n Si.. 2 3 /Q. 3 c '2 Memoirs of The Torrey Botanical Club Volume 23 Number 3 January 1977 Editor Robert W. Kiger THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Walter V. Brown LIBRARY may 25 197? NEW YORK botanical garden Memoirs of The Torrey Botanical Club Volume 23 Number 31 January 1977 Manuscripts intended for the Memoirs and related editorial correspondence should be sent to Dr. Robert W. Kiger, Hunt Institute for Botanical Documenta¬ tion, Camegie-Mellon University, Pittsburgh, Penn¬ sylvania 15213. Manuscripts should be double-spaced throughout and follow the style in the most recent issue of the Memoirs; an original and two copies should be submitted. Subscriptions, advertisements, and claims for missing numbers should be addressed to Dr. Gary L. Smith, New York Botanical Garden, Bronx, New York 10458. Requests for back numbers should be sent to Walter J. Johnson, Inc., Ill Fifth Avenue, New York, New York 10003. Published for the Club by Fisher-Harrison Corporation Seeman Printery Division Durham. N. C. 'Memoirs 23 (2), containing the paper by Robert R. Kowal entitled ‘‘Systematics of Senecio aureus and allied species on the Gaspe Peninsula, Quebec,” was published on August 22. 1975. THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Walter V. Brown Department of Botany, University of Texas, Austin , Texas 78712 CONTENTS Introduction . Materials and methods . Terminology and notation . The Paniceae . Panic um . The small tribes of the Panicoideae The Andropogoneae . The Danthonieae . The Aristideae . Eriachne . The Eragrostoideae . Miscellaneous grass taxa . Discussion . Acknowledgments . Literature cited . 1 1 1 12 12 32 53 60 63 66 71 72 79 81 91 91 LIST OF TEXT TABLES Tabic no. 1 . Photosynthetic and anatomical subtypes reported by others for Kranz species of the Gramineae. arranged by tribes and genera, 5. 2. C4 photosynthetic subtypes reported by others for a sedge and some dicotyledonous species, arranged by families, 7. 3. Species of Paniceae (less Panicnm) examined, arranged by genera: anatomical and photosynthetic charac¬ ters, provenances, and voucher herbaria; with new combinations under Steinchisma , 14. 4. Genera of Paniceae examined, arranged according to types of leaf anatomy and photosynthesis, 21. 5. Genera of Paniceae, arranged according to a modification of Hsu's (1965) scheme. 27. 6. Species of Panicnm examined, arranged alphabetically: anatomical and photosynthetic characters, prove¬ nances, and voucher herbaria, 33. 7. Species of Panicnm examined, arranged by supraspecific taxa; anatomical and photosynthetic characters, provenances, voucher herbaria, and basic chromosome numbers, if known, 40. 8. Supraspecific taxa of Panicnm, arranged according to types of leaf anatomy, photosynthesis, and fertile lemma surface, 52. 9. Species oft he small panicoid tribes examined, arranged by tribes and genera; anatomical and photosynthe¬ tic characters, provenances, and voucher herbaria, 54. 10. Genera of Andropogoneae examined for Kranz characters by various investigators, arranged alphabeti¬ cally, 61 . 1 1. Some shade-tolerant species of Microstegium (Andropogoneae), Setaria (Paniceae), and Muhlenherfjia (Sporoboleae): anatomical and photosynthetic characters, provenances, and voucher herbaria, 62. 12. Species of Danthonieae examined for Kranz characters by various investigators, arranged by genera: anatomical and photosynthetic characters, provenances and voucher herbaria, 64. 13. Species of Aristideae examined for Kranz characters by various investigators, arranged by genera and sections: anatomical and photosynthetic characters, provenances, and voucher herbaria, 67. 14. Comparison of various grass taxa by significant morphological, anatomical, and cytological characters, 70. 15. Species of Eriachne examined for Kranz characters by various investigators: anatomical and photosynthe¬ tic characters, and voucher herbaria, 71. 16. Genera of Eragrostoideae containing species reported as P.S. by others, arranged by tribes, 72. 17. Species of Eragrostoideae examined, arranged by tribes and genera: anatomical and photosynthetic characters, provenances, and voucher herbaria, 74. 18. Species of other grass tribes examined for kranz characters by various investigators, arranged by tribes and genera: anatomical and photosynthetic characters, provenances, and voucher herbaria, 79. LIST OF FIGURES Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Evolutionary scheme of the Paniceae, 29. Photomicrograph of a partial midrib cross section showing M.S. anatomy with a parenchyma sheath present in Panicum petersonii, 49. Evolutionary scheme of the Aristideae, 69. Evolutionary scheme of the Gramineae, 83. Evolutionary scheme of the Kranz syndrome in the Gramineae, 85. THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS' 1 2 The classification of the Gramineae based upon morphological (mostly spikelet) characters that developed dur¬ ing the 19th Century culminated in the treatments of Bentham and Hooker (1883) and Hackel (1887). This general system persisted during the first half of the 20th Century (Hitchcock, 1920, 1950; Stapf, 1920; Bews, 1929; and others). However, new characters were discov¬ ered starting in 1875 with the report by Duval-Jouve that there are two basic types of grass leaf anatomy. During the past hundred years numer¬ ous studies of grass leaf anatomy were published. Schwendener (1890) ex¬ amined the mestome sheath in numerous tax a. Holm (1890-1901) examined the leaf anatomy of many species in numer¬ ous tribes, and first reported the “dou¬ ble" parenchyma sheath condition in Aristida. Pee-Laby ( 1898) pointed out the concentration of chlorophyll in the parenchyma sheath cells. Lohauss ( 1905) studied general leaf anatomy and noted 1 This paper is dedicated to Joseph Duval-Jouve on the hundredth anniversary of his 1875 publica¬ tion reporting that there are two basic contrasting types of leaf anatomy within the grass family. Dur¬ ing the subsequent century numerous studies have confirmed his discovery, and recognition of these basic types has been instrumental in the develop¬ ment of new systematic treatments of the family. 2 Terms and notation used throughout are listed and defined under "Terminology and notation.” that some tribes, especially the classical Festuceae, contain among their genera both anatomical types. Avdulow (1931), however, first successfully utilized basic leaf anatomy (called "festucoid" or "panicoid") in an attempt to construct a better classification of the family. He also employed basic chromosome number, chromosome size, nucleolus characters, starch grain type, first seedling leaf characters, etc. as criteria. Hubbard (1948), Potztal (1952), de Wet (1956), Stebbins (1956), Brown ( 1958) and others continued the study of leaf anatomy in relation to the systematics of the Gramineae. Stebbins (1956) proposed four different leaf anatomical types and Brown (1958) recognized six. Between 1900 and the present, other non-morphological characters were dis¬ covered and applied to grass systematics. Prat (1932, 1936) studied the peculiar bicellular hairs and silica cells of the leaf epidermis and utilized their characters, along with those employed by Avdulow (1931), in an attempt at taxonomic clarifi¬ cation. He separated from the Festuceae and Agrostideae those genera having panicoid leaf anatomy. Tateoka, Inoue, and Kawano (1959), and Tateoka and Takagi (1967) have added data and quan¬ tified the subject of bicellular hairs, the presence or absence of which is now a major character in grass systematics. THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS 7 Reeder (1957, 1961, 1962), Decker (1964), and Tateoka (1969a) investigated the taxonomic application of embryo characteristics first revealed by van Tieghem (1897): vascular pattern, pres¬ ence or absence of a cleft between the coleoptile and coleorhiza, and width of the first true leaf. Embryo vasculariza¬ tion is now of major importance in grass systematics. Chromosome number and size have been significant in placement of many species and genera, and a few tribes. There has been some change from the conclusions of Avdulow, based on the increased importance accorded basic chromosome numbers (Tateoka, 1961a). Characters of lodicules (Stebbins, 1956; Tateoka, 1967; Hsu, 1965) and root hairs (Reeder and von Maltzahn, 1953; Row and Reeder, 1957), persistence of nucleoli (Brown and Emery, 1958), and many other non-morphological charac¬ ters have been found useful in grass sys¬ tematics. Stebbins (1956) discussed some of these newer characters and related them to systematics. Stebbins and Crampton (1961), Prat (1960), Metcalfe (1960), Jacques-Felix (1962), and Au- quier (1963) have listed and described most or all of them in considerable detail. Auquier listed a total of 67 characters of all sorts, some more significant than others, useful at various taxonomic levels. It is remarkable how these charac¬ ters are correlated. As a result, conclu¬ sions based upon one character can be tested by numerous others. Prat’s and Auquier’s reviews detailed these characters adequately and sum¬ marized knowledge of the subject up to 1963. They were published just at the time development of electron microscopy (Brown and Johnson, 1962; Johnson, 1964) and discovery of C4 photosynthesis (Kortschak, Hartt, and Burr, 1965; Hatch and Slack, 1966) stimulated a re¬ surgence of interest in leaf anatomy and its systematic significance. Subsequent investigations have revealed correlations between subtypes of C4 photosynthesis and subtypes of Kranz anatomy. In 1875, Duval-Jouve reported that there are two basic types of leaf anatomy among grass taxa. By 1920, these two sorts had been reported additionally in nine other angiosperm families. Occa¬ sionally these contrasting states were employed in systematics (Avdulow, 1931). In one state there are no specialized cells around the vascular bundles. That is the common type of leaf anatomy in angiosperms, now called non-Kranz. The other type, which is much less common, is usually charac¬ terized by a ring or wreath (in German, a “Kranz") of specialized cells around the vascular bundles. The latter was called the Kranz type by Haberlandt (1884). Thus, reference to Kranz cells specifies those of this unique sheath or tissue, and taxa characterized by such a tissue are referred to as Kranz species, genera, families, etc. (Brown, 1975). There are hundreds of Kranz species, in perhaps 200 genera, but only 12 Kranz families. The earliest method of characterizing plants as Kranz or non-Kranz was by ex¬ amination of stained mechanically cut or unstained freehand leaf cross sections. A second method was by observing the veins of whole leaves, living or dead, of such dicotyledons as A triplex (Moser, 1934). Such observation of non-Kranz di- MEMOIRS OF THE TORREY BOTANICAL CLUB 3 cotyledonous leaves by transmitted light at low magnification reveals a solid green or brown background and thin, usually translucent veins. If the leaf has Kranz veination (not “venation”), thick, dark, sheath-covered veins are observed, with small, irregularly-shaped, translucent spots among them. If a leaf is too thick to reveal the type of veination otherwise, boiling in water for about 30 seconds will make it obvious (Brown and Smith, 1974b). This is an excellent and quick method for screening large numbers of specimens. There are, of course, some dicotyledonous leaves that can be dif¬ ficult to classify by this method, such as narrow leaves or leaf lobes that have nearly parallel veins. Linear glands may produce an appearance like Kranz veina¬ tion. This method is unusable with grasses or sedges. Brown (1974) demonstrated that the M.S. subtype of Kranz anatomy, as de¬ termined from paradermal leaf sections, is almost always correlated with Kranz cells that are elongated parallel to the vein and are about twice as long as wide. In marked contrast, P.S. anatomy is corre¬ lated with Kranz cells oriented perpen¬ dicular to the vein and usually from twice as wide as long to about square. These correlations, which hold throughout the Panicoideae and Eragrostoideae, are made from paradermal views and enable a check of determinations made from cross sections. Often, paradermal views are critical to accurate determination. Hattersley and Watson (1975, 1976) re¬ cently examined many grass species for Kranz anatomical subtypes, employing their own symbolic representations. They demonstrated that all examined non-Kranz species have more than four (usually about seven) chlorophyll- containing mesophyll cells between adja¬ cent parenchyma sheaths, whereas all examined Kranz grass species have no more than two to four such mesophyll cells between adjacent Kranz cells. Their work updates that on the “intervascular interval” by Lommasson (1961) and the observations of Prat (1936), Takeda and Fukuyama (1971), and Kanai and Kashiwagi (1975), who also saw tax¬ onomic correlation with “interveinal dis¬ tance.” They considered this to be the best character for distinguishing between Kranz and non-Kranz in grasses, and I agree that it is at least as reliable as any other. For example, it indicates that the intermediates Panicum milioides and P. hians should be C3 species, which they are according to 813C