J Hattori Bot. Lab. No. 84: 57- 69 (July 1998) SPOROPHYTES OF TAKAKIA CERATOPHYLLA FOUND IN CHINA MASANOBU H!GUCHI 1 AND DA-CHENG ZHA a2 ABSTRACT . Results of morphological and anatomical studies of the sporophytes of Takakia cerato­ phy/la are presented based on Chinese plants. Taxonomic relationship of Takakia is discussed. Takakia ceratophylla has a unique capsule-wall thickening which functionally causes the incurve of valves. There is a regular spiral line of dehiscence on the capsule which is derived from two rows of epidermal cells less incra ssate at maturity and also on the green capsule. Spiral twisting of the cap­ sule and seta seems to be useful for more efficient spore dispersal. In several features the sporophytes of Chinese populations of this species are larger than those of the Aleutians. Takakia ceratophylla (Mitt.) Grolle has been known from Sikkim (Grolle 1963), East Nepal (Hattori et al. I973) and the Aleutian Islands (Sharp & Hattori 1967, Persson 1968, Smith 1978). In 1994, we made field researches in the north-western part of Yunnan Province, China. Fortunately we could find sporophytes and antheridial plants of Takakia ceratophylla at Mt. Meilixueshan, situated on the boundary between Yunnan and Tibet (Higuchi & Zhang 1994). This is the second discovery of the sporophytes of T ceratophyl­ la following the report from Atka Island, Aleutian Islands (Smith 1990, Smith & Davison 1993). It seems that Takakia has a higher level of sexual reproduction than was previously considered (cf. Hattori et al. 1974). D ESCRIPTION OF SPOROPHYTES Takakia ceratophylla (Mitt.) Grolle, Osterr. Bot. Zeitschr. 110 (4): 445, 1963. Lepidozia ceratophy/la Mitt., J. Linn. Soc. Bot. 5: 103, 1861. Fertile shoots erect, 6.8-10.8mm long (except sporophytes). Sporophytes terminal, monosetous, green in development, brown at maturity, consisting of a symmetric capsule, an elongate seta and a well-developed foot. Capsules erect, elliptic, gradually tapered at base and apex, I .6-2.3 mm long, 0.38--0.48 mm thick, dextrorsely spiraled more than 360° at maturity, exerted on an elongate seta, schizocarpous, dehiscence longitudinally along a single linear slit following the spiral of exothecial cells, beginning near the middle of the capsule and extending to the base and apex; capsule walls consisting of an epidermal layer of cells with pigmented wall-thickenings, subtended by 4-5 layers of thin-walled cells; su­ ture cells differentiated; operculum and peristome not differentiated; columella cylindric, consisting of 3-4 layers of thin-walled cells, reaching about 3/4 the inner space, overarched by the sporogenous tissue; exothecial cells subquadrate to rectangular, I 7.5- 55X10- 20 µm , thick-walled, dextrorsely arranged; stomata absent. Seta erect, straight, 1.2- 2.6 mm long, 0.12--0. I 8 mm thick, with central strand consisting of elongate thin-walled cells, dex- 1 Department of Botany, National Science Museum, 4- 1- 1 Amakubo, Tsukuba-shi, Ibaraki-ken 305, Japan. 2 Kunming Institute of Botany, Academia Sinica, Heilong Tan, Kunming, Yunnan 650204, China. 58 J. Hattori Bot. Lab. No. 84 I 9 9 8 Takakia Andreaeobryum Fig. I. Diagrammatic cross sections of portion of exothec ial cells and outer surface views in Takakia and Andreaeobryum. Shadow areas show more thickened walls. Arrows point to the probable position of dehiscence. trorsely twisted. Foot well developed, tapered into the apex, penetrating to the gametophyte tissue, consisting of terminal quadrate cells with dense contents and upper elongate, thin­ walled cells. Spores produced in the whole inner space of the capsule, tetrahedral (with a triradiate ridge in proximal face), 32- 36 µm in diameter, brown, papillose in distal face, al­ most smooth in proximal face. Vaginules 0.4-0. 7 mm long, gradually tapered to the apex in cross-section, irregular at the top. Calyptra persistent, small, cucullate, smooth, irregular at the base, consisting of 1- 3 layers of delicate, hyaline cells, covering the top of capsule, sometimes remaining after dehiscing of the capsule wall. Specimens examined. China. Yunnan Province, Deqin County, Mt. Meilixueshan, Xiaonong, 3750 malt., 28 September 1994, Higuchi 25502, 25513, 25514 (TNS, KUN-HKAS). Takakia ceratophyl/a was found growing at the edge and overhanging part of rock on the slope at an elevation of about 3750m in the subalpine zone of Mt. Meilixueshan, and associated with Anastrophyllum assimile (Mitt.) Steph., Bazzania tricrenata (Wahlenb.) Lindb. and Gymnomitrion concinnatum (Lightf.) Corda. The size and growth form of plants are different in sheltered sites compared to exposed sites as those observed in East Nepal (Hattori et al. 1973). Sporophyte-bearing plants always occur with antheridial plants which are easily recognized by the orange-colored antheridia. They may occur singly or M. HIGUCHI & 0 .