African Biosciences Network and the United Nations University Bethesda, Maryland, USA.

INTRODUCTION
As space travel and genetic manipulation open new vistas to mankind, tropical forests still presnt an intriguing diversity of species that defy comprehension. Our lack of knowledge and understanding of this luxuriant and other vegetation types is a telling commentary on our sense of [priority. The continuous elimination of some 11 million hectares of forest a year is depriving the world of many assets and options for solving some of the current and future problems of mankind. These include the search for new medicines, drugs, food plants, insecticides, essential and industrial oils and horticultural species. In fact since the discovery about 45 years ago of the so-called "wonder drugs" which are mostly of plant origin, pharmaceutical industries have been looking to the vast numbers of purported medicinal olants for new natural sources of drugs as starting materials. But the rate of current desctruction of the floristic elements in the tropics is likely to rob the world of potentially new sources of "wonder drugs" that will be needed during the rest of this century and certainly during the 21st century (Ayensu, 1983b).
India unquestionable occupies a premier position in the use of herbal drugs, utilizing nearly 540 plant species in different formulations (Kapoor and Mitra, 1979). For centuries a great majority of India’s population has depended on crude drugs and drug extracts for the treatment of various ailments. In fact India was one of the pioneers in the development and practice of well-documented indigenous systems of medicine, the most notable being Ayurveda and Unani. The materia medica of these systems contains a rich heritate og indigenous herbal practices that have helped to sustain the health of most rural prople of India. Today about 75% of the population consult mainly traditional and the sales turnover of indigenous medicines is about one and a half times that of modern drugs (Rustogi, 1980)..
The first three indian orchids discussed below are of potential or actual use of traditional medicine and at present endangered or vulnerable (Lucas and Synge, 1978).
Paphiopedilum druryi is natie to Kerala but is endangered or extinct in the wild due to forest fires and excessive collecting. There are indications of its use in ayurvedic medicine and it may have useful alkaloids. Though known in cultivation around the world, only about a dozen individuals are being grown in India. Various authorities have indicated its decline in the wild state (U.C. Pradhan 1975, 1976, 1977); Mammen and Mammen, 1974). Dendrobium pauciflorum is endangered, possibly extinct, and known from West Bengal and Sikkim in areas open to tree-felling. It may likely be found to have alkaloids of potential value < if rediscovered in the wild. Its precarious situation has been noted by Pradhan (1975, 1976, 1977). Diplomeris hirsuta, which possibly contains useful alkaloids in the tubers, is restricted to a few numbers in West Bengal in a region vulnerable to landslides. Its decrease in numbes has been pointed out by G.M. Pradhan (1976); U.C. Pradhan (1975, 1976, 1977), Kataki (1976), and Varmah and Sahni (1976).
Another species, Dendrobium nobile, deserves mention. Occurring in the Himalayan regions of India and China, it is a source of dendrobine, a principal alkaloid, and is exported from China by the ton in a dehydrated condition (Pempahishey, 1974). The Indian National Orchidarium at Shillong has brought approximately 350 indigenous orchid species into cultivation for conservation puroses.
Various endangered and threatened plants that have been indicated as of potential or actual use in traditional medicine are listed in Table 1.
There are a few examples of sought-after plants which deserve special mention. Dioscorea beltoidea has been much sought after by private agencies and pharmaceutical firms, having been continuously collected in India, except perhaps in the more inaccessible areas of the Himalayas (Santapau, 1970; Qureshi and Kaul, 1970). Its natural range includes parts of Afghanisthan, Pakistan, India, Nepal, Bhutan, China and Vietnam. The roots yield cortisone, a steroidal hormone used in treating rheumatic diseases and ophthalmic disorders. The plant is cultivated in Punjab and kashmir for the edible roots. Investigations of its genetic variability are being undertaken by the Regional Laboratory in Jammu Tawi, India (Sobti et. al., 1980); and tissue cultures are under way in Calcutta (Mitra, 1980).
An examination of the ancient systems of Ayurveda and Unani will indicate the Rauvolfia serpentina was well known and in use by medicine men of India, Sri Lanka, Nepal, Burma and other oriental countries for the treatment of insanity. This is possibly associated with hypertensive encephalopathy.
The first Western scientist who published the uses to which the plant was put in india was Garcia de Orta in 1563. Most European physicians were very sceptical of the purported properties of the plant. However, in 1952 the alkaloid reseprine was isolated, thus confirming the plant’s value. Since then the alkaloidal extract, as well as purified alkaloids of Rauvolfia serpentina, have become very important in the treatment and control of hypertension.
The administration of the extract bring about a lowering of the blood pressure in hypertensive states, lowering of the pulse, and exhibition of a general sense of euphoria. The alkaloids in the plant have been shown to be phenotropic, and to influence the functions of the mind and behaviour. It is no wonder that the medicine men of India consistently administered this plant to the insane. Today the plant is cultivated in commercial quantities in many parts of the world. notably India and Thailand.
According to Santapau (1970), before 1952 Rauvolfia serpentina was used in the indigenous system of medicine, but the demand was not great; the plant was common and abundant in forest areas all over peninsular India. However, after the publication of the various papers extolling the medicinal powes of the plant, a ruthless search was started all over the country, a search that only came to a halt when Rauvolfia was found to have disappeared from forest areas.
The species is now consistently indicated by varikous other authorities as becoming very rare in nature (Maheshwari 1970; Srinivasan, 1959; Sahni 1970; Qureshi and Kaul; 1970). when an important species such as this is over collected, there is always the potential for disappearance of important, discrete gene pools of intraspecific variation which may be useful in further research on the chemical properties of the entire generic composition of the species.
Two distinct ecotypes, i.e. basically subspecies that grow in different environments due to characteristics that are probably physiological but genetically controlled, have been recognized in R. serpentina, Various stocks from Kerala, Dehra Dun (Himalaya), Karnataka and Goa are being explored for reserpine and alkaloids at the national Bureau of Plant, Genetic Resources, New Delhi (Gupta and Mital, 1978). Thus we may hope to have more valuable data from wild variant populations of the sepcies before its decline to mere remnants of its original abundance.