ratios. This anatom¬ ical difference emphasizes that during, preceding, or following the evolution of the Kranz syndrome, additional intercal¬ ary veins have always evolved, possibly to increase the volume of Kranz tissue relative to mesophyll tissue and thus achieve a proper proportion for max¬ imum efficiency of C4 photosynthesis (see also the discussion of distinctive cells under “The small tribes of the Panicoideae”). In 1965, Kortschak, Hartt, and Burr, and, soon after, others (Hatch and Slack, 1966, 1970) discovered and characterized a new biochemical pathway of photo¬ synthetic C02 fixation which is called C4 photosynthesis. Almost immediately, C3 photosynthesis was related to non- Kranz anatomy and C4 to Kranz (Hatch, Slack, and Johnson, 1967; Downes and Hesketh, 1968; Downton and Tregunna, 4 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS 1968; Johnson and Hatch, 1968; Laetsch, 1968). Aside from some hybrids between Kranz and non-Kranz species of A triplex (Bjorkman, et al., 1971), Kranz anatomy has been reported for all plants charac¬ terized as C4 and non-Kranz for essen¬ tially all C3 plants. Therefore, C4 photo¬ synthesis must require Kranz anatomy without exception, though the crassula- cean acid metabolism (CAM) of some succulents is similarto C4 photosynthesis but is correlated with non-Kranz anatomy. There are a few taxa (Mollugo verticillata, Kennedy and Laetsch, 1974; Panicum milioides and P. hians, Brown and Brown, 1975; and a few plants of Alloteropsis semialata) which, essen¬ tially, have Kranz anatomy but C3 photo¬ synthesis. Although some of their photo¬ synthetic enzymes have intermediate ac¬ tivities, these are closer to C3 than C4 (Kanai, Ryuzi, and Kashiwagi, in press; Ku, Edwards, and Kanai, in press). Because there are a number of detecta¬ ble differences between C4 Kranz and C3 non-Kranz plants, the totality of charac¬ ter states unique and common to all C4 Kranz plants has been designated as the Kranz syndrome. Brown (1975) has proposed that the single, simple, unam¬ biguous term “Kranz" be used to include and imply all these anatomical and physiological characteristics of the syn¬ drome. Since the Kranz syndrome consists of a group of correlated characteristics, each distinct from the corresponding state in non-Kranz species, it follows, and has been demonstrated, that determination of any one of them predicts the presence of the others (Tregunna, et al., 1970; Laetsch, 1974). Each such characteristic is either necessary for C4 photosynthesis or else a result of that process. Biochemically, C4 species have much the same enzymes as C3 species, but in the former these enzymes may be sepa¬ rated, some in the mesophyll and others in the Kranz cells of the sheath. Further¬ more, the activities of certain photo¬ synthetic enzymes may be higher in either the mesophyll or Kranz tissue of C4 plants than in C3 plants. Notably, C4 plants possess the enzyme pyruvate P, dikinase not found generally in C3 plants. Simply stated, in C4 plants the C02 enters the leaf and is combined with phosphoenolpyruvate by the enzyme ph osphoenolpyruvate carboxylase (PEP-Case) to form, in the mesophyll, the 4-carbon molecule oxaloacetate. This is then converted, mostly to malate in the so-called malate formers and mostly (or entirely. Das and Rathnam, 1974) to as¬ partate in the aspartate formers. Malate or aspartate is then transported inward from the mesophyll cells to the Kranz cells through plasmodesmata in the cell walls. There the malate is decarboxylated by NADP-malic enzyme (NADP-me), or the aspartate (or derivative) is decar¬ boxylated by NAD-malic enzyme (NAD-me) or by PEP-carboxykinase enzyme (PEP-ck) (Edwards, Kanai, and Black, 1971), liberating a molecule of C02 and pyruvate. The C02, now in the Kranz cells, is incorporated into 3-phosphoglyceric acid by ribulose diphosphate carboxylase (Ru DP-Case) of the well-known Calvin-Benson cycle. The pyruvate (or alanine. Hatch, et al., 1975) returns to the mesophyll to pick up more C02. Thus, sugar and starch are formed mainly within the chloroplasts of MEMOIRS OF THE TORREY BOTANICAL CLUB 5 the Kranz cells, whereas in C3 species the starch is formed within mesophyll cells. The above Hatch-Slack biochemical cycle, which has three known variations for which corresponding biochemical pathways have been proposed (Hatch, Kagawa, and Craig, 1974), absolutely re¬ quires two distinct tissues: the mesophyll and the Kranz tissue. Therefore, all C4 plants must have Kranz anatomy , charac¬ terized at least by having a Kranz tissue internal to the mesophyll (Brown, 1975). Kranz cells have thicker walls (an appar¬ ent structural requirement) than do mesophyll cells, and these contain numerous pits and plasmodesmata. Biochemically, C4 photosynthesis can be detected (as it was originally) by de¬ termination that the first molecules con¬ taining the UC from 14C02 are of the 4-carbon types oxaloacetate, malate, and aspartate. This photosynthetic type, as well as its three subtypes, can also be determined by the relative activities of N ADP-me, NAD-me, and PEP-ck pres¬ ent (Gutierrez, Gracen, and Edwards, 1974; Hatch, et al., 1975). Tables 1 and 2 list most taxa known to have been charac¬ terized both enzymatically and anatomi¬ cally. TABLE I. Photosynthetic and anatomical subtypes reported by others for Kranz species of the Gramineae, arranged by tribes and genera. Phot. Anat. Author1 Phot. Anat. Author PAN ICEAE Axonopus Setaria compresses N ADP-me MS. 2 faberi NADP-me MS. 3 Brachiaria italica N ADP-me M.S. 3 brizantha PEP-ck PS. 2 lutescens NADP-me MS. 3 ciliatissima PEP-ck P.S. 2 verticillata NADP-me M.S. 3 dictyoneura PEP-ck PS. 2 viridis N ADP-me M.S. 3 erucaeformis PEP-ck 2 Urochloa plantaginea PEP-ck P.S. 2 bolbodes PEP-ck P.S. ■> platyphylla PEP-ck P.S. 2 mosambicensis PEP-ck P.S. -> ramosa PEP-ck P.S. 2 panicoides PEP-ck P.S. 3 xantholeuca PEP-ck 2 pa II idans PEP-ck P.S. 2 Cenchrus Panic em pauciflorus N ADP-me MS. 3 agrostoides NADP-me M.S. -> Digitaria antidotale NADP-me M.S. 1 decumbens N ADP-me MS. 6 bergii NAD-me P.S. 3 sanguinalis N ADP-me MS. 5 cap ilia re NAD-me P.S. 3 Echinochloa coloratem NAD-me P.S. 3 crus-galli N ADP-me MS. 3 decompositem NAD-me P.S. 3 colontun N ADP-me M.S. 3 fascicelatem PEP-ck P.S. 2 Eriochloa hallii NAD-me P.S. 3 borumensis PEP-ck P.S. 2 makarikariense NAD-me P.S. 3 ere bra PEP-ck 2 maximem PEP-ck P.S. 6 6 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 1 continued. Phot. Anat. Author1 Phot. Anat. Author gracilis PEP-ck PS. 2 miliaceum NAD-me P.S. 5 pseudoacro tri cha PEP-ck 2 / nolle PEP-ck P.S. 3 punctata PEP-ck PS. 2 obtusum NADP-me M.S. 2 sericea PEP-ck PS. 2 stapfianum NAD-me P.S. 3 Paspalum texanum PEP-ck P.S. 3 notatum N ADP-me MS. 3 turgidum NAD-me P.S. 3 Pennisetum Ps e ado bra ch ia ria purpureum NADP-me M.S. 1 deflexa PEP-ck P.S. 2 typhoides N ADP-me M.S. 6 AN D ROPO GON EAE Andropogon Sorghastrum gerardi NADP-me M.S. 3 nutans NADP-me M.S. 3 virginicus NADP-me M.S. 6 Sorghum Euchlaena bicolor NADP-me M.S. 3 mexicana NADP-me M.S. 3 sudanense NADP-me M.S. 3 Microstegium vulgare NADP-me M.S. 4 vimineum NADP-me M.S. 2 Zea Saccharum mays NADP-me M.S. 4 officinarum NADP-me M.S. 3 Schizachyrium scoparium NADP-me M.S. 3 C H LO R I DEAE Bouteloua Eleusine gracilis N AD-me PS. 3 indica NAD-me P.S. 3 curtipendula PEP-ck P.S. 3 Enteropogon Buchloe 2 species T dactyloides N AD-me PS. 2 Eustachys Chloris 6 species 2 distichophylla N AD-me P.S. 3 Leptochloa gayana PEP-ck P.S. 5 dubia NAD-me P.S. 3 17 species 2 monostachva NAD-me P.S. 3 ERAGROSTEAE Eragrostis curvula NAD-me P.S. 3, 5 cilianensis N AD-me P.S. 3 superba NAD-me P.S. T SPOROBOLEAE Muhlenbergia cryptandrus NAD-me P.S. 3 schreberi PEP-ck P.S. 3 fimbriata PEP-ck s Spo robot us poiretii PEP-ck P.S. 3 airoides NAD-me P.S. 3 MEMOIRS OF THE TORREY BOTANICAL CLUB 7 Table 1 continued. Phot. Anat. Author1 Phot. Anat. Author Zoysia japonica PEP-ck Z O Y S 1 E A E Hilaria P.S. 3 helangeri PEP-ck P.S. 2 A ristida parparea NADP-me ARIST1DEAE D.S. 3 Totals: 80 species; NADP-me, 29; NAD-me, 21; PEP-ck, 302. 'Authors: I) Brown and Gracen, 1972 2) Gutierrez. Edwards, and Brown, 1976; and Gutierrez and Edwards, unpublished 3) Gutierrez, et al., 1974 4) Hatch and Kagawa. 1974a 5) Hatch and Kagawa, 1974b 6) Kanai and Black, 1972 2Number of PEP-ck species is disproportionately large because of deliberate search for them in Brachiaria, Eriochloa, and Urochloa. Panicum fasciculatum, P. r nolle , and P. texanum have previously been transferred to Brachiaria . TABLE 2. C4 photosynthetic subtypes reported by others for u sedge and some dicotyledonous species, arranged by families. Cyperus rotundas Moll a go cerviana M . nudicaalis G isek ia pha rn a co ides T rianthema portulacastrum A Iternanthera pan gens A ma ran thus edtdis A . hyhridas A . palmeri CYPERACEAE NADP-me AIZOACEAE aspartate aspartate aspartate malate AMARANTHACEAE aspartate NAD-me N AD-me NAD-me (Chen, et al., 1974) (Kennedy and Laetsch, 1974) ( Rathnam, et al., 1976') ( Rathnam, et al., 1976) ( Rathnam, et al.. 1976) ( Rathnam, et al., 1976) ( Hatch, et al., 1975) (Gutierrez, et al., 1974) (Hatch, et al., 1975) 8 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS A . retroflexus A . tricolor A. viridis Froelichia gracilis Gomphrena celoso ide s G. globosa G. globosa T idestromia oblongifolia BOR H eliotropium sea brum N AD-me (Gutierrez, et al., 1974) N AD-me (Gutierrez, et al., 1974) aspartate (Rathnam, et al., 1976) NADP-me (Gutierrez, et al., 1974) NADP-me (Hatch, et al., 1975) NADP-me (Gutierrez, et al., 1974) malate? (Rathnam, et al., 1976) NADP-me (Bjorkman, et al., 1975) KG IN ACEAE malate (Rathnam, et al., 1976) Polycarpaea corymbosa CARYOPHYLLACEAE aspartate (Rathnam, et al., 1976) A triplex rosea CHENOPODI ACEAE aspartate (Pearcy and Bjorkman, A . sabulosa N AD-me (Bjorkman, et al., 1975) A . spongiosa N AD-me (Hatch, et al., 1975) Bassia hyssopifolia NADP-me (Downton, 1970) Kochia childsii NADP-me (Gutierrez, et al., 1974) K. scoparia NADP-me (Gutierrez, et al., 1974) Salsola kali NADP-me (Gutierrez, et al., 1974) Chamaesyce hirta EUPHORBI ACEAE malate (Rathnam, et al., 1976) C. maculata NADP-me (Gutierrez, et al., 1974) C. supina NADP-me (Gutierrez, et al., 1974) NYCTAGIN ACEAE Boerhaavia diffusa aspartate (Rathnam, et al., 1976) PORTULACACEAE Portulaca oleracea N AD-me (Hatch, et al., 1975) Portulaca oleracea N AD-me (Gutierrez, et al., 1974) Portulaca oleracea malate (Rathnam, et al., 1976) P. grandiflora NADP-me (Gutierrez, et al., 1974) Tribal us terrestris ZYGOPH YLLACEAE aspartate (Rathnam, et al., 1976) 'Rathnam, C. K. M., A.S. Raghavendra, and V. S. Rama Das. 1976. Z. Pflanzenphysiol. 77:283-291. 2Pearcy, F. W. and O Bjorkman. 1971. Carnegie Inst. Wash. Year Book 69:632-639. MEMOIRS OF THE TORREY BOTANICAL CLUB 9 The chloroplasts of the Kranz cells are more or less restricted in some species to the inner or centripetal regions, and in other species to the outer or centrifugal regions of the cells ( Brown, I960; Gutier¬ rez, Gracen, and Edwards, 1974). After long exposure to light these chloroplasts contain starch grains, whereas those of mesophyll cells usually do not. There¬ fore, iodine staining of thin cross sections of living leaves produces blue mesophyll if from a C3 plant, but a blue ring of Kranz tissue if from a C4 plant. Under the elec¬ tron microscope, chloroplasts that lie in the centrifugal regions of Kranz cells are observed to be of the NADP-me type in some species and of the PEP-ck type in others. The former contain few or no grana (Johnson, 1964; Laetsch, 1974; Bragnon, 1973; Kirchanski, 1975), whereas the latter contain large grana. Chloroplasts in the centripetal regions of Kranz cells are of the NAD-me type and have many large grana (Laetsch, 1974). They also have many associated mitochondria (Laetsch, 1974, for re¬ view), even in such intermediates as Punicum milioides (R. H. Brown, unpub¬ lished; Ku, et al., in press) and Mollugo verticillatci (Kennedy and Laetsch, 1974). It is often stated that the walls of Kranz cells are thicker than those of mesophyll cells (Downton, 1971b; Laetsch, 1974), and that is true. But it is also true that there is great variation in Kranz cell wall thickness itself. Among the Kranz grass¬ es some such walls are five or six times as thick as others. Lurthermore, considera¬ ble range in thickness occurs within tribes and genera as well as within the anatomi¬ cal and enzymatic subtypes. Among the Kranz dicotyledons the walls of Kranz cells are almost without exception very thin, often only about twice as thick as those of the mesophyll cells, and no sub- erized layer has been observed in them (Laetsch, 1974; personal observation). The models of C4 photosynthesis (Hatch, et al., 1975) propose that the Kranz cell wall is a barrier separating the PEP-carboxylase reaction in the mesophyll cells from the decarboxylating and RuDP-carboxylase reactions that occur within the Kranz cells. It has also been proposed that in grasses an impervi¬ ous suberized layer on the outer tangen¬ tial and radial wall surfaces of the Kranz cells provides or adds to the barrier effect of the thick walls ( Laetsch, 1974). Trans¬ port pathways between mesophyll and Kranz protoplasts are provided by numerous plasmodesmata that penetrate the