CYTO-TAXONOMIC STUDIES ON NEW ZEALAND PTERIDACEAE BY G. BROWNLIE Botany Department, Canterbury U?iiversity College {Received 15 Jttne 1956) (With Plates 4 and 5) These studies are being undertaken in the hope that they may contribute to concepts on the interrelationships of the various fern groups. Detailed examinations of fern floras of Northern Hemisphere areas have been reported by Manton (1950) and Britton (1953), and of one tropical island by Manton and Sledge (1954). A similar treatment of a Southern Hemisphere area should prove of particular interest. New Zealand is well placed for such a study in the light of the theory of the Antarctic origin of most of the tropical fern flora, with the most primitive representatives of many groups still as near as possible to that source (Copeland, 1947). The terminology used is that of Dobbie (1951) based on Copeland's taxonomic system. MATERIALS AND METHODS Chromosome counts have been based completely on aceto-carmine preparations of suitable-stage sporangial material previously fixed in i :3 acetic alcohol. Such fixed material has been used, for the species described, up to ten days after fixation. For most of the species mentioned use was made of both wild and cultivated specimens. OBSERVATIONS DICKSONIA (Plate 4, Figs, i and 6) This genus is represented in New Zealand by three species, two of which have been cytologically examined. Bicksoriia squarrosa Swartz and Dicksonia fibrosa Col. are both medium-sized tree ferns abundant in rain-forest areas in many parts of the country. Examination of both wild and cultivated specimens over a period of two growing seasons has given a consistent count of n = 65. This is closest in number to the Ceylon species of Dennstaedtia described by Manton and Sledge (1954). It is interesting to note that Copeland (1947) regards Dicksonia as a relict genus and Dennstaedtia as a base genus for several lines of development within the Pteridaceae. LINDSAEA (Plate 4, Fig. 3) Lindsaea ciineata (Forst. f.) C. Christen was the only species of this genus examined, and unfortunately only a small amount of material was available. Counts of n = 42 and 43 were obtained thus showing a possible link with Lindsaea caudata Hk. which yielded n = 82. HYPOLEPis (Plate 4, Figs. 5 and 7) In this genus both the chromosomes and the sori are small, making good preparations and accurate counting diflicult. After examination of material from the two species 207
2o8 G. BROWNLIE described it is felt that the results are reasonably accurate. Hypolepis rugosula (Labill.) J. Smith gave n = 52 and Hvpolepis teuuifolia (Forst. f.) Bernh. n = 104 showing a probable connection with Pteridium. PTERiDiUM (Plate 4, Fig. 2) The one native species Pteridium esculentum (Forst. f.) Diels {Pteridium aquilinuni var. esculentum) gave the same count of n = 52 as the European Pteridium aqitilinum (L.) Kuhn (Manton, 1950) and the North American Pteridium aquilinuni var. latiusculmn (Desr.) Underw. (Britton, 1953). PAESIA (Plate 4, Fig. 4) This genus is another which appears to be related cytologically to Pteridium, the single species Paesia scaberitla (A. Rich.) Kuhn giving n = 26. It does, however, suggest a possible lower base number for this section of the family, than the previously presumed lower 50s (Manton and Sledge, 1954). PTERis (Plate 5, Fig. 8) Although several species of this genus occur in New Zealand only one of these has been examined fully. Pteris tremitla R. Br. gave a count of n = approximately 120, a figure completely in accord for other observations on this genus. CHEILANTHES (Plate 5, Fig. 9) The single local species accurately counted, Cheilanthes sieberi Kunze has been observed to develop sporophytes directly from gametophytic tissue in every case. The triploid (n = 87) and apogamous conditions are assumed from the number given by Manton and Sledge as n = 29 for presumed diploid forms of Cheilanthes. Although the chromosomes are fairly large, difficulty was found in this species in obtaining good spreading. PELLAEA (Plate 5, Fig. 10) Pellaea rotundifolia (Forst. f.) Hook, appears to be the only member of this genus so far recorded that is a simple diploid. The count of n = 58 compares closely with those of Manton (1950) who recorded an apogamous species with n = 87, and Britton (1953) who examined a tetraploid with n = 116. ADIANTUM (Plate 5, Fig. 11) Adiantum hispidulum Sw. appears to be based on 29 rather than 30, a fact noted by Manton and Sledge (1954). Although a large number of figures of this species were examined the highest count obtained was n = 173, and the figure illustrated shows 170 clearly. DISCUSSION Any paper discussing taxonomic problems from one angle must emphasize the fact that the evidence produced is only additional to previous knowledge. For this reason cytological examination of the ferns is carried out in the hope that it may clarify some of the uncertainties in relationships theorized in current taxonomic systems. It must be admitted that the results shown in the present work tend merely to emphasize the divisions noted in Copeland's Pteridaceae by Manton and Sledge (1954). With the addition oi Paesia the group noted by those authors as 50 to 52 can probably be based in the middle 20s. Similarly the figure of 42-3 noted for Lindsaea cuneata supports their grouping in the middle 40s. Dicksonia appears to be most nearly related to the Dennstaedtia section. The
THE NEW PHYTOLOGIST 56, 2 PLATE 4 # #' ' 0 % I BROWNLIECYTO-TAXONOMIC STUDIES ON NEW ZEALAND PTERIDACEAE (Facing p. 208)
THE NEW PHYTOLOGLST, 56, 2 PLATE 5. * «0 ^ V?^3. 10 BROWNLIECYTO-TAXON(JM1C STUDIES ON NEW ZEALAND PTERIDACEAE
Cyto-taxonomic studies on New Zealand Pteridaceae 209 remaining genera examined Pteris, Cheilantkes, Pellaea and Adiantu?n are all based on 29 or 30, so that support is given to the major discontinuity noted by Manton and Sledge (1954). It must be conceded, however, that a much wider examination of other genera in Copeland's Pteridaceae is required before any action to split the family can be taken. SUMMARY Table i summarizes the published gametic chromosome number for the genera of Pteridaceae discussed. Dicksonia Lindsaea Hypolepis Pteridium Paesia Pteris Cheitanthes Pellaea Adiantum Table i. Meiotic chromosome nttmbers in Pteridaceae Manton 50, 100, 150 82 51-3, 100 52 29,58, 90, 120 29, 58, 87 30, 87;'^ 90 29, 58, 170-80 30, 60, 90 Gametic chromosome numbers Author Britton Brownlie 5-116 29 30 65 42-3 52, 104 52 26 I am indebted to the Research Committee of the University of New Zealand for a travelling grant for the purpose of collecting material for this research. I wish also to thank Professor L Manton of Leeds for her suggestions on this line of investigation. 120 87 58 174 REFERENCES BRITTON, D. M. (1953)- Chromosome studies on ferns. Amer. y. Bot., 40, 575- CHEESEMAN, T. F. (1925). Manual of the New Zealand Ftora. 2nd ed. Govt. Printer, Wellington. CoPELAND, E. B. (1947). Genera Filicum. Waltham, Mass. DoBBiE, H. B. (1951). New Zealand Ferns. 4th ed. Revised by Marguerite Crookes. MANTON, I. (1950). Problems of Cytology and Evolution in the Pteridophyta. Cambridge. MANTON, I. & SLEDGE, W. A. (1954). Observations on the eytology and taxonomy of the pteridophyte flora of Ceylon. P/j/Zoi. Tram."B, 238, 127. PLATE 4 Meiotic preparations, photographed, x 1000 Fig. I. Dicksonia squarrosa Sw. n = 65. Diakinesis. Fig. 2. Pteridium esculentum (Forst. f.) Diels. n = 52. Late diakinesis. Fig. 3. Lindsaea cuneata (Forst. f.) C. Christen. n = 42-3. Diakinesis. Fig. 4. Paesia scaberula (A. Rich.) Kuhn. n = 26. Diakinesis. Fig. 5. Hypotepis rugosula (Labill) J. Smith, n = 52. Late diakinesis. Fig. 6. Dicksonia fibrosa Col. n = 65. Diakinesis. Fig. 7. Hvpolepis tenuifoua (Forst. f.) Bernh. n = 104. Late diakinesis LEGENDS TO PLATES PLATE 5 Meiotic preparations, photographed. X 1000 Fig. 8. Pteris tremula R.Br. n = 120. First meiotic metaphase. Fig. 9. Clieilanthes sieberi Kunze n = 87. First meiotic metaphase. Fig. 10. Pellaea rotundifotia (Forst. f.) Hook, n = 58. Diakinesis. Fig. II. Adiantum hispididum Sw. n = approx. 174. First tneiotic inetaphase.