Rearrangement of the Genera of a Hong Kong endemic species, Subglabrous dwarf bamboo 'Sasa subglabra McClure'

Owen et E.Ng

20th May, 2021.

CHINESE VERSION

Summary: Sasa subglabra McClure was collected and determinated on 1938, this Hong Kong endemic flora as an uncertain species due to insufficient scientific evidences, although many botanists have doubts about its genus of Sasa, based on the lack of  the flowering specimens, the taxonomic characteristics are still  not clear. Fortunately, we accidentally discovered that few of the mature plants were blooming during field visits in the end-spring season of this year, it is believed that this discovery may led to unlock the secret of the systematic position of this endemic species, this article also provides information on the inflorescences of the species.

Key words: Sasa subglabra McClure sensu lato,  Indocalamus subglabra (McClure) Ng et al., 2021,Genus: Sasa, Genus: Indocalamus, Lateral panicles.

Habitat: Sha Tin, Central New Terroritries, HONG KONG, only one spot in forest, partially shaded slope near ravine area, ca. 11,300m² (121,600 ft²).

Discussion of the genera of this species: Shrubby running bamboos, they contains the number of branches on the node are usually single branch, sometimes 2 branches is the most and small amount of 3 branches at the secondary branches, and the culm nodes are uplifted at the attachment of the sheath,  the ciliata on the shoulder disappear when mature, which are obviously incompatible with genus Sasa. The vegetative leaves of this species are huge, the culms are thin, and the plants are always short. In the habitat, they are mostly attached to the tall shrubs and are sparsely existing and unable to form a bamboo forest. It is far away from the genera: Arundinaria and Psedudosasa. Because the maximum height of this species is not taller than 2 meters, open type vascular bundles found from the the cross section of the culm. The floret of this species has greenish lemmas, yellowish-white stamens, 3 stamens, yellowish anthers, and inflorescences in panicles. In addition, morphological structure of the vegetative leaf  are also closely related to the genus Indocalamus, therefore, it is recommended to be included in of this category.

In order to respect the previous sages who studied this species, the author suggests to retain the original Chinese name (光笹竹) and add a descriptive name (香港箬竹) to supplement the sparseness.
　

Taxonomic position of  Indocalamus subglabra (McClure) Ng et al., 2021, genera rearrangement

 PHYLUM MAGNOLIOPHYTA
● Class Liliopsida
 ● Subclass: Commelinidae
  ● Order: Cyperales
   ● Family: Poaceae
    ● Supertribe: Arundinariatae
     ● Subtribe: Sasinae
      ● Genus: Indocalamus

Fig. I:  Indocalamus subglabra (McClure) Ng et al., 2021  (drawn by Cognitio Sapiens Ngensis)
1. portion of culm, 2. sheath proper, 3. blade, 4. cross section of culm, 5. leaf, 6. enlargement of partial vein , 7. Panicle flowering branchlet, 8. foret, 9. stamens, 10. pistil, 11. lodicule, 12. lemma, 13. palea

光笹竹(香港箬竹) Indocalamus subglabra (McClure) Ng et al., 2021, genera rearrangement,
Synonym: Sasa subglabra McClure, Lingnan University Science Bulletin, 9: 45 1940, Hong Kong Bamboos,  P.75, 1985,  Flora of China, V9(1): P.674, 1996,  Flora of Guangdong, V9: P.291, 2009, Flora of  Hong Kong, V4: P.142-143, 2011.
Digital images of holotype specimen examined: barcode 00141340, 00065443, topotype specimens: barcode 00305601~ 00305604, Coll. No. 21251, by H. Fung, 03 V 1938, US National Herbarium specimen, by Smithsonian Institution.
Voucher specimens: NSF-3581835, NSF-3581835(A)~(E), Acta Scientium Ngensis.
　

Fig. II:  Indocalamus subglabra (McClure) Ng et al., 2021 in wild

Fig. III:  Indocalamus subglabra (McClure) Ng et al., 2021 typical  A. vegetative leaf, B. Culm sheath, C. branches

Perennial, shrubby bamboo, culms erect, smoothly,  40cm~ 200cm tall, 5-1.5mm in diameter, lateral branches suffrutescent, branches usually 1(commonest, fig III: C) to 3 (rarely) at upper nodes (Fig II: A), internodes terete, always 10-20cm long. Culm nodes are uplifted at the attachment of the sheath (Fig II: B), Culm-sheaths persistent, minute ciliolate when young (Fig II: C), sheaths tightly culm clasping, without auricles when mature, Culm-sheath blade linear; erect (Fig II: D). Vegetative leaf (fig III: A) in grassy-grennish color, oval to oblong-lanceolate, 10-30cm long, 2-6cm wide, shorty ciliolate towards beneath, without auricles, 12-18 veins impressed adaxially and prominent abaxially, mid-viens are particularly wide and obvious. Rhizomes (Fig II: F) elongated, sympodium.

Fig. IV: Indocalamus subglabra (McClure) Ng et al., 2021 , flowering branchlet

Fig. V: Indocalamus subglabra (McClure) Ng et al., 2021 , anatomical view of a floret

Lateral panicles (Fig IV: A~D), dense arranged, ranging from 4 to 10 cm in length, floret 8-12 mm long, lemma (picture IV: C) grassy-greenish in color, 10 mm high when mature, palea (Fig IV: D) Yellowishish-white, 75 mm high when mature, lodicule (Fig. V: E) lanceolate, silvery white, average 1.3 to 2 mm in height , pistil with 3 stigma (Fig. V: B), about 3 mm long, white , Purple-black when mature, 3 stamens (Fig. V: A), 3 to 4 mm long, 0.5 to 1 mm wide, yellowish-green when immature, and orange-yellow when mature. The ovary is underdeveloped; the florets in the withered inflorescence are aborted, the seeds: not seen.

Acknowledgment

The flowering of bamboo is a relatively rare phenomenon. Because of the different species, the flowering period can exceed a century, and then the next flowering period will be ushered in. For this species, no one cannot predict its next flowering period, we hope this population to be able to bloom again, they can survive the challenge of survival and keep on living in Hong Kong.

We wish to express our the deepest gratitude to Professor Floyd Alonzo McClure (1894-1970).

References
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