thick Kranz cell walls (Johnson, 1964; Laetsch, 1974). In C4 species, C02 incorporation by PEP-carboxylase does not discriminate against the 13C atoms of C02 as does that by ribulose diphosphate carboxylase in C3 species (Whelan, Sackett, and Benedict, 1973). As a result, the or¬ ganic matter of Kranz plants has a 13C/12C ratio not much different from that of C02 in the air. The organic matter of non- Kranz species is, on the other hand, much lower in 13C. As expressed in the litera¬ ture, relative to the PDB carbonate stan¬ dard, C4 species have high negative ratios (between -9 and -18 °/00), whereas C3 plants have low ratios (between -22 and -38 °/00) (Bender, 1968; Smith and Brown, 1973; Troughton, et al . , 1 974) . Such ratios are probably the best evi¬ dence obtainable for indicating whether an angiospermous plant is Kranz or 10 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS non-Kranz, provided it is neither aquatic nor succulent. Also, because of the different re¬ sponses of ribulose diphosphate carbox¬ ylase and PEP-carboxylase to oxygen, non-Kranz plants have increasingly greater photosynthetic activity as the ox¬ ygen concentration in the ambient at¬ mosphere is lowered from the 21 percent of air to about 2 percent. Kranz plants, however, function with constant effi¬ ciency throughout this range (Brown and Gracen, 1972; Brown and Brown, 1975). C3 plants carry on a process called photorespiration; C4 plants may also, but if so it is undetectable. As a result, non- Kranz plants in a closed system can only reduce the C02 concentration from the 320 ppm of air to about 50 ppm. Kranz plants, on the other hand, are able to re¬ duce the C02 concentration to about zero. These limits are called C02 com¬ pensation points (Krenzer and Moss, 1969), determination of which permits rather rapid survey of species in large numbers to determine whether C3 or C4 (Krenzer, Moss, and Crookston, 1975). Uniquely, Panicum milioides and P. hians are definitely intermediate (15-20 ppm) in CO-2 compensation point and ox¬ ygen effect (Brown and Brown, 1975; R. H. Brown, unpublished). The photorespiration of non-Kranz plants produces a burst of C02 just after removal from light to dark. This is called the C02 postillumination burst or PIB. There are also, however, some Kranz plants, the aspartate formers, that show a PIB of sorts (Brown and Gracen, 1972). Since 1965, all these differences be¬ tween non-Kranz and Kranz states have been used as criteria for assigning plants to one or the other category. Until then, leaf anatomy was the only character known, or adequately enough known, for such use. The Kranz syndrome has been found: only in terrestrial angiosperms; in no trees or bushes except some woody species of Atriplex, Heliotropium, and Euphorbia (Chamaesyce) in Hawaii (Percy and Troughton, 1974); only be¬ tween latitudes 45° N and 45° S; usually in plants of bright sunny habitats; and, in temperate zones, in plants growing only during the hot season. So far it has been reported: in twelve families of angio¬ sperms; in a large number of genera in the Gramineae, Cyperaceae, and Chenopodiaceae; and in smaller num¬ bers of genera (often only in one or part of one genus) in the Amaranthaceae, Compositae, Euphorbiaceae, Nyctagi- naceae, Portulacaceae, Molluginaceae, Zygophyllaceae, Boraginaceae, and Caryophyllaceae. No family is all Kranz and many genera contain both Kranz and non-Kranz species. Kranz species range in habitat from very wet (some species of Cyperus, some grasses, some Hawaiian species of Chamaesyce, etc.) to very arid ( Atriplex , Kallstroemia, Tidestromia, and some grasses), but are almost always found in bright sunlight and usually in hot regions (Kawanabe, 1968; Bjorkman, et al., 1972; Troughton, et al., 1974). It has long been recognized that certain taxa (genera, tribes, and subfamilies) are entirely either Kranz or non-Kranz. Realization that some taxa are anatomi¬ cally heterogeneous developed slowly: Holm (1901) and de Winter (1965) for Aristideae; Potztal (1952) and Tateoka (1957) for Panicoideae and Paniceae; de MEMOIRS OF THE TORREY BOTANICAL CLUB Wet (1954) for Danthonieae; Brown (1958) for Panicum. During the 1960's numerous studies confirmed that the Paniceae and Panicum contain both Kranz and non-Kranz taxa. This was made very evident in a survey of the fam¬ ily by ,3C/12C ratios (Smith and Brown, 1973). The primary intent of this investigation was to survey as many genera and species of the Paniceae as possible, and many sections and species of Panicum . Though each of these taxa was known to contain both Kranz and non-Kranz species, only a minority had actually been charac¬ terized by any of the techniques known to differentiate the two states. The anatomi¬ cal and physiological data acquired were to be analyzed for taxonomic significance at the generic and sectional levels. In addition, selected species from other tribes of the Panicoideae as well as from other subfamilies, especially the Danthonieae, Aristideae, and Eragros- toideae, were to be studied similarly. As originally planned, the investigation was to be of 13C/12C ratios; study of leaf anatomy came later. The latter soon be¬ came the more significant as it revealed relationships between Kranz anatomical subtypes and C4 biochemical subtypes. The overall investigation promoted studies, some quite extensive, of the Cyperaceae and certain dicotyledonous families (Webster, Brown, and Smith, 1975, of the Euphorbiaceae; Smith and Turner, 1975, of the Compositae; and others now underway). MATERIALS AND METHODS Nearly all the materials examined were 1 1 from herbarium specimens. Such mater¬ ial is as good as living for determining 13C/12C ratios, and for most of the anatomical study it was quite adequate, excepting a few species. Specimens were borrowed from herbaria with permission to remove samples. The herbaria provid¬ ing them are listed, with their abbrevia¬ tions, under “Terminology and nota¬ tion.” Each specimen tested was tick¬ eted, stating the 13C/12C ratio and/or the type of leaf anatomy (N for non-Kranz; K, M.S. for the M.S. subtype of Kranz anatomy; or K, P.S. for the P.S. subtype of Kranz anatomy). Pieces of leaves for anatomical study were boiled a few minutes and then freehand cross sections were cut with a sharp razor blade in water under a dissecting microscope. The sections were examined in water under a cover glass with a compound microscope. A second procedure was also followed for Kranz species and for those difficult to characterize as Kranz or non-Kranz from cross sections. A boiled piece was positioned in water, flat on the stage of the dissecting microscope, adaxial (upper) side up. It was then repeatedly scraped parallel to the stage with a razor blade until some lower epidermis became visible. In water under a cover glass, the paradermal appearance of the bundle sheath and Kranz cells was then observed with a compound microscope (Brown, 1974, 1975). ,3C/12C ratios (or 813C °/00 numbers) were determined as follows. Dried tissue (5-10 mg) was burned at 800° C in an excess of oxygen, and isotope ratios of the C02 evolved were measured on a Nier-type mass spectrometer modified 12 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEM AT1CS according to McKinney , et al. ( 1950). Re¬ sults are reported relative to a carbonate standard in terms of 8|:!C, calculated according to the formula 8i:iC °/nn = 1000 [( R sample/R standard) - I] where R = mass 45/mass 44 of sample or standard C02. The standard used was carbonate from the fossil skeleton of Belemnitella a meric ana from the Peedee formation of South Carolina (the PDB standard). Sample replication was ± 0.2 °/00 , but different samples of a species taken from different locations can vary by a few pails per thousand. For this work it is meaningful only whether a ratio falls in the high, C4 range ( -9 to - 18 °/00) or in the low, C3 range (-22 to -36 °/00). As far as known there is always a gap of at least 4 °I0I) between high and low ranges in grass¬ es, which makes this a very reliable method of characterizing a sample as C3 or C4 (Smith and Epstein, 1971). TERMINOLOGY AND NOTATION N or Non-kranz — Having no specialized Kranz tis¬ sue in the leaves, an anatomical condition corre¬ lated with C3 photosynthesis. For description see text. k or kranz — Having specialized kranz tissue in the leaves, an anatomical condition correlated with C4 photosynthesis. For description see text. Subscripts of N or k: a — Determined by anatomical examination, r — Inferred from determination of photosynthetic type by l3C/12C ratio. c — Inferred from determination of photosynthe¬ tic type by C02 compensation point, e — Determined by electron microscopic exami¬ nation. M.S. — That subtype of kranz anatomy in which the kranz sheath has evolved from a mestome sheath. For description see text. P S. — That subtype of kranz anatomy in which the kranz sheath has evolved from a parenchyma sheath. For description see text. D.S. — That subtype of kranz anatomy in which a double kranz sheath is present; limited to Aristida. For description see text. 813C — 13C/12C ratio; -9 to -18 °l00 = C4 photosynthesis (kranz); -22 to -35 °/00 = C3 photosynthesis (non-kranz). C3 — Having the Calvin (Calvin-Benson) type of photosynthetic dark reaction. For description see text. C4 — Having the Hatch-Slack type of photosynthe¬ tic dark reaction. For description see text. NADP-me — That subtype of C4 photosynthesis in which NADP-malic enzyme is the dominant de¬ carboxylase in the kranz tissue. NAD-me — That subtype of C4 photosynthesis in which NAD-malic enzyme is the dominant de¬ carboxylase in the kranz tissue. PEP-ck — That subtype of C4 photosynthesis in which PEP-carboxykinase is the dominant de¬ carboxylase in the kranz tissue. Herbaria: k — Royal Botanic Gardens, kew, England. NSW — National Herbarium, Sydney, Australia. P — Faboratoire de Phanerogamie, Museum Na¬ tional d'Histoire Naturelle, Paris, France. PRE — National Herbarium. Pretoria, Republic of South Africa. TEX — University of Texas, Austin. US — U. S. National Herbarium. Smithsonian Institution, Washington, D. C. THE PANICEAE The significant early contribution of leaf anatomy to grass systematics was the belief that major taxa(subfamilies, tribes, subtribes, and genera) uniformly had either Kranz or non-Kranz anatomy. For example, all taxa of the subfamily Panicoideae were reported to have Kranz anatomy, hence the term “pan'c°id" for that type of leaf anatomy (Hubbard, 1948). Many Kranz genera and subtribes of the putatively non-Kranz Fes- tucoideae were transferred to the Panicoideae on this basis, but that pro¬ duced the need for a second Kranz sub¬ family, the Eragrostoideae. During the 1950’s it became evident (in MEMOIRS OF THE TORREY BOTANICAE CLUB 13 retrospect) that some Panicoideae did not have panicoid leaf anatomy. Potztal (1952) reported “festucoid” leaf anatomy in the small tribe Isachneae of the Panicoideae. Tateoka ( 1956a) and Brown ( 1958) observed the same in a few genera of the Paniceae, including Panicum. Smith and Brown (1973), Ellis (1974a), and others during recent years have re¬ ported festucoid anatomy in additional species of Panicum and other genera of Paniceae. This inconsistency in terms has led to the use of “non-Kranz” for “festucoid” and “Kranz” for “pani¬ coid' ' leaf anatomy (Brown, 1975). Throughout the remainder of the text it is assumed that all species having M.S. anatomy are NADP-me, those with P.S. anatomy and centripetal chloroplasts are NAD-me, and those with P.S. anatomy and centrifugal chloroplasts are PEP-ck. These are presently acceptable generali¬ zations which will be treated as facts. The methods used and materials avail¬ able permitted examination of at least one (and usually more) species in each of es¬ sentially all genera of the Paniceae. Often, more than one specimen of a species was examined to confirm obser¬ vations. Little attempt was made to check the validity of the names found on speci¬ men sheets. Therefore, some names re¬ ported may be incorrect. As Hsu (1965) discovered, it is impos¬ sible to discuss the rest of the Paniceae separately from the genus Panicum. This is true partly because Panicum constitutes a large part of the tribe. Furthermore, the transfer of many species and sections out of Panicum by some agrostologists but not by others re¬ quires balanced consideration. And the two taxa are further entangled because all the discussed variations found in the tribe are also found within the genus. Such ex¬ treme diversity in putatively fundamental taxonomic characters, leaf anatomy and photosynthesis types, within one genus indicates a peculiar relationship to the higher inclusive taxon. The two have been treated here in separate sections for simplicity and clarity. However, throughout the discussion of each, refer¬ ences to the other are numerous. Table 3 reports data for 297 species of 86 genera examined. Excluded are species of Panicum and Dichanthelium, which are treated separately. Numbers in parentheses following specific names in¬ dicate the numbers of specimens ex¬ amined for 8 13C and/or‘anatomy. Table 4 summarizes data for 90 genera of Paniceae, including Panicum and Dichanthelium. This survey of the Paniceae is very complete for genera. Bews (1929) listed about 60 genera now considered to belong in Paniceae. Pilger ( 1954) listed 79 genera as constituting the tribe. The 86 genera covered here do not include five listed by Pilger, but do include a number of pres¬ ently recognized or tentative genera not listed by him (such as Psilochloa, Paraneurachne , Thyridolepis, Pseudo- hrachiaria, and Dichanthelium). About eight genera of Paniceae are lacking along with other genera included by some but excluded by Pilger and the author (such as Anthephora and Trachys). The small panicoid tribes recognized by Pilger (An- thephoreae, Arthropogoneae, Arundinel- leae, Cyphochlaeneae, Lecomtelleae, Melinideae, and Trachyeae) are also ex¬ cluded from Paniceae here and treated separately. 