WORLD MEDICINAL PLANT RESOURCES

Table 1 : Endangered plants of actual or potential use in traditional medicine*

The export of Saussurea lappa is restructed in Kashmir. The roots are utilized in a multitude of ways, among others as a tonic and carminative; as an antispasmodic in bronchial asthma, cough and cholera; and as an ointment for ulcers. They are also smoked as an optium substitute. The present scarcity of this valuable plant has been indicated by many (Maheshwari, 1970; Srinivasan, 1959; Sahni, 1970; Subramanyam and Sreemadhavan, 1970).
Acorus calamus, a Eurasian aroid known as vacha in India, were it is used in 51 different drug preparations, contains an essential oil in the rhizomes that possesses market insecticidal and sedative properties. Supplies of this plant in india and becoming scarcer (Maheshwari. 1970; Srinivasan, 1959). Apparently it used to be common in india in the north-eastern areas such as manipur and the Naga hills, yet it has been imported into Bombay from overseas for its medicinal aromatic rhizomes. Srinivasan (1959) has suggested that proper use of existing local Indian in the north-eastern areas such as Manipur and the naga Hills, yet it has been imported into Bombay from overseas for its medicinal aromatic rhizomes. Srinivasan (1959) has suggested that proper use of existing local Indian produce a Acorus, including measures to extrend the pant’s range in India, is desirable lest the local supply become disused or neglected.
A team at the Regional Research Laboratory (CSIR) in Jannu Tawi, India (Saxena et. al. 1977), has isolated a new insect chemosterilant from this species, with antigonadal functions specific enough to indicate that it may represent a new concept in insect chemosterilization. One can appreciate the value of maintaining local stocks of such important threatened species in case they should be required for independent local mass production at short notice.
Catharanthus coriaceus, a highly restructed endemic plant of Madagascar, where the flora as a whole is acutely threatened by grazing and burning, is the most endangered species in the genus Catharanthus (Lucas and Synge, 1978). Although no phytochemical research has yet bwen done on C. coriaceus, it is potentially important species since its close relative, the Madagascar periwinkle (C. roseus, which is phenomenally expensive, is a frequent component of chemotherapy programmes which have led to a significant decrease in mortality among young leukemia patients in the United States, and the compound ajmalicine is used in Europe for the treatment of heart diseases (Vietmeyer, 1979). This has led to decimation of natural population of C. roseus in areas around the world. Catharanthus coriaceus should obviously be conserved in Madagascar and investigated for its medical properties.

Interest of International Organizations
The recent revival of interest and respect for medicinal plants stems from a realization by such august bodies as the World Health Organization (WHO) (Penso, 1980), the Food and Agriculture Organization (FAO), the United Nations Industrial development Organization (UNIDO), etc., that nearly 90% of the world’s rural population has been kept in reasonable health due to an almost exclusive reliance on herbalists and traditional healers. Furthermore the WHO’s commitment to improve the health conditions of all peoples under their slogan "Health for All by the year 2000" has called for a serious assessment of the role that herbal medicine can play in the attainment of this noble objective.