-C ZHANG: Sporophytes of Takakia ceratophyl/a 59 Fig. 2. Takakia ceratophylla (drawn by D. C. Zhang from Higuchi 255 13). I. Habit of fertile plants when dry (lower parts omitted). 2. Habit when wet. 3. Upper part of pl ant. 4. Upper part of plant with archegonium. 5. Cells at leaf tip. 6. Cross sections of leaf. 7. Cross section of stem. 8. Capsules. 9. Exothecial cells at middle part. 10. Spores (distal view). 60 J. Hattori Bot. Lab. No. 84 I 9 9 8 scattered, sometimes closely condensed. Sporophyte production is very low compared to the abundance of antheridia, which is similar to the case of Atka Island (Smith & Davison 1993). The development of sporophytes is not synchronous, which may result from the dif­ ference of the time of fertilization. As in most other mosses young setae and capsules are green. Sporophytes become elevated above the gametophytes not by means of a pseudopodium, but by elongation of the seta. There were observed some sporophytes of the previous year's production. However, there were no sporophytes appearing lateral due to subsequent innovative growth. It may be possible that the shoots with old sporophytes cannot live into the following year, because they are brown-colored without exception. The capsule-wall structure which Smith & Davison (l 993) did not mention is signifi­ cant, since it determines the mode and the effectiveness of spore dispersal. In Takakia cer­ atophylla capsule walls consist of an exothecial layer of cells with pigmented wall thicken­ ings, subtended by 4- 5 layers of thin-walled cells (Fig. 4: l O; Fig. 7: 6). The external walls of the exothecial cells are quite thick. The thickenings result in flask-shaped lumina in cross section of the exothecial cell s. There is a regular spiral line of dehiscence on capsules at maturity and also on the young green capsules (Fig. 5: 1, 2; Fig. 6: 3- 5). It means that the position of dehiscence is determined in early stages of development of the capsule. The line is derived from two rows of exothecial cells which have less-thickened walls (Fig. 4: 9, 11 , Fig. 6: 7). In Takaki a there are no specialized suture cells such as occur in A ndreaea and in hepatics, but the spiral line consisting of two rows of less-incrassate cells functions as a kind of suture cells. Exothecial cells are dextrorsely arranged even in early stages of development (Fig. 6: 2, 3). The seta is also dextrorsely twisted at maturity (Fig. 3: 5-7; Fig. 5: 5, 6; Fig. 6: 6). Capsules dehisce along the line from mid-capsule to the base and apex, and finally they appear as spiral ribbons (Fig. 3: 5- 7; Fig. 5: 7). After dehiscence the valve is incurved when dry. TAXONOMIC DISCUSSION The taxonomic position of Takakia remains disputable. Takakia has several peculiar features that are hepatic-like, moss-like or unique. Most of them are considered primitive. The fossi l record of non-vascular plants remains too imperfect to construct the evolution­ ary line of the primitive land plants (cf. Stewart 1983). The appearance of sporophytes of Takakia ceratophylla reminds us of those of the Late Silurian Tortilicaulis which resemble those of Takakia, not on ly in size but also in the elongate sporangia on unbranched twisted stalks (Edwards 1979). The relationship between those genera is uncertain, but their resem­ blance may denote one of the primitive features of Takakia. The discovery of its sporophyte-bearing plants distinctly advanced the discussion of the taxonomic position of Takakia . The idea that Takakia is a moss is supported by (I) the presence of columella (Fig. 7: 1, 2, 4-7), (2) calyptra protecting the top of sporophytes (Fig. 5: 2, 3; Fig. 7: 3), (3) the stoutness and the persistence ofsporophytes, (4) the absence of elaters, (5) the elongation of seta before the maturity of sporangium, (6) the twisting of seta consisting of thick-walled cells, (7) the tapered foot (Fig. 8: 2, 3) and (8) the long term of the release of spores. While putting it in mosses, some of the gametophytic characters in M . HIGUCH I & D.-C. ZHANG: Sporophytes of Takakia ceratophylla 61 T ! 1 T ! 1 2 3 4 5 6 7 Fig. 3. Takakia ceratophylla (drawn by M. Higuchi from Hig uchi 25513). I. Young sporophyte. 2- 7. Capsules viewed from different sides. 2, 3. Fully dehisced capsules when wet. 4. Just dehisced capsule when wet. 5- 7. Fully dehisced capsules when dry. Arrows show calyptrae. Takakia are unique. We consider the taxonomic position of Takakia to be as follows. Division : Bryophyta Class: Musci Subclass: Takaki idae Subclass: Andreaeidae Subclass: Sphagnidae Subclass: Bryidae Class: Hepaticae 62 J. Hattori Bot · La b ·No. 84 I 9 9 8 M. HIGUCHI & D.-C. ZHANG: Sporophytes of Takakia ceratophyl/a 63 Sporophytes of Chinese plants were compared to the description of sporophytes by Smith & Davison (1993). A striking difference is noted in the size of sporophytes.