14 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEM AT1CS TABLE 3. Spec ies of Paniceae (less Panicum) examined , ar¬ ranged by genera: anatomical and photosynthetic characters , provenances, and voucher herbaria: with new combinations under Steinchisma. 813C Anat. Prov. Herb. Acroceras amplectans -21.1 Nr Africa US basicladum -27.3 Nr Africa US macrum -26.1 Nr Africa US munroanum -28.8 Nr Asia US paucispicatum (see text) pilgerana (see Psilochloa) tonkinensis (see Neohusnotia) -11.6 PS. S. Am. TEX zizanioides (4) -29.8 Nar S. Am. TEX A critochaete volkensii -30.7 Nr Africa US Alloteropsis angusta (2) cimicina (see Coridochloa) -12.2 M.S. Africa PRE gwebiensis (2) paniculata (see Coridochloa ) quintasii (see Coridochloa) -11.9 M.S. Africa PRE semialata (17) ca. -11 M.S. various many var. eckloniana (8) ca. -26 Nar Africa PRE A mphicarpum purshii -26.7 Nar U.S.A. TEX muhlenbergianurn -28.1 Nar U.S.A. TEX A n ci s tra ch n e an ci n ala ta -24.4 Nr Aust. US Anthaenantia rufa -12.2 M.S. U.S.A. TEX villosa -15.3 M.S. U.S.A. TEX Anthaenantiopsis rajas iana - 12.3 M.S. S. Am. US perforata -12.0 M.S. S. Am. US Axonopas affinis -10.6 M.S. U.S.A. TEX appendiculatus M.S. S. Am. TEX deludens M.S. S. Am. TEX sco pari us -10.8 M.S. S. Am. TEX Beckeropsis procera -18.1 M.S. Africa US uniset a M.S. Africa TEX Bracheria brizantha P.S. Africa TEX ciliatissima P.S. U.S.A. TEX decurnbens P.S. Africa TEX echinulatum P.S. S. Am. TEX eruciformis P.S. Aust. TEX foliosa P.S. Aust. TEX leucantha P.S. Africa TEX rn utica P.S. Africa TEX marlothii P.S. Africa TEX negropedata P.S. Africa TEX ophryodes P.S. Mexico TEX plantaginea P.S. Mexico TEX platyphylla -12.7 P.S. U.S.A. TEX MEMOIRS OF THE TORREV BOTANICAL CLUB 15 Table 3 continued. 813C Anat. Prov. Herb. poaeoides -13.2 P.S. Africa US ramosa P.S. India TEX reptans -1 1.4 P.S. World TEX ruzizensis P.S. Africa TEX scalaris P.S. Africa TEX serrata P.S. Africa TEX xantholeuca P.S. Africa TEX C alyptoch loa gra cilli ma -25.1 Nr Aust. US Cenchrus ciliaris (2) -11.3 MS. U.S.A. TEX incertus -11.5 MS. U.S.A. TEX my o suro ides -11.9 M.S. U.S.A. TEX palmeri MS. Mexico TEX tribuloides MS. U.S.A. TEX Centrochloa singularis -13.1 MS. S. Am. US Chcietium bromoides (3) — 12.2 P.S. Mexico TEX cubanun (3) -12.4 MS. Cuba US. TEX festucoides (2) -12.5 M.S. S. Am. US, TEX Chamaeraphis hordeacea — 12.2 MS. Aust. US Cleistochloa subjuncea -23.8 Nr Aust. TEX sclerachne -26.6 Nr Aust. US Chloachne oplismenoides -29.6 Nr Africa PRE Commelinidium gabunensis -32.6 Nr Africa US meyumbense -27.9 Nr Africa US nervosum -31.0 Nr Africa US Coridochloa cimicina (5) ca. - 13 P.S. various PRE quintasii (2) -12.9 P.S. Africa PRE paniculata -13.0 P.S. Africa PRE Cymbosetaria sagittifolia -12.1 M.S. Africa PRE Cyrtococcum accrescens -29.1 Nr Africa US chaetophoron -31.7 Nr Africa US oxyphyllum -28.8 Nr Aust. US patens -28.6 Nr Africa US trigonum -31.6 Nr Asia US Dichanthelium (73 species, all) Nar Amer. TEX. US Digitaria adscendens -11.6 Kr U.S.A. TEX decumbens M.S. Africa TEX longifolia -13.7 M.S. Africa US perrottetii M.S. Africa US sanguinalis -12.7 M.S. U.S.A. TEX smutsii M.S. Africa TEX zeyheri -11.2 M.S. Africa US Dimorphochloa rigida -25.6 Nar Aust. NSW Dissochondrus biflorus -13.1 M.S. Hawaii TEX Echinochloa colonum M.S. U.S.A. TEX crusgalli -1 1.4 M.S. U.S.A. TEX THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 3 continued. 813C Anat. Prov. Herb. cruspavonis M.S. U.S.A. TEX haploclada -11.6 M.S. Africa US holciformis MS. Africa TEX hulubii M.S. Africa US oplismenoides -15.3 S. Am. TEX paludigena M.S. USA. TEX polystachya M.S. U.S.A. TEX pyramidalis M.S. Africa TEX walteri M.S. U.S.A. TEX zelayensis -12.3 M.S. Aust. US Echinolaena gracilis -29.5 Nr S. Am. US inflex a -26.2 Nr S. Am. US madagascariensis -29.6 Nr Madag. US Entolasia imbricata -27.3 Nr Africa PRE marginata -27.3 Nr Aust. NSW stricta -24.2 Nr Aust. NSW Eriochloa aristata -12.8 PS. U.S.A. TEX borumensis PS. Africa TEX contractu PS. U.S.A. TEX distachya P.S. S. Am. TEX gracilis PS. U.S.A. TEX lemmonii P.S. Mexico TEX michauxii -11.9 P.S. U.S.A. TEX nelsonii P.S. Mexico TEX nubica (2) P.S. Africa TEX platystachya P.S. S. Am. TEX punctata -11.8 P.S. U.S.A. TEX ramosa P.S. S. Am. TEX sericea -16.3 P.S. U.S.A. TEX villosa (2) P.S. Asia TEX H ole o lemma ca n icu la t am - 1 1.7 M.S. Asia US Homolepis aturensis (2) -27.6 Nr S. Am. TEX isocalycia -28.4 Nr S. Am. US Homopholis belsonii -23.9 Nr Aust. US Hymenachne acutigluma -27.1 Nr Asia US amplexicaulis (3) ca. -28 Nr S. Am. US as sa mica Na Asia US donacifolia -28.3 Nr S. Am. TEX hemitonom (see text) _2s.2 Nr U.S.A. TEX pse udo-interrupta -25.8 Nr Asia US Ichnanthus australiensis (2) -13.0 Kar Aust. NSW. US ba mb us i floras -27.7 Nr S. Am. US brevivaginatus -32.4 Nr S. Am. US cand icons -29.1 Nr S. Am. TEX camporum -29.0 Nr S. Am. US MEMOIRS OF THE TORREY BOTANICAL CLUB 17 Table 3 continued. 813C Anat. Prov. Herb. confertus -29.9 Nr S. Am. US foliolosus -12.0 Kr Asia KEW lotifolios -29.6 Nr S. Am. US nemorosus -26.3 Nr S. Am. US pollens (3) ca. -31 Nr S. Am. TEX pauciflorus -11.8 Kr Aust. US proem t ens Na S. Am. US trinii -25.3 Nr S. Am. US venezuelanus -28.8 Nr S. Am. US vie inns -29.3 Nr S. Am. US Ixophorus onisetos (3) -12.3 MS. Mexico US. TEX Lo sine is di \ a ri ca to -25.6 Nar S. Am. TEX grisebachii -27.5 Nar S. Am. US linearis Na S. Am. US proeerrima -25.8 Nr S. Am. TEX rtigelii Na S. Am. US rusci folia -24.4 Nr S. Am. TEX sloonei Na S. Am. US Lep toeo ryphe ton hi no tom -1 1.0 M.S. S. Am. TEX Leptolo mo o re n ieo lo MS. U.S.A. TEX eo gnat ton — 1 2.2 MS. US. A. TEX Leptasacehorum filiforme -1 1.0 MS. S. Am. US Leucophrys glome rota (2) PS. Africa US. TEX mesocomo (Ellis) PS. Africa PRE Megoloprotochne albescens -12.0 MS. Africa PRE M esosetum filifolium -12.3 M.S. S. Am. US loliiforme - 12.3 M.S. S. Am. US pit t ie rt -12.5 M.S. S. Am. TEX Microcalamus ospidistrulo -33.6 Nr Africa PRE N eohusnotio tonkinensis -29.4 Nr Asia US Neuraehne munroi (3) — 13.3 M.S. A list . NSW Odon telytrum a byss in ieo m -13.5 M.S. Africa PRE Oplismenopsis nojado -26.9 Nr S. Am. US O pi is me nos bnrmannii -27.5 Nr S. Am. TEX hirt edits (2) -31.0 Nar Mexico TEX rari floras Na S. Am. TEX setorios -26.2 Nr U.S.A. TEX O ryzidi am bo rn a rdii - 12.8 P.S. Africa PRE. US Otachyriam inoeqoole -26.8 Nar S. Am. US pterigodiom -27.2 Nar S. Am. US versicolor -25.3 Nar S. Am. US Ottoehloo ornottiono -26.6 Nar Africa US Jits CO -26.0 Nr Asia US grocillimo -30.4 Nr Aust . US nodosa -27.1 Nar Asia US THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 3 continued. §>3C Anat. Prov. Herb. Panicum (241 spp. of all sorts.) Paractaenum novae-hollandiae -12.3 M.S. Aust. US Paraneurachne muelleri (3) ca. - 12 M.S. Aust. TEX, US (Jacobs) Ka Aust. NSW Paratheria prostrata -11.0 M.S. Africa PRE Paspalidium constrict am -14.6 M.S. Aust. NSW flavidum M.S. Aust. NSW geminatum (2) -11.3 M.S. Aust. NSW. TEX jubiflorum (2) -11.9 M.S. Aust. US paludivagum -12.8 M.S. U.S.A. TEX pan datum -11.9 M.S. Asia US Paspalum decumbens M.S. S. Am. US distichum M.S. U.S.A. TEX fimbriatum -12.5 M.S. S. Am. US floridanum M.S. U.S.A. TEX inaequivalve M.S. S. Am. US langei M.S. U.S.A. TEX lineispatha M.S. S. Am. US longicuspe M.S. Mexico TEX macrophyllum M.S. S. Am. US monostachyum M.S. U.S.A. TEX notation ( Bender, 1968) (-13.2) M.S. U.S.A. publiflorum -12.6 M.S. U.S.A. TEX repens M.S. S. Am. US saccharoides -11.6 M.S. S. Am. US sericatum M.S. S. Am. US sodiroanum M.S. S. Am. US stellatum -11.8 M.S. S. Am. US urvillei -13.3 U.S.A. TEX vaginatum M.S. S. Am. US Pennisetum purpureum (2) M.S. C. Am. TEX setosam (2) -14.7 M.S. S. Am. TEX villosum M.S. U.S.A. TEX Phanopyrum gymnocarpon (2) -29.1 Nar U.S.A. TEX Plagiosetum refraction -12.3 M.S. Aust. US Poecilostachys festucaceus -31.5 Nr Africa PRE Pseudechinolaena polystachya -30.4 Nr World TEX madagascariensis -29.9 Nr Madag. P Pseadobrachiaria deflexa (3) - 12.2 P.S. Africa PRE, TEX Pseudochaetochloa aastraliensis -11.4 M.S. Aust. US Pseudoraphis paradoxa -12.0 M.S. Asia US spinescens -10.8 M.S. Asia US Psilochloa pilgerana -11.9 P.S. Africa PRE Reimarochloa acuta (2) - 12.2 M.S. S. Am. TEX MEMOIRS OF THE TORREY BOTANICAL CLUB 19 Table 3 continued. 5|:'C Anat. Prov. Herb. Sacciolepis africana -26.5 Nr Africa TEX campestris -24.5 Nr S. Am. TEX curvata (2) -26.3 Nr Africa PRE, TEX delicatula -25.9 Nr Madag. US glaucescens -24.7 Nr Africa US indica -26. 1 Nr India US micrococca -26.4 Nr Africa US my urns -24.9 Nr S. Am. TEX interrupt a -24.3 Nr Africa US striata -27. 1 Nr US. A. TEX strumosa -24.9 Nr S. Am. TEX transbarhata -25.9 Nr Africa US Scutachne amphistemon - 9.2 PS. W. lnd. US dura — 15.7 PS. W. lnd. US Set aria bar bat a -10.8 MS. S. Am. US chevalieri MS. Africa TEX globulifera -12.5 M.S. S. Am. US italica -13.8 NTS. cult. TEX leiantha M.S. S. Am. US leucopila M.S. USA. TEX magna M.S. U.S.A. TEX membranifolia -12.0 M.S. S. Am. US palmifolia M.S. S. Am. TEX paniculifera (3) M.S. S. Am. TEX poiretiana -1 1.2 M.S. S. Am. US scandens -12.1 M.S. S. Am. US scheelei -12.6 M.S. U.S.A. TEX viridis (Bender, 1968) Paurochaetium (subgenus) (-13.3) M.S. U.S.A. TEX chaprnanii (2) M.S. C uha TEX distantiflorurn M.S. C u ha TEX ftnnulum M.S. U.S.A. TEX lean is M.S. Cuba TEX ophiticola M.S. Cuba TEX ramiselum -1 1.7 NFS. U.S.A. TEX reverehonii -1 1.9 M.S. U.S.A. TEX utawaneum M.S. W. lnd. TEX Setariopsis auriculata M.S. Mexico TEX latiglumis -12.2 M.S. Mexico TEX Spheneria kegelii (2) — 11.9 M.S. S. Am. US. TEX Spinifex littoreus Steinchisma (see text) -12.2 PS. Asia US cuprea' (2) -26.9 Nr S. Am. US. TEX decipiens 2 -26.7 Nr S. Am. US exigui flora 3 (2) -28.1 Nr S. Am. US. TEX 20 IHH KR AN/ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 3 continued hians (3) milioides (10) Stenotaphrum secundatum Stereochlaena came ro n ii Streptolophus sagittifolius Streptostachys asperifolium T arigidia aequiglumis T hrasya campylostachya petrosa trinitensis T hrasyopsis cinerascens repandam Thuarea involuta (2) Thyridolepsis alopecaroides (2) mitchelliana (2) multiculmis (Jacobs) x erophila (Jacobs) T ri cha ch ne ca lifo rn ica hitchcockii insularis sacchariflora Triscenia ovina (2) Uranthoecium truncatam (2) Urochloa bolbodes helopus mosambicensis panicoides pullulans Xerochloa barbata cheribon laniflora Zygochloa paradox a Anat. Prov. Herb. Nr U.S. A. TEX Nar S. Am. TEX MS. world TEX M.S. Africa US M.S. Africa US Nr S. Am. US M.S. Africa PRE M.S. S. Am. US M.S. C. Am. US M.S. S. Am. TEX M.S. S. Am. US M.S. S. Am. US P.S. Asia US Nar Aust. US, NSW Nar Aust. NSW Na Aust. NSW Na Aust. NSW M.S. U.S. A. TEX M.S. Mexico TEX M.S. U.S. A. TEX M.S. Mexico TEX Nr Cuba US, TEX M.S. Aust. US P.S. Africa TEX P.S. Africa US P.S. Africa TEX P.S. Africa US P.S. Africa TEX M.S. Aust. US M.S. Aust. US M.S. Aust. NSW M.S. Aust. US 813 C -26.0 ca. -26 -15.7 -10.8 -11.6 -27.0 -1 1.3 -12.0 -12.2 -11.0 -11.1 -12.2 -26.1 -25.3 -31.6 -11.7 -10.8 -12.1 -1 1.5 -12.1 -11.0 -12.2 -14.2 1 Steinchisma cuprea, comb, not-.: Panicum cupreum Hitchcock & Chase. Contr. U.S. Natl. Herb. 15:120. 1910. 2Steinchisma decipiem, comb, nov.: Panicum decipiens Nees, Agrost. Bras., 193; in Martius, Flora Bras. 2. 1829. 3Steinchisma exiguiflora, comb, nov.: Panicum exiguiflorum Griseb., Cat. PI. Cuba. 234. 