PLANTS IN PERIL, 23 STACHYTARPHETA SELLOWIANA

Sandy Atkins, Ruy J.V. Alves and Jiri Kolbeck

Most tropical travellers interested in plants will have come across the pantropical weeds Stachytarpheta jamaicensis (L.) Vahl and S. cayennensis (Rich.) Vahl. These undistinguished plants, weeds of cultivated ground, obscure the fact that the genus contains some spectacular species well worthy of cultivation and with considerable ornamental merit.

Stachytarpheta Vahl is a genus of about 100 species widely dis- tributed in subtropical and tropical America, with a few in tropical Asia, Africa and Oceania. I t is a member of the Verbenaceae, with opposite leaves and flowers arranged in a terminal spike. In Brazil, there are some 40 species with their centre of diversity in the floristically rich areas of campos rupestres which stretch through the states o€ Minas Gerais, Bahia and GoiAs. Within these areas the genus takes on many forms. There is a very delicate annual herb, S. macedoi Mokdenke from Bahia which has bright purple corollas and there are sub-shrubs such as S. candida Mokdenke from GoiLs which trail along the ground with only their long spikes standing up erect, with white to palest pink flowers. Most species are erect shrubs or sub-shrubs growing to 3 m high, with leaves ranging from bright glossy green and almost succulent as in S. crasszfolia Schrad. , to those which are covered with fine long silky white hairs as in S. sericea S. Atkins. This last species combines a silvery appearance with a corolla which is almost black. Two closely related species from GoiAs are S. chamissonis Walp. and S. gesnerioides Cham. Both are robust tall woody sub-shrubs with spikes to 36 cm long, the former with a salmon pink corolla projecting from a bright green calyx with purple tips, the latter with a bright cobalt blue corolla and a yellow throat.

Most of the camPo rupestre species found in Brazil are restricted to quite small ranges; there has been little work on their pollination and seed production. Of the 35 species described by Schauer for Martius’ Flora Brasiliensis in 1851, a number have rarely been collected since. Stachytarpheta sellowiana Schauer has been found in only one locality, and even there it is apparently extremely rare. The only specimen at Kew, other than the recent collection made by one of the authors, is the type specimen collected by Sellow sometime between 1818 and

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Stachytarpheta sellowiana. A, habit, X %; B, corolla, X 2. Drawn by Mark Fothergill from the type specimen collected in Brazil in 181%1820 by Friedrich Sellow.

1820, and the only known locality is that recorded by him in the S5o Jos6 Range in the state of Minas Gerais. The state cited in Flora Brasiliensis is S5o Paulo, but we believe this to be incorrect. Friedrich Sellow was a German botanist, born in 1789 in Potsdam, who made three journeys through Brazil from 1814 to 1831. He collected extensively, and his journeys are written up by Ignatz Urban in Flora Brasiliensis (Urban in Martius, 1906). I t seems, however, that some mistakes were made in the exact localities or states of certain of his collections (Herter & Rambo, 1953).

Stachytarpheta sellowiana is a sub-shrub to 80 cm. The stems are 4- angled, covered with short hairs, some of them glandular. The leaves are densely arranged on the upper part of the stem, with their upper surface covered with short glandular hairs. The terminal spike of

@Bcntham-Moxon Trusi 1996, 34

flowers is short, with a persistent axis which is later overtopped by the new season’s shoots arising laterally, as can be seen in the drawing. The tubular calyx is 2 cm long; the corolla is bright blue and 3 cm long, each lobe being c. 1 cm across. The fruit of Stachytarpheta is a dry schizocarp which splits longitudinally into two 1 -seeded mericarps.

On a recent trip to Minas Gerais, Ruy Alves collected specimens and seeds ofS. sellowiana. He found only 20 plants in the type locality and none in neighbouring ranges despite searches. These were all mature plants with an average stem height (up to the first branch) of about 47 cm; no juvenile plants were seen. The visiting insects were recorded (all species of bee) and found to be Eulema nigrs’ta, Bombus spp. and Euglossa sp. Thirty inflorescences were picked for seed extraction but only 28 potentially viable and six aborted mericarps, in pairs, were found; slightly less than half the in- florescences had developed fruit. The collected seeds were dis- tributed to botanic gardens including the Micropropagation Unit of the Royal Botanic Gardens, Kew and the good news is that they germinated and the first flowering of these cultivated plants of S. sellowiana took place during 1995.

The area where this plant is found in the wild is often subjected to devastating fires but many plants, including S. sellowiana, appear to have adapted to a pyrophytic life-style. The Stachytarpheta has a large tuber-like root which immediately bursts into new growth after the fire. It is possible that the seeds also need to be subjected to fierce heat before germination can occur, although we have no definite evidence for this.

It is hoped that the survival of this rare plant may be secured through propagation and distribution by botanic gardens, but it is important, too, that the habitats containing such rarities are conserved.

REFERENCES

Herter, W.G. & Rambo, S.J. (1953). Nas pegadas dos naturalistas Sellow e

Urban, I . (1906). Vitae Itineraque Collectorum Botanicorum. In Saint-Hilaire. Revista Sudamericana de Botanica 10, 3: 61-98.

Martius, C.F.P. (1906), Flora Brasiliemis 1 , 1 : 105-1 1 1 .

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