Podocarpaceae, where sperm is a distctly organized cell size-difference two sperms produced by division a body cell is quite evident. II. Ventral Canal Nucleus As already stated, a few days before fertilization nuclear division to form ventral canal nucleus egg nucleus occurs central cell archegonium. material collected on 11th June this year has shown a number se divisions. Fig. 4, a is metaphase this division. spdle is formed just under neck archegonium. A cross section ovule has fortunately shown polar view nuclear plate this division. chromosome number is clearly determed to be 10 (Fig. 4, b). Accordg to LAWSON haploid chromosome num ber this plant is 8. But recently SAX BEAL (1934) reported ir paper on chromosomes Cycadales that this plant has 10 pairs chromosomes diploid tissues. It is a remarkable fact that all or members Taxodiaceae Cupressaceae have 11 chromosomes haploid generation. Figs nucleus. ~400. 4, a. Mitosis b. metaphase same. to b. polar same form view. ~1600. polar ventral canal 5, view. ~1600. a. nucleus same anaphase egg ~ 400.

4 1937 Contributions to morphology Sciadopitys verticillata 17 In anaphase two halves chromosomes move toward opposite poles. v-shaped chromosomes assembled at ner pole form a compact group, while those at outer pole are scattered loosely lie almost a plane, just as metaphase (Fig. 5, a). So polar view latter enables us aga to determe easily exact number chromosomes (Fig. 5, b). In telophase nucleus formed at this pole is much compressed soon disorganizes. Cell division does not follow this nuclear division, as is usual with members Taxodiaceae. III. Proembryo My observations regardg fertilization are still complete will be reported a subsequent paper. first mitosis after fertilization was met with several times my preparations. Its position with archegonium varies accordg to circumstances. It may lie near middle archegonium or a little higher up same. In metaphase this division membrane fusion nucleus has already dis appeared spdle lies a mass dense cytoplasm. At begng this stadium we see two chromosome-groups. But se soon come toger form a spdle usual appearance. two nuclei resultg from first mitosis are at first small, but soon enlarge divide simultaneously to form four nuclei. se four nuclei pass to base archegonium, where three more free nuclear divisions take place also simultaneously 32 free nuclei are produced (Fig. 6-10). se 32 nuclei n become arranged three tiers, each which contas about 10 nuclei. cell-wall formation has its begng this stage. But this process is restricted to only middle lower parts embryo. Mean while 6th nuclear division takes place almost simultaneously. Text-fig. 11 shows prophase this division. Although I could not see metaphase this division, it is certa that long axis spdle division middle tier should be placed maly parallel to long axis archegonium, because we see a cross section this part embryo about same number cells fore begng after end this division. After this nuclear division formation cell-wall becomes completed. But uppermost tier, always some nuclei rema free without formg cell-wall ten, not always, some are found cells, distal ends which are open to general cyto plasm archegonium. Later cells middle tier become much elongated send group cells lowest tier toward center endosperm. 2

5 18 M. TAHARA Figs fertilization. development 7. In 1931 stage. nucleate BUCHHOLZ embryogeny described material fresh 8-nucleate proembryo. ~350. plant. figured by nucleate stage th published this Cytologia, Fujii jub. vo1 a him sugar 9. paper be solution 3rd. mitosis 5th mitosis. concerng remarkable could stage. mitosis. 32 later polyembryony confirmed stag 10. cleavage easily after by it dissectg with runium red. LAWSON's is rar description simple. formation nuclei free He early nuclei EAMES verticillata are 32 also Taxodiaceae. In highest or differs, It sts Conifers is 32 this at free family. Four family Arau brasiliensis refore' from level before Taxodiaceae embryo exist number Araucaria characteristic just reported australis. could to Abietaceae, Agathis nuclei accordg number found 64 development 8 free varies BURLINGAME found only cell-wall. common that embryogeny Cupressaceae. cariaceae. regardg believed or Sciadopitys members Araucariaceae.

6 1937 Contributions to morphology Sciadopitys verticillata 19 IV. Summary 1. In Sciadopitys verticillata cell division follows mitosis body cell. nucleus beg situated near extremity cell, two resultg cells show a remarkable dissimilarity size structure. 2. mitosis to form neck canal nucleus egg nucleus occurs just under neck cells archegonium. polar view spdle clearly shows 10 chromosomes. In anaphase, v-shaped chromosomes ner pole form a com pact group, while those at outer pole are scattered loosely lie almost a plane similar to those metaphase. polar view latter enables us to determe easily exact number chromosomes. 3. After fertilization 5 successive nuclear divisions occur produce 32 free nuclei before formation cell-wall. In conclusion I wish to express my hearty thanks to Mr. K. OIKAWA for assistance given me durg course present vestigation. Literature Cited Buchholz, John T. (1931): suspensor Sciadopitys. Bot. Gaz. 92. Burlgame, L. L. (1915): morphology Aracaria brasiliensis. III. Bot. Gaz. 59. Eames, A. J. (1913): morphology Agathis australis. Ann. Bot. 27. Lawson, A. A. (1910): gametophytes embryo Sciadopitys verticillata. Ann. Bot. 24. Sax, K., Beal, J. M. (1934): Chromosomes Cycadales. Jour. Arnold. Arb. 15.