1866. The coverage of species is much less complete, especially for large genera such as Digit aria, Set aria, Sacciolepis, /ch nan thus, P as pal um , Axonopus , Brachiaria, and Pennisetum. Never¬ theless, these large genera were delib¬ erately surveyed for unusual sub¬ generic types and, in combination with other data on leaf anatomy accumulated during the past hundred years, I believe MEMOIRS OF THE TORREY BOTANICAL CLUB this was adequate to characterize them quite reliably. The species of Paniceae examined, including those of Dichanthelium (72) and Panicum (241) treated separately, total 610, or more than one third of the tribe. As summarized in Table 4, the 21 Paniceae include many genera (33) that are non-kranz, nearly 38 percent, and more (57) that are Kranz, about 62 per¬ cent. The kranz genera are of two sub- types: M.S., 44 genera, about 78 percent; and P.S., 13 genera, about 22 percent. TABLE 4. Genera of Paniceae examined , arranged according to types of leaf anatomy and photosynthesis.1 Approximate total numbers of species per genus (Hubbard, 1973) given in parentheses . NON-KRANZ KRANZ M.S., NADP-me P.S., NAD-me and PEP-ck Acroceras (15) Anthaenantia (2) Brachiaria (PEP-ck) (60) Acritochaete ( I ) Anthaenantiopsis ( 1 ) Eriochloa (PEP-ck) (20) Alloteropsis ( 1 ) . - Alloteropsis (4) . — Coridochloa (3) Amphicarpum (2) Axonopus (35) Leucophrys (2) Ancistrachne (2) Beckeropsis (6) Oryzidium ( 1 ) Calyptochloa ( I ) Cenchrus (25) Pseudobrachiaria (PEP-ck) (1) Chloachne (2) Centrochloa (1) Psilochloa ( 1 ) Cleistochloa (2) Chaetium (2) . — Chaetium ( 1 ) Commelinidium (3) Chamaeraphis ( 1 ) Scutachne (2) Cyrtococcum (12) Cymbosetaria jl(l) Thuarea (2) Homopholis ( 1 ) . — Digitaria (380) Urochloa (PEP-ck) (25) Panicum ( 100 + ) . ---- Panicum (20 + )— . - — Panicum (NAD-me) (117 + ) Dichanthelium (120) Dissochondrus ( 1 ) Spin if ex (3) Dimorphochloa ( 1 ) Echinochloa (30) Echinolaena (6) Holocolemma (2) En tolas ia (5) Ixophorus (3) Ho mole pis (3) Leptocorypheum ( 1 ) Hymenachne (8) Leptoloma (2) Ichnanthus (26) Leptosaccharum ( 1 ) Lasiacis (30) Megaloprotachne (1) Microcalamus (4) Mesosetum (35) Thyridolepis (4) . — Neurachne (5) Neohusnotia (4) Odontelytrum ( I ) Oplismenopsis ( 1 ) Paractaenum (1) Oplismenus (15) Paratheria (2) Otachyrium (4) Paspalidium (20) Ottochloa (6) Paspalum (250) Phanopyrum ( 1 ) Pennisetum ( 1 30) Poecilostachys (20) Plagiosetum ( 1 ) Pseudechinolaena (2) Pseudchaetochloa (1) THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMAT1CS Table 4 continued. NON-KRANZ KRANZ M.S., NADP-me P.S., NAD-me and PEP-ck Sacciolepis (30) Pseudoraphis (!) Steinchisma (4) Reimarochloa (5) Triscenia (1) Set aria (140) Setariopsis (2) Stenotaphrum (7) Stereochlaena (1) Streptolophus (1) Tarigidia (1) T h rosy a (15) Thrasyopsis (2) Trichachne (15) Uranthoecium (1) Xerochloa (4) Zygochloa (1) Genera 33 Genera 44 Genera 13 Total 86 Species 433 + Species 1 170 + Species 237 + Total 1.840 1 Alloteropsis. Chaetium, and Panicum are listed in more than one column. In general, any particular grass genus is either entirely kranz or entirely non- kranz. The only known exceptions are the very large genus Panicum and the small Old World genus Alloteropsis. For Panicum , it can be proposed that the genus is artificial and that the only true Panicum species are those which are kranz P.S., NAD-me. In Alloteropsis, on the other hand, the only non-kranz taxon is the South African variety eckloniana of the widespread A. semialata. If that variety is retained in its present status, this is the only angiosperm species presently known to contain both kranz and non-kranz elements. As previously constituted, only three kranz genera contain both M.S.and P.S. taxa: Alloteropsis (s. lat.); the small American genus Chaetium; and Panicum. In Alloteropsis, the P.S. taxa are here segregated as the revived genus Coridochloa . In Panicum, the P.S., PEP-ck taxa are removed to the Urochloa-Brachiaria-Eriochloa com¬ plex, and the very few M.S. taxa (Table 8) are candidates for new generic status. In Chaetium, the problem has not yet been resolved, but future taxonomic changes may result. Two other cases of kranz/ non- kranz distinction between similar genera exist: the Australian genus Homopholis is like a primitive, non-kranz Digitaria (Dr. S. Jacobs, pers. comm.); and non-kranz Thyridolepis is closely related to kranz Neurachne . Jacobs also reports that a third genus, Paraneurachne , belongs in this latter Australian complex and that it has kranz anatomy. Thus, within the group “Neurachneae” Blake there are two kranz and one non-kranz genera. MEMOIRS OF THE TORREY BOTANICAL CLUB 23 among which, according to Jacobs, N eurachne seems to be the least specialized. From the present sample of Paniceae, it seems evident that the tribe is heterogeneous; no other tribe or subfam¬ ily contains such large proportions of taxa representing each of the various types of photosynthetic biochemistry and leaf anatomy. Some comments about a few other genera seem appropriate here. Acroceras (type species, A . zizanioides Dandy) has included species with charac¬ ters that warrant their removal. Hsu (1965) supported the transfer of A. ton- kinensis, A . amplectans , and A . macer to N eohusnotia A. Camus. Acroceras pilgerana Schweick has recently been segregated as Psilochloa pilgerana (Schweick) Launert (1970). I find P. pilgerana to be Kranz whereas Acroceras and N eohusnotia are non-Kranz. There¬ fore, the erection of Psilochloa is sup¬ ported. A southern South American species, A. paucispicatum (Morong) Henrard has Kranz P.S. anatomy, C4 photosynthesis, racemose inflores¬ cences, and transversely rugose lemmas. Since Acroceras (s. str.) is non-Kranz and has essentially smooth lemmas, A. paucispicatum is placed in the Brachiaria group (see later) for the present. How¬ ever, it may deserve generic rank. Most species with laterally com¬ pressed glume and lemma tips, by which Acroceras was considered distinguish¬ able, were included in that genus. But now, with Psilochloa and N eohusnotia separated and A . paucispicatum removed from Acroceras , and in view of the fact that some species of Mesosetum also ex¬ hibit such compression (Chase, 191 1), it becomes obvious that this characteristic is not of generic value. The laterally com¬ pressed tips may be the early stage of the evolution of awns. Among these taxa, the compression is most extreme in A. paucispicatum, here allied with Brachiaria and Eriochloa, some species of which do have awned glumes and/or lemmas. Chase (1911) considered Alloteropsis cimicina of the Old World to be generi- cally distinct from A. semialata and so retained it as Coridochloa cimicina (L.) Nees ex Jacks. Because the Kranz species of Alloteropsis have M.S. leaf anatomy whereas Coridochloa species are P.S., Ellis (in litt.) and I retain Coridochloa for the common Old World C. cimicina and the African C. quintasii (Mez) Pilger and C. paniculata (Benth.) Stapf. Most of the Kranz P.S. genera listed in Table 4 seem to form two natural and related groups, one of which can be called the Brachiaria group. In general, genera of this P.S. group have racemose in¬ florescences and rough (papillate to rugose) fertile lemmas, although in Brachiaria and some other genera there are species with smooth lemmas. This group also includes certain taxa often in¬ cluded in Panicum (groups k‘Fas- ciculata" and “Purpurascentia,” P. rep- tans L., etc.). Hsu (1965) and Stapf ( 1920) placed these in Brachiaria whereas Pilger (1940) included them in his subgenus U rochloides of Panicum. That this Brachiaria group is a natural one is sup¬ ported by the biochemical evidence that Brachiaria, Eriochloa, Urochloa, and “Fasciculata” are, uniquely and rather 24 THH KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS uniformly, PEP-ck (Gutierrez, Edwards, and Brown, 1976). Therefore, all species in Panic um that are P.S., PEP-ck should be removed and placed either in Brachiaria or elsewhere in that group. Dichanthelium has recently been ele¬ vated to generic rank (Gould, 1974). An extensive survey of 72 species has shown it to be a completely non-Kranz taxon (Brown and Smith, 1975) and therefore distinct from typical Panicum. Its trans¬ fer is also supported by this study and by the scanning electron microscope study of Clark and Gould (1975). A large number of Echinochloa species was studied because Hsu (1965) placed that taxon among the unspecialized (non-Kranz) genera. Also, Clark and Gould (1975) reported a marked differ¬ ence between it and typical Panicum in palea surface character. However, the whole genus seems to be Kranz M.S., the subtype typical of the tribe. Under the non-Kranz genus Ich- nanthus are listed three species that are Kranz. These, at least the Australian /. australiensis and /. pauciflorus, are ac¬ tually neither Panicum nor Ichnanthus (Lazarides, 1959), but have not been reassigned yet. Panicum majusculum and P . muelleri (Table 6), both also Kranz species from Australia, present problems of placement along with /. foliolosus, a Kranz species from Burma. Stieber (1975) considers that these five Kranz species form a taxon distinct from both Ichnanthus and Panicum , leaving /. vec- inus the sole Asiatic-African species in that genus, one closely related to the American /. pallens. Present evidence thus indicates that Ichnanthus is a com¬ pletely non-Kranz genus. Phanopyrum Nash has been retained for the unusual, non-Kranz American species usually treated as Panicum gym- nocarpon Ell. Within the large genus Setaria two problems were examined. It has already been established that some “typical” species of that genus are Kranz (Smith and Brown, 1973). However, it also in¬ cludes a number of wide- and plicate¬ leaved, shade-tolerant or shade-requiring species, the subgenus Ptychophyllum. Such species might be expected to be non-Kranz, but those examined (5. bar- bat a, S. chevalieri, S. membranifolia, S. palmifolia , S. panic ulif era , and S. poiretiana) are all Kranz. A very unusual shade-requiring genus, Microstegium, of the wholly Kranz Andropogoneae is also typically Kranz M.S., and M. vimineum is NADP-me and C4. Thus, as far as known, shade-requiring species of typi¬ cally Kranz taxa remain Kranz. (See Table 1 1 and further discussion under “The Andropogoneae”). The second problem in Setaria involves the subgenus Paurochaetium of Panicum. In 1910, Hitchcock and Chase proposed this subgenus for 8 to 10 Ameri¬ can species that have transversely rugose, apiculate lemmas, a bristle below the terminal spikelet on most branchlets ot the panicles, few-flowered slender in¬ florescences, and narrow leaves, and that are xerophytes of bright sunlight. Pilger (1940), Rominger (1962), and Hsu (1965) considered these to be species of Setaria. The present study supports that transfer because: groups of Kranz Panicum species with rough lemmas seem better included in other genera, and most Setaria species have rugose lemmas; and MEMOIRS OF THE TORREY BOTANICAL CLUB 25 the few groups in Panicum that have M.S. anatomy (“Agrostoidea," “Ten- era," and “Plena") are otherwise very distinct from Paurochaetium, whereas Setaria, like most genera of Paniceae, is also M.S. The only other alternative is to raise Paurochaetium to generic rank. Steinchisma Raf. was proposed for the single North American species generally designated as Panicum hians Elliott. Hitchcock and Chase (1910) proposed the informal group “Laxa" for 13 or more American species of Panicum usually characterized by spectacular enlarge¬ ment of lower sterile floret paleas. This group included P. hians and P. milioides (the latter from southern South America) of recent scientific prominence. Study of these two species (Brown and Brown, 1975) prompted a detailed investigation of that group. Hsu (1965) noted differences between Panicum hians and some other species of the group, notably that the fertile lemma is roughened by longitudinal rows of papillae, as illustrated by Clark and Gould ( 1975) for the palea. It is also true that two different sorts of inflorescence are present in the group. Condensed to open panicles are found in P. hians, P. milioides, P. cupreum, P. exiguiflorum, and P. decipiens, whereas P. la.xum and most of the other species have spikelets borne on essentially unilateral racemes. Correlated with the paniculate type are fertile florets with rows of papillae; with the unilaterally racemose type, smooth fertile florets. Since these are characters given very high priority in the Paniceae, I propose to segregate the P. hians assemblage in the genus Steinchisma (Table 3) and leave the P. la.xum assemblage in Panicum as the group “Laxa" (Tables 6, 7, and 8). These two taxa also differ in habit and habitat. Steinchisma comprises basically erect plants usually growing in full sun¬ light, whereas “Laxa" contains mostly prostrate plants growing in partial to heavy shade. It has recently been demonstrated that Steinchisma milioides and 5. hians have character states intermediate between those usually associated with C3 and C4 plants. Brown and Brown (1975) and Brown (in press) have shown that these species have intermediate leaf anatomy, mostly centripetal chloroplasts with numerous associated mitochondria, and intermediate photorespiratory effects. Ku, Edwards, and Kanai (in press), and Kanai and Kashiwagi ( 1975) have shown that they are intermediate in anatomy and biochemical activities of numerous C4 photosynthetic enzymes. Actually, S- h i a n s (Ell.) Nash ex Small and S. milioides are conspecific (as Arechavaleta, 1894, proposed) on the basis ot habit, spikelet and inflorescence characters, photosynthetic intermediacy, and flavonoids (author, unpublished). When the two are merged, the correct name under Steinchisma is S . hians. Leaf anatomy of the Mexican species Steinchisma cuprea seems to be typically non-Kranz, at least by the criteria of Hat- tersley and Watson (1976). That of S. e.x- igid flora from Cuba and Haiti appears to be kranz-like based on observation of embedded, stained sections, except that the walls of the “Kranz cells" are rela¬ tively thin. Details of the leaf anatomy of s- decipiens have not been studied. However, 13C/12C ratios of all species of 26 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS the genus are within the C3 range. It can be concluded, therefore, that S. exigui- flora should be intermediate between C3 and C4 types as is S. hians, but that S. cuprea can be expected to be rather typically C3. The monotypic Tarigidia aequiglumis Gossens may be a bigeneric hybrid of Anthephora pubescens