Studies of diagnostic features in the genus Hypoxis L. (Hypoxidaceae R. Br.) on the Witwatersrand

In an attempt to clarify specific concepts in the genus Hypoxis L. on the Witwatersrand it was found that diagnosis depends mostly on vegetative characters, particularly the habit, leaf vesture and venation, and the structure of the inflorescences. The relevant criteria are discussed in relationship to the Witwatersrand species, where eleven species and seven varieties are recognized: H. rigidula Bak. (a) var. rigidula, (b) var. pilosissima Bak.; H. acuminata Bak.; H. filiformis Bak.; H. obtusa Burch.; H. neliana Schinz; //. latifolia Hook. f.; H. galpinii Bak.; H. multiceps Buch. ex Bak.; H. interjecta Nel; H. rooperi MoOre; H. argentea Harv. ex Bak. (a) var. argentea, (b) var. sericea Bak.; and two varieties which constitute comb, et stat. novs, unpublished as yet.


INTRODUCTION
Hypoxis L. is the type genus of the small family Hypoxidaceae R.Br. with distribution in the warmer regions of all the continents except Europe. In southern Africa it is well represented in the summer rainfall area, but absent in the flora of the Western Cape.
Quite recently (Walford, 1978), medical interest has arisen in certain Hypoxis species which were found to yield compounds useful in treatment of prostate cancer and of rheumatism. Further research is going on.
The genus was comprehensively treated by Baker (1878), and Baker's descriptions of the South African species were included in Flora Capensis (1896). The family was revised by Nel (1914). A partial revision of the Natal species has been recently carried out by Wood (1976, unpub.).
My studies were concerned with an attempt to clarify the specific determinations in the genus on the Witwatersrand. Here, for a few weeks in spring, Hypoxis is a dominant element in grassland; however, little is known about the genus. Before any taxonomic treatment, I had to gain information on population structures, life cycles, morphology and anatomy of the taxa. Then I was able to correlate these data with the accepted nomenclature available in literature and herbarium collections. In the present paper I want to discuss some of my findings.
It soon became evident that in this genus diagnosis at specific level depends mostly on vegetative characters. The habit, leaf vesture and anatomy, and the structure of the inflorescences yield the most important criteria.

Gross morphology
The plants have a simple 'streamlined' appearan ce: a perennial corm with contractile roots and an annual complement of basal leaves and slender unbranched axillary peduncles. The leaves and peduncles emerge trifariously (1/3 phyllotaxis) from the corm apex. 2.1.1 Rootstock. Hypoxis corms generally do not form offsets. They grow vertically upwards, conti nuously pulled deep into the ground by their contractile roots. Above ground there is a single shoot.
In two Witwatersrand species, H. acuminata (Fig.  1A) and H. galpinii, the rootstock after a time spreads horizontally, forming short stolons. Each has a cormlike structure with a shoot at the apex. Above ground arises a tussock of several shoots, often as many as 20-40.
2.1.2 Habit. The length of mature shoots covers a range from 80-1400 mm. Three groups can be distinguished.
(a) Shoots spreading trifariously from the base. Here belong species with falcate leaves tightly stacked above each other in three ranks at angles of 120°: the large H. rooperi (Fig. IB) 1C).
(b) Leaves emerge from the ground in a trigonal leaf column sheathed by cataphyll bases so that a pseudostem is formed (Fig. ID).
The pseudostems are as wide in diameter as the emerging leaves in H. rigidula, the tallest species in the genus, with pseudostems up to 200 mm long; the medium sized H. acuminata and the small H. filiformis in which the pseudostem is often absent.
In H. neliana the pseudostem is wider than the leaves, though it is only 10-20 mm long.
(c) Funnel shaped shoots. Leaves grow vertically upwards, only slightly separating from each other so that the shoot is wider above, in the shape of a funnel. In H. latifolia, a large species with leaves widest in the genus, leaves reach 100 mm in width.
In the medium sized H. galpinii (Fig. IE) the leaves when mature are connivent on the top.
In H. multiceps (Fig. IF) and H. interjecta towards end of the season leaf bases narrow down and form pseudopetioles. The narrow pseudope tioles at the base and the wide laminae above produce a funnel effect.

Vesture (Fig. 2 A,C)
One of the basic characters of the genus is the presence of hair on all the aerial parts of the taxa. The trichomes are unicellular, but pluriseriate (Hummel & Staesche, 1962). That means that a single foot-cell in the epidermis may carry one simple hair, or one two-armed hair, or a stellate hair with 3-6 arms, or hair fascicled, with up to 18 arms.  (Fig. 3) 2.4.1 Veins in transection. The leaves of Hypoxis have parallel veins of uneven thickness, some very prominent. In transection they are seen as strands or girders (Metcalfe, 1960). The strands are small bundles of vascular tissue, surrounded by a bundle sheath. In girders the circumvascular sclerenchyma extends across the width of the lamina to the epidermis.

Colour
There is little interspecific variation in colour. In nearly all the taxa the corms exude yellow mucilage when sectioned; the aerial parts are green and dry beige-brown; the flowers are yellow.
However, there are solitary exceptions. The corms of H. argentea are white in section; the peduncles and pedicels in this species are tinged maroon. H. rigidula var. hemerocallidea has purple pseudostems. When dried H. galpinii leaves turn red, and in H. obtusa var. obtusa the dried foliage is silvery grey. H. filiformis at times produces whitish flowers.