ISSN 0308--0838 THE FERN GAZETTE VOLUME TWELVE PART THREE 1981 THE JOURNAL OF THE BRITISH PTERIDOLOGICAL SOCIETY THE FERN GAZETTE VOLUME 12 PA RT 3 1981 CONTENTS Page MAIN ARTICLES Drought tolerance in Cheilanthes with special reference to the gamatophyte - H. Quick & T.C. Chambers 121 Tropism• in Regne/lidium diphyllum-L.D. Gomez 131 An ecological survey of the Ferns of Berwickshire, Scotland-A. Wi/lmott 133 Cheilanthes coriacea. An Afro-Arabian species new to Iran- C.R. Fraser-Jenkins 155 A chromosome count for Asplenium anceps from the Canary Islands -H. Rasbach. K. Rasbach & J.J. Schneller 157 A chromosome count for Macrogolossum (Marattialas)- T.G. Walker 161 An analysis of The Grammitis poeppigiana-G. magellanica �omplax in the South Atlantic and South Indian oceans- B.S. Parris 165 Two new species of Selaginella from the Phillipines- B.C. Tan & A.C. Jermy 169 A forked vain and foliar fibres in Selaginella- R.N. Mukherjee & U. Sen 175 SHORT NOTES Dryopteris x sarvelae in Scotland; a new hybrid for the British Isles - H. V. Corley & M. Gibby 178 A new name for a hybrid horsetail in Scotland- C. N. Page 178 Equisetum x trachyodon in Skye, Western Scotland -C. W. Murray 179 More new combinations in Southeast Asian Ferns- B.S. Parris 180 The occurrence of a lamina! flap in Selagine/la -R. Mukhopadhyay & U. Sen 180 A new species of Plagiogyria from Malaya- R.D. Dixit & A. Das 182 Nomenclature notes on Dryopteris - C.R. Fraser-Jenkins 183 REVIEWS 130, 160, 164, 174 (THE FERN GAZETIE Volume 12 Part 2 was published in 1980) Published by THE BRITISH PTERIDOLOGICAL SOCIETY, c/o Department of Botany, British Museum (Natural History), London SW7 5BD. METLOC PRINTERS LTD · Old Station Road · Loughton · Essex FERN GAZ. 12(3) 1981 121 DROUGHT TOLERANCE IN CHEILANTHES WITH SPECIAL REFERENCE TO THE GAMETOPHYTE HELEN QUIRK & T. C. CHAMBERS Botany School, University of Melbourne, Parkville, Victoria, Australia. ABSTRACT The gametophytes of a range of Australian species of Cheilanrhes are shown, in comparison with other more mes1c genera of ferns, to have the remarkable capacity to withstand severe water deficits and survive after drying and continued exposure to periods of low humidity. This ability to withstand severe desiccation is considered to be important in the establishment and survival of the genus in ecological niches not otherwise colonized by ferns. INTRODUCTION Only a few genera of ferns are noted for their drought tolerance and their ability to survive in habitats usually not colonized by pteridophytes. Some genera are able to survive over extensive areas of open country otherwise hostile to most species of ferns. The almost cosmopolitan Pteridium is a good example of such a species as is Paesia scaberula in New Zealand. Such plants have become serious weeds of pasture country. To what extent the invasion by these species is associated with the biological adaptation of the gametophyte as against the adaptations of the rhizome of the sporophyte is not fully understood. Only a few of the genera of the lower vascular plants are able to extend into much more arid habitats than are these two examples; PeJiaea and Cheilanthes are notable examples from the Leptosporangiate ferns; the resurrection plants Selaginella lepidophyl/a and S. rupestris are well known examples · from the Lycopsida. In Australia we have observed that the sporophyte of some species of Cheilanthes perennates during the summer months by means of a rhizome while the fronds completely die down e.g. C. tenuifolia and C. sieberi. Other species which extend even further into the arid parts of Australia maintain at least a few of their leaves in an extremely dehydrated but living state e.g. C. vel/ea and C. lasiophylla. There are a few species of Cheilanthes which grow in the cooler coastal regions of Australia. But even in these regions they are never found in the moist, sheltered, constantly humid environments of most other ferns but rather they prefer rock crevices and shallow soil pockets in dry rocky hillsides e.g. C. distans. These species in these habitats sometimes perennate in the hot summer months by means of their rhizome, but under less severe conditions they may remain with some green fronds ' throughout the growing season. Hevly (1963) has described several adaptations of cheilanthoid fern genera of Arizona to their harsh desert environments. Many of these features are certainly also characteristic of the Australian species of Cheilanthes in their sporophytic state. The sporophytic stages of Australian species exhibit • microphylly .and some have a dense indument of hairs and/or scales; the plants are small (generally below 30 cm in height) and either have narrow fronds (C. sieben: C. lasiophylla) or if with ovate fronds then these are finely dissected (C. tenuifolia) or they may have very narrow pinnules (C. caudata). Hevly suggests that the dissection is a reduction in leaf size which may reduce water loss by reduction of tota l leaf surface. The rhizomes of all species of Cheilanthes in Australia are densely scaly and a cover of hairs and/or scales is found on the stipe and lamina of C. lasiophylla, C distans. C. vel/ea. C. hirsuta. C. contigua and an as yet undescribed sub-species of C. sieberi. That this thick indument is an inbuilt genetic feature of the plant is demonstrated in the observation that species of C. lasiophylla and C. distans taken from the field and 122 FERN GAZETIE VOLUME 1 2 PART 3 ( 1981) grown under glasshouse conditions protected from harsh light and severe water stress. show no lessening in the thickness of the scale cover on the new fronds which developed, even after more than a year in cultivation. Also, sporophytic plants of some of these species raised from gametophytes in cultivation showed the same thick scale covering as did their wild parents. lt seems likely that these scales and hairs may reduce water loss through transpiration by creating still air zones near to the plant surface in which the air remains at a relatively high humidity and t�ro-ugh which diffusion from the interior of the plant to the exterior would be slow. lt is also possible that the scales and ha irs reflect significant amounts of solar radiation especially in species growing exposed on desert rocks, e.g. C. vel/ea and C. /asiophyl/a. Certainly those species which genetically have the most dense indument (C. lasiophylla, C. vel/ea) are found in the more arid regions of Australia. However, the more common form of C. sieberi is unusual in having a glabrous stipe and lamina and yet it is often found growing in the same arid localities as C. lasiophylla. Leaves of the Mediterranean cheilanthoid fern Notholaena marantae R.Br. were reported by lljin (1931) to tolerate desiccation to relative humidities of less than 50%. This tolerance was attributed to the low leaf surface-to-volume ratio which lljin suggested reduced the change in volume of the cells on de- and rehydration. In addition he reported the presence of a non-drying substance in the cells, a stable body or "fester Korper" which could be differentially stained from the cytoplasm. The fronds of the Australian C. sieben: C. tenuifolia, and C. "austrotenuifo/ia"* wilt and die under hot conditions and low humidity. On rehydration, after a sustained dry period, completely new fronds are produced from the rhizome. This seasonal drying off may be at least partly a response to high summer temperatures and longer day length rather than summer water deficit. Evidence supporting this view is obtained from glasshouse-grown specimens of this species which die off each summer despite regular watering and sprout new fronds from the rhizome in autumn. On the other hand, C. lasiophyl/a in cultivation tends to die off to a lesser extent when glasshouse grown and it also does not normally produce new shoot� during the hot months even if watering is maintained. We have obtained the best growth responses of these plants in cultivation by ensuring that they are subject to some water stress during the hot summer months. lt can be seen therefore, that there are a number of adaptations of the sporophyte of Australian species of Cheilanthes which include both stress avoidance (by reduction of moisture loss) and high temperature tolerance as seen by the ability to regenerate new fronds after what appears superficially to be death of the old plant by drought. However, these adaptations for many habitats in which these species occur would be in vain if the spores and the gametophyte generation were not also able to avoid or endure periodic xeric conditions. Such adaptations of the gametophyte could range from simple drought avoidance by rapid growth and maturation leading to early establishment of the sporophyte to either, morphologically distinctive xeromorphic features reducing water loss from the gametophyte or to truly physiological xerophytic adaptations of a cytoplasm which can withstand periodic desiccation. Spores of Cheilanthes appear to be tolerant of extreme and prolonged exposure to low humidity. Working with the North American species C. gracillima, D.C. Eaton, Pickett (1923) reported that the spores remained viable after a period of 16 months over anhydrous calcium chloride even though the cytoplasm by this time appeared "dried and shrunken to the sides of the spore". Although we have not made a *The name "austrotenuifolia" has no status. lt is used to designate populations of a species morphologically very similar to C. tenuifolia and up to the present referred to that species but with most distinctive spores. lt is widely distributed through the southern half of the Australian continent and we are presently investigating its correct name.