Nees and a Digitaria species (Loxton, 1974). The work reported here complements that of Hsu (1965), who examined quite different characters — of lodicules, style bases, leaf epidermis, and especially fer¬ tile lemma epidermis — in about 40 genera of Paniceae, including 96 species of Panicum (including Dichanthelium). From his data he worked out a “speciali¬ zation index" based upon two or three alternative states for each character and upon assumptions as to which are most specialized (his Table 2). He then ar¬ ranged the various genera accordingly (his Figure 1 1). The main vertical separa¬ tion was: on the left, florets papillate or rugose; on the right, florets smooth or silicate. The main horizontal separation was: above, style bases united and lem¬ mas thinner; below, style bases distinct and lemmas firmer. Thus, his figure has four quarters as well as some minor sub¬ divisions. Table 5 is a modification of Hsu’s figure but maintains his basic plan. When the genera treated by Hsu are designated Kranz or non-kranz, as de¬ termined in this study, nearly all of those he placed in the lower right quarter and in the lower third of the lower left quarter are non-kranz. If subgenus Panicum and the genus Echinochloa are removed from his lower right quarter (they are both kranz), and non-kranz Hymenachne is brought down from the upper right to the lower right quarter, all non-kranz genera of Paniceae, including the subgenera Sarmentosum and Megathyrsum of Panicum, occupy the lower right quarter and the bottom of the lower left quarter. A line can then be drawn around all the non-kranz genera leaving all the kranz genera outside and above. According to Hsu’s scheme, the non- kranz, C3 genera are thus the least specialized. He considered this group of genera with low specialization indices as the origin of the variously more specialized groups. That implies, there¬ fore, that the kranz genera probably evolved from this non-kranz group. However, some kranz groups in Panicum and the kranz genus Echinochloa have Hsu specialization in¬ dices as low as those of any C3 genera. Evolutionary theory would also predict that the uncommon, biochemically and anatomically specialized kranz condition has evolved from the very common and less specialized non-kranz state. The correlation between my results and those of Hsu, based upon very differ¬ ent and unrelated criteria, is excellent and MEMOIRS OF THE TORREY BOTANICAL CLUB 27 TABLE 5. Genera of Paniceae , arranged according to a modification of Hsu's (1965) scheme. Numbers in parentheses are Hsu’s specialization indices for the taxa he studied. Lemmas rough Lemmas smooth C4. M.S., NADP-me C4 , M.S. and P S. Digitaria, Anthaenantia, Trichachne, Cenchrus, Pennisetum, Leptoloma (7-8), Leptocoryphium , Zygochloa, Thuarea, Leptosaccharum , Stereochlaena . Beckeropsis , Spinifex, Stenotaphrum , T rachys, Pseudoraphis, (5-8). Style bases united; lemmas thinner Lemmas rugose Style bases Lemmas papillate free; lemmas firmer C4, M S. Ixop horns (7) Seta ria (4-5) Setariopsis (4) Paspalidium (4) NADP-me Alloteropsis (5) Paspalum (4-5) Axonopus (4) Holcolemma Streptolophus C4, M S., NADP-me Echinochloa (2), Paratheria, Odontelytrum , Panicum — a few American groups C4, P S. Urochloa (4) Brachiaria (4) Pseudobrachia ri a Psilochloa Panicum, section Fasciculatum PEP-ck Chaetium (6) Eriochloa (4) Coridochloa Leucophrys Oryzidium Scutachne C4, P.S., NAD-me Panicum, subgenus Panicum. (1) c3 Hymenachne (6) Pseudechinolaena (6) Dichanthelium (5-7) Panicum, subgenus Sarmentosa (3-4) Sacciolepis (3) Oplis menus (2) Ichnanthus (2) A croc eras (2) Commelinidium ( 1 ) Lasiacis ( 1 ) Acritochaete Chloachne Microcalamus c, Ottochloa (4) Amphicarpum (4) Panicum , subgenus Megathyrsus (4) Neohusnotia (3) Cyrtococcum (3) En tolas ia Steinchisma THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS greatly strengthens his assumptions as to which conditions are to be considered un¬ specialized and which specialized. It can be proposed, therefore, that non-Kranz genera having style bases free and firm lemmas are the least specialized of the Paniceae. Another character Hsu considered significant in the Paniceae is the outer surface condition of the fertile florets, whether rough or smooth. The two alter¬ natives seem equally represented among both Kranz and non-Kranz types. If this character is highly significant, if one state has rarely evolved into the other, then it can be proposed that there are two paral¬ lel lines of evolution within the Paniceae, one with smooth and one with rough fer¬ tile florets. Most Kranz genera of Paniceae with less specialized inflorescences have style bases distinct and rough fertile florets, and are placed in Hsu's lower left quar¬ ter. Those with obvious specializations in the inflorescence (e.g., Stenotaphrum . Spinifex, C enchrus , Anthephora , Thuarea, Trachys, and Zygochloa) have style bases united and smooth fertile florets, and appear in the upper right quarter. Perhaps, then, with inflores¬ cence specialization fertile florets have become smooth and style bases have be¬ come united. The few genera in Hsu's upper left quarter, genera characterized by united style bases, thin fertile lemmas that are not inrolled, and rough fertile florets, are the clearly related Digitaria, Trichachne, Leptoloma, Anthaenantia , Lepto- coryphium, etc. (Stapf's subtribe Digitarianinae emended). Almost all P.S. genera occupy the middle of Hsu's lower left quarter (Urochloa, Brachiaria, Eriochloa, and Chaetium, studied by Hsu and me, as well as Coridochloa , Psilochloa, Leucophrys, Oryzidium, Scutachne , Pseudobrachiaria, and some sections of Panicum, studied by me). These genera are similar morphologically, anatomi¬ cally, and by Hsu’s specialization index. The highly specialized P.S. genera Spinifex and Thuarea were placed by Hsu in the upper right quarter, and the P.S., NAD-me species of Panicum are distinct (Figure 1). Figure 1 is an evolutionary scheme embodying major changes in arrange¬ ment of the Paniceae, based upon data from this study and the following assumptions. As generally accepted by agrostologists, racemose and more highly specialized inflorescences have evolved from the diffuse panicle, and the evolutionary tendency within the spikelet is from numerous florets toward one per spikelet. Evolution in leaf anatomy is from the general non-Kranz to the un¬ usual and more complex Kranz types. Evolution progresses from the simple, common, Calvin-Benson (C3) type of carboxylation to the biochemically un¬ usual and more complex C4 types. Of ap¬ parent necessity, these anatomical and biochemical characters have evolved to¬ gether. There is no good evidence that evolution from C4 to C3, Kranz to non- Kranz has ever occurred. In general, evolution of the Kranz syndrome in the Gramineae occurred a few times fairly early in the history of the family. This assumption is based on the fact that wholly Kranz grass taxa are often large, such as the Andropogoneae, many gen- MEMOIRS OF THE TORREY BOTANICAL CLUB 29 era of Paniceae, and the Eragrostoideae. Recent evolution of the syndrome would produce isolated species or genera that are partially kranz and partially non- Kranz, such as Chamaesyce (Webster, Brown, and Smith, 1975), Kallstroemia, Flaveria (Smith and Turner, 1975), Alternant hera, Mollugo, and in grasses. Allot eropsis semialata and the group “Grandia” of Panicum. The tropical, non-kranz, panicoid tribe Isachneae is characterized by hav¬ ing two similar, seed-producing, indu¬ rated florets per spikelet. Such a condi¬ tion is assumed to have been the evolutionary precursor of that found in the Paniceae. The latter typically have a single fertile floret per spikelet, a condi¬ tion which probably evolved rapidly to produce the original, tropical, paniculate, non-kranz Panicum (Figure I, number 10), undergoing only minor subsequent alteration. Like Isachne, these were species of moist, shady habitats, of tropi¬ cal forests and forest borders. They probably existed before the separation of Africa and South America and must have occurred in both areas. It has already been remarked (Chase, 1911) that some species of Isachne resemble the American genus Di- chanthelium, which may have evolved rather recently from some American species of the former, long after wide separation of the New and Old Worlds. FIGURE I. Evolutionary scheme of the Paniceae. l. 2. BRACH IARI A | GROUP K, P.S. 3. PANICUM K, P.S. N AD-me 4. PANICUM N panic-raceme 5. PANICEAE N •> — — • panic-raceme 6. PANICEAE K, M S. N A DP-me panic-receme- specialized k 9. PANICUM k, M S. r N ADP-me paniculate 7. PANICUM k. M S. N ADP-me paniculate paniculate t ISACHNE N paniculate 30 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS At some later time, some species of Panicum living in bright light evolved the Kranz syndrome with the M.S. type of leaf anatomy and the correlated NADP-me type of C4 photosynthesis (number 9). This M.S. type is the com¬ mon subsyndrome among the Kranz gen¬ era of Paniceae (Table 4) and occurs in all Andropogoneae. From a paniculate Panicum of this type the various modem genera of M.S. Paniceae have evolved (number 6). There are a few small groups of Panicum in America having this sub¬ syndrome also (number 7), and the two lines might be combined. Of course, there also must have been evolution from a non-Kranz Panicum type (number 10) to produce the numer¬ ous extant non-Kranz genera of Paniceae (number 5 and Table 4). A line of evolu¬ tion was also maintained leading to extant non-Kranz Panicum (number 4), which perhaps should be combined with the other non-Kranz Paniceae as one general “line” of evolution. At some time, in the evolutionary line of non-Kranz Panicum, some species evolved the P.S. type of anatomy and the associated aspartate type of C4 photosyn¬ thesis (number 8). From such a panicu¬ late Panicum have evolved, probably not at the same time, the typical modern NAD-me species of Panicum (number 3) and also the genera of the Brachiaria group that are characterized by PEP-ck photosynthesis and usually racemose in¬ florescences (number 1). Number 2 in Figure 1 designates any non-Panicum genera having P.S. anatomy and NAD- me photosynthesis, such as, possibly, Oryzidium , Chaetium, Scutachne , Thuarea, and Spinifex (Table 4). This scheme suggests that the obvi¬ ously heterogeneous Panicum is artificial and that all C3 taxa (number 4) and all Kranz M.S., NADP-me taxa (number 7) should be removed because the type species, P. miliaceum L., is Kranz P.S., NAD-me. It also suggests the transfer of any PEP-ck species, the group “Fas- ciculata” for example, to the Brachiaria group (number 1). The latter and Panicum (number 3) have morpholog¬ ical intermediates, Stapf’s section Eriochloideae (P. meyeranum), Pseu- dohrachiaria, and “Fasciculata,” but their type of C4 photosynthesis is dis¬ tinctive. When these taxa are placed in the Brachiaria group on that basis, the latter and Panicum become distinct and homogeneous. If the tribe is to be divided phylogeneti- cally into subtribes, it should be accord¬ ing to the foregoing scheme, assuming that leaf anatomy and photosynthesis types are indeed the best criteria for such subdivision. The following subtribal divi¬ sions (paralleling Table 4 and Figure 1) can be proposed. Subtribe 1. Paniculate mostly, Kranz M.S., C4 NADP-me. This taxon con¬ tains the largest number of genera and species (numbers 6 and 7, Figure 1 ; mid¬ dle column. Table 4). Subtribe 2. Non-Kranz, C3 (numbers 4 and 5, Figure 1; first column. Table 4). This is the second largest subtribe. Subtribe 3. B rachiariinae Butzin. Racemose, Kranz P.S., C4 PEP-ck. A smaller but substantial and widespread group of genera allied to Brachiaria (number 1, Figure 1; part of third column. Table 4). Subtribe 4. Panicinae Stapf. Panicu- MEMOIRS OF THE TORREY BOTANICAL CLUB 31 late, Kranz P.S., C4 NAD-me. As here circumscribed, this subtribe includes only the numerous species of Panicum allied to P. miliaceum, its type species (number 3, Figure 1). It should perhaps also include a few genera from the third column of Table 4, those excluded from Subtribe 3 (number 2, Figure I). Subtribes 1 and 2 are very distinct from one another and from the others on these criteria. Subtribes 3 and 4 are, however, less distinct from each other. Both are aspartate formers and have the same basic anatomy. It does seem likely that they differ generally in chloroplast loca¬ tion within the Kranz cells. In Panicum the chloroplasts are centripetal, whereas in the Brachiaria group they are cen¬ trifugal (Gutierrez, Gracen, and Ed¬ wards, 1974). These same two types of aspartate former have been reported in the Eragrostoideae, also wholly P.S. At this time it is not known how fundamental or trivial is the difference between the NAD-me and PEP-ck types of C4 photo¬ synthesis. As discussed earlier, there are a few possible exceptions to this scheme, one which assumes evolution of the Kranz syndrome two or three times during the early history of the tribe. The Australian non-Kranz Thyridolepis seems to be closely related to the Australian Kranz Neurachne and Paraneurachne, and the Australian non-Kranz Homopholis to the widespread Kranz Digitaria. These may represent two cases of more recent and independent evolution of the Kranz syn¬ drome. Even more suggestive that evolu¬ tion of the syndrome may have occurred very recently, in addition to early in the history of the tribe, is the previously dis¬ cussed case of Alloteropsis semialata/A . eckloniana, in which both the Kranz and non-Kranz types are morphologically al¬ most indistinguishable and possible in¬ termediates occur in South Africa (Ellis, 1974b). There are also two other possible cases of recent evolution from non-Kranz to Kranz, within the “Grandia” group of Panicum and the Australian genus Neurachne. Nevertheless, in spite of such expected exceptions, the assump¬ tion that the Kranz syndrome did evolve a few times during the early evolution of the tribe remains acceptable. Because the only grasses with M.S. leaf anatomy are the Andropogoneae and most of the Kranz Paniceae, and because these two tribes are related by spikelet characteristics, it seems evident that the recent Andropogoneae (Hartley, 1958a) evolved from some ancient M.S. Paniceae or, at least, Panicoideae. It has been stated (Downton, 1971b) that the Kranz syndrome is an evolutionary adaptation to arid environ¬ ments. There are, of course, Kranz species in arid regions, but there are many more in mesic areas. Among the Paniceae it is probably true that some Kranz species occupy drier habitats than do any non-Kranz species. But there are numerous Kranz species which grow in very wet places (in Echinochloa, Pas- palum, Axonopus , Oryzidium . and Paspalidium ), and there are non-Kranz species of dry habitats (in Cleistochloa, Dichanthelium, Dimorphochloa , Thyridolepis, and Ichnanthus). The generalization that Kranz species are tropical has often been made, with the implication that non-Kranz species are not. Among the Paniceae both types ex- 32 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS tend over approximately the same latitud¬ inal range, from about 45° N to 45° S. In North America, though both non-Kranz ( Dichanthelium ) and Kranz ( Panic um, Echinochloa, Paspalum, Setaria, etc.) types extend about equally far north, many more Kranz species do so. Full sunlight seems to be necessary for most Kranz species, except some in Chamaesyce ( Euphorbia ) and Setaria, and all of Microstegium (Andro- pogoneae). On the other hand, non- Kranz species tolerate light intensities ranging from deep shade in tropical forests to full sunlight in open tropical and subtropical habitats. Of course, non-Kranz species of the Festuceae, etc. range into arctic and alpine regions where no Kranz species occur, and some species of Bambuseae, Oryzeae, etc. do grow in full tropical sunlight. In warm temperate regions where the ground does not freeze during the winter, the non-Kranz festucoid grasses grow during the winter and early spring, whereas in late summer and early fall nearly all growing grasses are Kranz or else are non-Kranz species of sub¬ families represented mainly in hot re¬ gions ( Panicoideae, Eragrostoideae, Oryzoideae). That is, C3 grasses of high latitude origins can and do grow during the winter in warm temperate regions, whereas C3 and C4 grasses of low latitude origins seem unable to do so. The climatic restrictions are thus independent of C3/C4 character. PAN 1C UM It has been well established that within the genus Panicum all basic types of leaf anatomy and correlated types of photo¬ synthetic systems occur (Downton, Berry, and Tregunna, 1969; Smith and Brown, 1973; Guteirrez, Gracen, and Edwards, 1974), just as they all occur among the rest of Paniceae. Because basic type of leaf anatomy, Kranz or non-Kranz, was the major basis for sys¬ tematic revision elsewhere in the Gramineae between 1931 (Avdulow, 1931) and 1961 (Stebbins and Crampton, 1961), it seems likely that this criterion might be equally significant in the sys- tematics of Panicum. Accepting the assumptions previously discussed, these types characterize four distinct groups of related species within Panicum. However, if C3 to C4 evolution took place long ago and a number of times within the Gramineae, as seems likely, it is also possible that there is something about grasses that predisposes them to evolution of the Kranz syndrome. There¬ fore, less ancient and even quite recent evolution of C4 photosynthesis cannot be ruled out. There exists also the possibility of reverse evolution, from C4 to C3. However, rigorous proof that evolution did indeed go in that direction is de¬ manded. Hsu (1965) employed quite different characters in his study and classifications of the Paniceae and Panicum. Perhaps the most meaningful character he used was the cellular appearance of the fertile lemma surfaces as seen under high mag¬ nification of a compound microscope. The nearest the present study ap¬ proached Hsu’s was examination of fer¬ tile lemma surfaces under high power of a dissecting microscope, as utilized MEMOIRS OF THE TORREY BOTANICAL CLUB 33 routinely by taxonomists. The only species examined in this way were those of unknown sections and a few others. Hsu grouped sections within subgenera at least in part on this character. Of course it is well known that within genera (e.g., Setaria, Brachiarici) these surfaces can range from very rugose to smooth, so this character should be utilized in sys- tematics with caution, though it must cer¬ tainly be employed in such studies. Throughout its taxonomic history gen¬ era have constantly been removed from Pcinicum, and yet it remains very large and heterogeneous. Since about 1900, taxonomists have erected many new gen¬ era and subdivided what remains of Panicum into groups or sections of ap¬ parently related species. Hitchcock and Chase (1910) divided the North Ameri¬ can species into a number of informal groups. Stapf (1920) subdivided the species of tropical Africa into formal sec¬ tions. Pilger (1940) treated the genus on a world-wide scale, subdividing it into for¬ mal sections. Hsu (1965) sampled a few species each from most of the accepted sections for selected characters — of lodicules, fertile lemma surface, styles, etc. — and arranged the sections accord- ingtolevel of “specialization index”. His treatment was about the only one of these that implied an evolutionary scheme. Because of its heterogeneity and its in¬ terrelationships with other genera, Panicum can hardly be treated apart from the tribe (Hsu, 1965) (Figure 1). There¬ fore, this study included an almost com¬ plete survey of the genera of the tribe and examination of about half the species of Panicum, representing all proposed groups and sections except a small (three species) section of Pilger's (1940), Pseudolasiacis, from Madagascar. TABLE 6. Species of Panicum examined, arranged alphabetically: anatomical and photosynthetic characters . provenances, and voucher herbaria. Numbers in parentheses indicate numbers of specimens ex¬ amined if more than one. Synd. 8|:'C Anat. Prov. Herb. abscission (2) Ka MS. U.S.A. TEX adenophorum Nar -22.4 Africa US ads persimi Ka PS. S. Am. TEX aequi nerve Nr -26.7 Africa PRE afzelii Ka PS. Africa US a gro st aides Kar - 14.1 MS. USA. TEX alt am Ka PS. Mexico TEX a ma nil am (4) Kar -1 1.4 PS. U.S.A. TEX anceps Kar -1 1.8 MS. USA. TEX andringitrense Na Africa US antidotale ( S ) Kar -14. 1 M.S. India TEX aphanoneurum (2) Ka PS. Africa US. TEX THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 6 continued. Synd. 813C Anat. Prov. Herb. aquaticum (3) Kar - 12.2 P.S. S. Am. TEX arcurameum Ka P.S. Africa US arizonicum Kar -11.5 P.S. U.S.A. TEX arbusculum Ka P.S. Africa PRE atrosanguineum (3) Ka P.S. Africa US auritum Nr -27.7 Asia US australiensis (2) Kar -13.0 P.S. Aust. NSW, TEX bartlettii (2) Nr -28.3 C. Am. TEX bartowense Kar -14.4 P.S. U.S.A. TEX beccabunga Na Africa US beecheyi Kar -12.7 P.S. Hawaii US bergii Kar — 12.2 P.S. U.S.A. TEX biglandulare (2) Nr -27.4 S. Am. US. TEX bisulcatum Nr -24.3 Asia TEX boliviense (2) Nr -26.2 S. Am. US, TEX brachyanthum Nr -28.3 U.S.A. TEX brevifolium Na Africa US bulbosum Ka MS. U.S.A. TEX buncei (3) Kar -13.1 P.S. Aust. NSW, TEX calvum (2) Na Africa US, TEX ccimbogiensis Ka P.S. Asia US cap ilia re Ka P.S. U.S.A. TEX capillarioides Ka P.S. Mexico TEX capillipes Ka P.S. Aust. TEX caricoides Kar -14.0 MS. Cuba TEX caudiglume Na Africa US cayennense Ka P.S. Mexico TEX cervicatum Kar -13.6 P.S. S. Am. US chase i Ka P.S. S. Am. TEX chionachne Na Africa TEX chusqueoides Kar -13.6 P.S. Africa PRE cinereum Kar -1 1.4 P.S. Hawaii US colliei Kar -12.1 P.S. Hawaii US co to rat am (3) Ka P.S. Africa TEX cupressifolium Nar -27.6 Madag. US cyanescens Nar -27.6 S. Am. US cynodon Nar -25.9 Hawaii US cyrtococcoides Nr -29.8 Africa US decolorans (2) Kar -12.7 P.S. Mexico TEX decomposition (2) Kar - 12.2 P.S. Aust. NSW. TEX dens tarn (2) Kar -11.9 P.S. Africa PRE, TEX dichotomiflorum (3) Kar -14.1 P.S. U.S.A. TEX diffusion Ka P.S. Mexico TEX di sere pans (5) Kar -13.5 MS. Cuba US, TEX dregeanum Kar -12.3 P.S. Africa PRE echinulatum Ka P.S. S. Am. TEX MEMOIRS OF THE TORREY BOTANICAL CLUB 35 Table 6 continued. Synd. 513C Anat. Prov. Herb. ecklottii Nar -24.4 Africa PRE effusum kar -12.6 PS. Aust. NSW elephantipes (3) Kar -14.2 P.S. S. Am. US, TEX exiguum ka P.S. S. Am. TEX fasciculatum kar -13.0 P.S. USA. TEX fauriei kar -10.9 P.S. Hawaii US filipes ka P.S. US. A. TEX flexile ka P.S. U.S.A. TEX fluviicola ka P.S. Africa US foliolosum kr -12.0 Asia kEW foliosum ka P.S. Aust. TEX frederici Nr -24.6 Africa US frondescens (2) Nar -32.4 S. Am. US. TEX fulgens Na Africa US fulgidum (2) kar -12.1 P.S. Aust. NSW, TEX gardneri Nr -31.4 S. Am. US gattingeri ka P.S. U.S.A. TEX genuflexum ka P.S. Africa US ghiesbregtii (3) ka P.S. Mexico TEX glabrescens (2) ka P.S. Africa PRE. TEX glabripes ka P.S. S. Am. TEX glutinosum (2) Nar -26.8 S. Am. US, TEX gouini ka P.S. Mexico TEX gracilicaule Nr -29.6 Africa US griff onii (2) ka P.S. Africa TEX grande (2) Nar 1 00 S. Am. US, TEX gr a mo sum (2) Nr -25.6 S. Am. US, TEX gymnocarpon (3) Nar -29.1 U.S.A. TEX guianense Nr -24.0 S. Am. US haenkeanum (2) Nar -28.0 S. Am. US. TEX hallii kar -13.4 P.S. U.S.A. TEX havardii ka P.S. U.S.A. TEX helobium (2) Nar -27.9 S. Am. TEX heterostachyum (2) Nr -30.5 Africa PRE, TEX hillmanii ka P.S. U.S.A. TEX hippothrix (2) ka P.S. Africa US. TEX hirsutum ka P.S. S. Am. TEX hirticaule (2) ka P.S. Mexico, Texas TEX hirtum (3) Nar -30.7 W. Indies US, TEX hochstetteri (2) Na Africa US. TEX humile kar - 9.5 P.S. Asia US hygrocharis ka P.S. Africa US hymeniochilum Nr -26.8 Africa PRE hystrix Na Africa US ianthum Na Africa US THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 6 continued. Synd. 813C Anat. Prov. Herb. ichnanthoides ka PS. S. Am. TEX infestum Ka P.S. Africa US kaalense Ka P.S. Hawaii TEX kalahariense Kar -13.8 P.S. Africa PRE kerstingii (2) Ka P.S. Africa US, TEX koolauense Na Hawaii TEX lachnophyllum (2) Nar -23.3 Aust. NSW, TEX laetum Ka P.S. Africa US laevifolium (2) Kar -12.1 P.S. Africa PRE, TEX la c us t re Ka P.S. Cuba TEX laxum (2) Nar -25.8 Mexico TEX lepidulum Ka P.S. Mexico TEX leium Na C. Am. TEX lineatum Nar -29.5 Africa US longijubatum Ka P.S. Africa US longum Nr -27.9 S. Am. US lundellii Ka P.S. Mexico TEX longifolium Ka MS. U.S.A. TEX majusculum (2) Kar -12.0 P.S. Aust. NSW, US maximum (3) Kar -13.3 P.S. Africa TEX mertensii (2) Nr -29.5 C. Am. US, TEX meyerianum Kar -12.3 P.S. Africa PRE microthyrsum Na Africa US miliaceum (3) Kar -16.0 P.S. India US, TEX micranthum Na W. Indies TEX milleflorum (2) Nr -27.1 S. Am. US, TEX mindansense Kar -10.6 P.S. Aust. NSW mode (2) Ka P.S. Mexico TEX monticolum (2) Nar -31.1 Africa PRE, TEX montanum Na India TEX muelleri Kr -13.2 Aust. US natalense Nar -23.8 Africa PRE neglectum (2) Kar -12.4 P.S. Africa US, TEX nephelophilum (2) Kar -1 1.4 P.S. Hawaii US. TEX nervosum Na W. Indies TEX novemnerve (2) Kar -1 1.5 P.S. Africa PRE, TEX nubigenum Ka P.S. Hawaii TEX obseptum Kar -17.5 P.S. Aust. NSW obtusum Kar -12.7 MS. U.S.A. TEX ova life rum Na S. Am. TEX paludosum (8) Kar -12.8 P.S. Aust., As. NSW, US pampinosum Ka P.S. U.S.A. TEX pantrichum Nr -30.4 Mexico US parcum Ka P.S. Mexico TEX MEMOIRS OF THE TORREY BOTANICAL CLUB 37 Table 6 continued. Synd. 8' 3 C Anat. Prov. Herb. parvifolium (2) Nar -31.1 Africa, S. Am. PRE. TEX parviglume (2) Nar — 29.2 S. Am. US, TEX pauciflorum kr -11.8 Aust. US paucispicatum kar -11.6 PS. S. Am. TEX pectination Nr -26.4 Africa US pectinellum Na Africa US pellitum Kar - 12.8 PS. Hawaii US penicillatum Na S. Am. TEX petersonii (2) kar -17.0 M.S. Cuba TEX philadelphicum ka P.S. U.S.A. TEX pilcomayense ka PS. S. Am. TEX pilosum (4) Nar -28.1 S. Am. TEX pinifolium kar -12.4 P.S. Africa TEX, US plenum (2) kar -11.9 MS. U.S.A. TEX polygonaturn (3) Nar -28.5 C. Am. TEX porphyrrhizos (2) ka P.S. Africa US. TEX prialtum Na Africa US prionitis kar -12.0 M.S. S. Am. US procurrens (2) Nar 1 to 00 -o S. Am. US, TEX pro hit tan Nar -25.9 Aust. NSW psilopodium ka India TEX pterigodium Na S. Am. TEX pubiglume Nr 1 to -a b Africa US pulchellum (3) Nar -30.4 Mexico US, TEX pus ilium (2) Nar -26.8 Africa US, TEX pygmaeum (3) Nar -29.7 Aust. NSW, TEX pyrularium Nr -29.4 S. Am. US quadriglume Ka P.S. S. Am. TEX queenslandicum kar -12.0 P.S. Aust. NSW racemosum (2) kar -11.3 P.S. S. Am. US, TEX rectissimum Na S. Am. TEX re pens (2) kar -12.3 P.S. America TEX rhizomatum kar -12.9 M.S. U.S.A. TEX rigidulum (2) ka M.S. U.S.A. TEX ri vula re Na S. Am. TEX robynsii Na Africa US rowlandii ka P.S. Africa US rudgei (2) kar -14.5 P.S. S. Am. US. TEX rugulosum (5) Nar -29.0 S. Am. TEX schiffneri (3) Nar -28.6 S. Am. US, TEX schinzii ka P.S. Africa US schmitzii (2) Nar -26.8 S. Am. US, TEX sciurotis (2) Nar -27.9 S. Am. US, TEX sellowii (2) Nr -28. 1 S. Am. US, TEX seminudum kar -12.3 P.S. Aust . NSW 38 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 6 continued. Synd. S13C Anat. Prov. Herb. snowdenii Na Africa US sonorum Ka P.S. Mexico TEX spathellosum Nar S. Am. TEX s per guli folium Na Africa US stagnatile (4) Na C. Am. TEX stapfianum (2) Ka P.S. Africa PRE, TEX stenodes (2) Kar -11.6 M.S. S. Am. TEX stenodoides Ka M.S. C. Am. TEX stevensianum (2) Nar -25.2 S. Am. US. TEX stipitatum Ka M.S. U.S.A. TEX stoloniferum (3) Nar -36.7 S. Am. US, TEX stramineum Ka P.S. Mexico TEX subalbidum Kar -11.4 P.S. Africa US subflabellatum Ka P.S. Africa US sublaetum Nr -25.6 Africa US sucosum Ka P.S. Mexico TEX subxerophilum Nar -25.8 Aust. NSW tamaulipense Ka P.S. Mexico TEX tenerum (3) Kar -1 1.4 M.S. U.S.A. TEX tenuifolium (2) Kar -11.5 P.S. Hawaii US, TEX texanum Ka P.S. U.S.A. TEX torridum (2) Kar -12.1 P.S. Hawaii US. TEX trachyrachis Kar -13.3 P.S. Aust. NSW transiens Na Mexico TEX transvenulosurn Na Africa US trichanthum (2) Nar -28.4 C. Am. TEX trichocladum (3) Ka P.S. Africa US, TEX tricholaenoides Ka P.S. S. Am. TEX trichoides (3) Nar -25.3 World TEX trigonum Na Asia TEX tuckermani Ka P.S. U.S.A. TEX tuerckheimii (3) Kar -13.5 M.S. C. Am. US, TEX turgidum Kar -12.7 P.S. Africa US umbellatum Kar -10.7 P.S. Africa US urvilleanum (3) Kar -12.1 P.S. U.S.A. TEX uvu latum Nr -28.6 Madag. US vaseyanum Ka P.S. Mexico TEX venezuetae Na Cuba TEX verrucosum Nr -25.6 U.S.A. TEX virgatum Kar -11.7 P.S. U.S.A. TEX virgultorum (2) Na Mexico TEX voeltzkowii Kar -12.6 P.S. Madag. US whitei Kar -13.3 P.S. Aust. NSW xerophilum Ka P.S. Hawaii TEX yavit aense Nr -30.1 S. Am. US Totals: N = 100; P.S. = 117; M.S.=20. MEMOIRS OF THE TORREY BOTANICAL CLUB 39 Table 6 lists alphabetically the 241 species examined from the world dis¬ tribution of the genus, but mostly from tropical Africa and America, the regions of greatest abundance (Hartley, 1958b). The selection of species was determined in part by an attempt to sample all previ¬ ously proposed groups and sections, in part by availability, and in part by an ef¬ fort to find non-Kranz species. This large world-wide sample seems to be represen¬ tative enough for sound general conclu¬ sions about the genus. Of the species examined, 104 are non-Kranz and 137 are Kranz. This list does not include 72 species of Dichanthelium usually included in Panicum, all of which are non-Kranz (Brown and Smith, 1975) and have been segregated from it (Gould, 1974). Of this sample, 57 percent are Kranz and 43 per¬ cent are non-Kranz. Thus, probably, somewhat more than 50 percent of all Panicum species are Kranz. It is also evident from Table 6 that the Kranz species fall in both the M.S. and P.S. classes of leaf anatomy, with P.S. species being by far the more numerous. Furthermore, all the M.S. species are American except the Asiatic Panicum antidotale . Whereas the majority of Kranz species of Panicum are P.S., a majority of Kranz Paniceae are M.S. (Table 4). A deliberate attempt was made to ex¬ amine species from all groups and sec¬ tions of Hitchcock and Chase (1910), Stapf (1920), Pilger (1940), and Hsu (1965). When all examined species were assigned as far as possible to their proper taxa, it became evident that nearly all such named groups are homogeneously Kranz or non-Kranz, P.S. or M.S. Sec¬ tion Clavelligera Stapf is all non-Kranz except for Panicum deustum. Group ‘ Maxima" Hitch, and Chase, as treated by Hsu (1965), is obviously artificial, ac¬ cording to these criteria, by inclusion of non-Kranz P. trichocladum, Kranz M.S. P. bulbosum and P. plenum , and P. max¬ imum that is Kranz P.S. and PEP-ck. And P. antidotale, which is Kranz M.S., is out of place among the non-Kranz species of section Sarmentosa Pilger. Table 7 reflects an effort to make all sec¬ tions and groups homogeneous for these characters. As used here these taxa are tentative, in the sense of Hitchcock and Chase (1910). Some of them deserve for¬ mal recognition but others do not. Those not already named formally should re¬ main informal until a detailed study of all species of the world is completed, em¬ ploying all available evidence. It is assumed that leaf anatomical characters are, in general, more funda¬ mental and conservative than the mor¬ phological ones (other than the very con¬ servative basic spikelet plan of the Paniceae). I thus propose to modify any sections or groups that are heterogene¬ ous, making each uniformly Kranz or non-Kranz. Furthermore, among the Kranz taxa it is proposed to make each uniformly M.S. or P.S., and among the Kranz P.S. species to segregate where possible the few known to be PEP-ck and their obvious allies from the NAD-me species at the subgeneric or generic level. All non-Kranz taxa are also segregated in separate subgenera or genera. The wholly non-Kranz subgenus Dichanthelium (Brown and Smith, 1975) has been raised to generic rank (Gould, 4U THE KRANZ S\ N DROME AND ITS SUBTYPES IN GRASS SYSTEMATICS 1974) and that change is supported by Species of that genus are not included in Clark and Gould ( 1975) and by this study. Tables 6, 7, or 8. TABLE 7. Species of Panicum examined, arranged by supraspecific taxa: anatomical and photosynthetic characters, provenances, voucher herbaria, and basic chromosome numbers, if known. Synd. 813C Anat. Prov. Herb. I. Subgenus PANICUM (x=9) 1. Section Panicum (x = 9) ahum Ka P.S. C. Am. TEX amarulum Ka P.S. USA. TEX arcurameum Ka P.S. Africa US atrosanguineum Ka P.S. Africa US beecheyi Kar -12.7 P.S. Hawaii US cambogiense Ka P.S. Asia US cap ilia re Kar -14.3 P.S. U.S.A. TEX cayennense Ka P.S. Mexico TEX cinereum Kar -11.4 P.S. Hawaii US colliei Kar -12.1 P.S. Hawaii US decolorans Kar -12.7 P.S. Mexico TEX effusum Kar -12.6 P.S. Aust. NSW fauriei Kar -10.9 P.S. Hawaii US flexile Ka P.S. U.S.A. TEX gattingeri Ka P.S. U.S.A. TEX havardii Ka P.S. U.S.A. TEX hillmanii Ka P.S. U.S.A. TEX hippothrix Ka P.S. Africa US hirticaule Ka P.S. U.S.A. TEX humile Kar - 9.5 P.S. Asia US ichnanthoides Ka P.S. C. Am. TEX kaalense (2) Ka P.S. Hawaii TEX kerstingii (2) Ka P.S. Africa US, TEX laetum Ka P.S. Africa US lundellii Ka P.S. C. Am. TEX miliaceum (3) Kar -16.0 P.S. Asia US, TEX nephelophilum (2) Kar -1 1.4 P.S. Hawaii US, TEX novemnerve Kar -11.5 P.S. Africa PRE nubigenurn (2) Kar -11.7 P.S. Hawaii US, TEX pampinosum Ka P.S. U.S.A. TEX pare am (2) Ka P.S. Mexico US, TEX pellitum Kar -12.8 P.S. Hawaii US ph iladelphicum Ka P.S. U.S.A. TEX sonorum Ka P.S. Mexico TEX stramineum Ka P.S. Mexico TEX MEMOIRS OF THE TORREY BOTANICAL CLUB 41 Table 7 continued. Synd. 513C Anat. Prov. Herb. tenuifolium (2) kar -11.5 PS. Hawaii US, TEX torridum (2) kar -12.1 PS. Hawaii US, TEX trachyrachis ka PS. Aust. NSW tuckermani ka PS. U.S.A. TEX virgatum kar -11.7 P.S. U.S.A. TEX Group “ Dichotomiflora" (x=9) bartowense kar -14.4 P.S. U.S.A. TEX coloratum ka P.S. Africa TEX dichotomiflorum kar -14.1 P.S. U.S.A. TEX hygrocharis ka P.S. Africa US kalahariense kar -13.8 P.S. Africa PRE laevifolium (2) kar -12.1 P.S. Africa PRE, TEX longijubatum ka P.S. Africa US porphyrrhizos (2) ka P.S. Africa US, TEX schinzii ka P.S. Africa US stapfianum ka P.S. Africa TEX sabalbidum kar -11.4 P.S. Africa US sucosum ka P.S. Mexico TEX vaseyanum ka P.S. Mexico TEX Section Repentia ( x =9) aquaticum (2) kar -12.2 P.S. S. Am. TEX decompositum kar - 12.2 P.S. Aust. US gouini (2) ka P.S. Mexico TEX locust re ka P.S. Cuba TEX paludosum (8) kar -16.6 P.S. As, Aust. NSW, US pinifolium kar -12.4 P.S. Africa US repens (3) kar -12.3 P.S. World TEX subflabellatum ka P.S. Africa US Group “Diffusa” ( x =9) afzelii ka P.S. Africa US aphanoneurum ka P.S. Africa US bergii kar -12.3 P.S. S. Am. TEX capillarioides ka P.S. Mexico TEX chase i ka P.S. S. Am. TEX diffusion ka P.S. Mexico TEX drege anion kar -12.3 P.S. Africa PRE filipes ka P.S. U.S.A. TEX fluviicola ka P.S. Africa US genuflexion ka P.S. Africa US ghiesbregtii (3) ka P.S. Mexico TEX griffonii ka P.S. Africa US hallii kar -13.4 P.S. U.S.A. TEX hirsutum ka P.S. C. Am. TEX lep id ulum ka P.S. Mexico TEX THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 7 continued. Synd. gl3C Anat. Prov. Herb. pilco may e rise (2) Ka P.S. S, N. Am. TEX rowlandii Ka P.S. Africa US quadriglume Ka P.S. S. Am. TEX tamaulipense Ka P.S. Mexico TEX 5. Group "Rudgeana” (x =9) rudgei Kar -14.5 P.S. S. Am. US, TEX 6. Section Dura (x=9) neglectum (2) Kar -12.4 P.S. Africa US, TEX race mo sum Kar -11.3 P.S. S. Am. US turgidum Kar -12.7 P.S. Africa US urvilleanum Kar -12.1 P.S. America TEX Miscellaneous "true” panicums. arbusculum Ka P.S. Africa PRE buncei (3) Kar -13.1 P.S. Aust. NSW, TEX cervicatum Kar -13.6 P.S. S. Am. US exiguum Ka P.S. S. Am. TEX fulgidum (2) Kar -12.1 P.S. Aust. NSW. TEX glabripes Ka P.S. S. Am. TEX nubigenum Ka P.S. Hawaii TEX obseptum Kar -17.5 P.S. Aust. NSW psilopodium Ka P.S. India TEX queenslandicum Kar -12.0 P.S. Aust. NSW seminudum Kar -12.3 P.S. Aust. NSW tricholaenoides Ka P.S. S. Am. TEX voeltzkowii Kar -12.6 P.S. Madag. US whitei (2) Kar -13.3 P.S. Aust. NSW, TEX x erophilum Ka P.S. Hawaii TEX P.S. species of doubtful position or not Panicum deustum (2) Kar -11.9 P.S. Africa PRE, TEX elephantipes (3) Kar -14.2 P.S. S. Am. US, TEX glabrescens (2) Ka P.S. Africa PRE, TEX trichocladum (3) Ka P.S. Africa US. TEX umbellatum Kar -10.7 P.S. Africa US chusqueoides (like Brachiaria) P.S. Africa PRE echinulatum — Brachiaria echinulata (Mez) Parodi S. Am. TEX infestum (like Brachiaria ) P.S. Africa US maximum (like Brachiaria) P.S. Africa TEX meyerianum (2) = Eriochloa meyeriana (Nees) Pilger P.S. Africa PRE, TEX Group "Fasciculata” (All Brachiaria) adspersa (Trin.) Parodi P.S. S. Am. TEX arizonica (S. and M.) S. T. Blake U.S.A. TEX MEMOIRS OF THE TORREY BOTANICAL CLUB 43 Table 7 continued. Synd. 813C Anat. Prov. Herb. fasciculata (Sw.) Parodi P.S. U.S.A. TEX mollis (Sw.) Parodi P.S. C. Am. TEX ramosa Stapf P.S. Asia TEX reptans (L) Gardn. and Hubb. P.S. World TEX texana (Buckl.) S. T. Blake P.S. U.S.A. TEX. Ichnanthoid group australiensis (2) -13.0 P.S. Aust. TEX, NSW folio sum Kr -12.0 P.S. Asia K majusculum (2) Kar © ri 1 P.S. Aust. NSW, US nine lie ri Kr -13.2 Aust. US pauciflorum Kr -11.8 Aust. US II. Miscellaneous M.S . Assemblage (x = 9,10) 7. Group “Agrostoidea” (x=9) abscission Ka MS. U.S.A. TEX agrostoides Kar -14.1 MS. U.S.A. TEX anceps Kar -1 1.8 M.S. U.S.A. TEX longifolium Ka M.S. U.S.A. TEX rhizomatum Kar -12.2 M.S. U.S.A. TEX rigidulum Ka M.S. U.S.A. TEX stipitatum Ka M.S. U.S.A. TEX 8. Group “Tenera” (x = 10) caricoides Ka -14.0 M.S. Cuba TEX stenodes Kar -11.6 M.S. S. Am. TEX stenodoides Ka M.S. C. Am. TEX tenerum Kar -11.4 M.S. U.S.A. TEX 9. Group “Plena” (x = 9) antidotale (3) Kar -14.1 M.S. India TEX bulbosum Ka M.S. U.S.A. TEX plenum (2) Kar -1 1.9 M.S. U.S.A. TEX 10. Group “Obtusa” (x= 10) obtusion Kar -12.7 M.S. U.S.A. TEX 11. Group “Discrepantia” (x = ?) discrepans (5) Kar -13.5 M.S. S. Am. US. TEX 12. Group “Tuerckheimiana” (x = ?) tuerckheimii (2) Kar -13.5 M.S. S. Am. US, TEX 21. Group “Grandia” (pars) (x=10) petersonii (2) Ka M.S. Cuba TEX prionitis Kar -12.0 M.S. S. Am. US 44 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 7 continued. Synd. 8I3C Anat. Prov. Herb. III. Subgenus SARMENTOSUM (x=9,10) 13. Group “Haenkeana” (x= 10) haenkeanum (2) Nar -28.0 C. Am. US, TEX 14. Group “Megista” (x = 10) mertensii (2) Nar -29.5 S. Am. US, TEX 15. Group “Parviglumia” ( x = 9) parviglume Nr — 29.2 S. Am. US schiffneri Nr -28.6 S. Am. US schmitzii (2) Nar -26.8 S. Am. US, TEX virgultorum Na Mexico TEX 16. Group “Parvifolia” (x=9) cyanescens Nar -27.6 S. Am. US nervosa Na S. Am. TEX parvifolium (2) Nar -31.1 Africa PRE, TEX 17. Section Pus ilia (x = ?) beccabunga Na Africa US pus ilium (2) Nar -26.8 Africa US, TEX 18. Section Sannentosa ( x =9) bisulcatum Nr -24.3 Asia TEX glutinosurn Nar -26.8 S. Am. US montanurn Na India TEX rugulosum (5) Nar — 27.2 S. Am. TEX sellowii (2) Nar -28.1 S. Am. US, TEX 19. Group “Stolonifera" (x = 10) biglandulare Nr -27.4 S. Am. US frondescens Nr -32.4 S. Am. US pulchellurn Nr -30.4 Mexico US stoloniferum Nr -36.7 S. Am. US 20. Section Trinerves (x = ?) caudiglume Na Africa US microthyrsum Na Africa US 21. Group “Grandia” (pars) (x = 10) grande (2) Nar -28.3 S. Am. US, TEX grumosum (2) Nar -25.6 S. Am. US, TEX rivulare Na S. Am. TEX stagnatile (4) Na S. Am. TEX Miscellaneous andringitrense Na Africa US auritum Nr -27.7 Asia US cyanescens Nar -27.6 S. Am. US cynodon Nar -25.9 Hawaii US MEMOIRS OF THE TORREY BOTANICAL CLUB 45 Table 7 continued. Synd. S,3C Anat. Prov. Herb. hymeniochilum Nr -26.8 Africa PRE koolanense Na Hawaii TEX leium Na C. Am. TEX micranthum Na W. Ind. TEX prolutum Nar -25.9 Aust. NSW pterigodium Na S. Am. TEX pygmaeum (3) Nar -29.7 Aust. NSW, TEX rectissimum Na S. Am. TEX sciurotis Nr -27.9 S. Am. US transiens Na Mexico TEX transvenulosum Na Africa US uvulatum Nr -28.6 Madag. US venezuelae Na Cuba TEX yavitaense Nr -30.1 S. Am. US Group “Laxa” ( x = 10) boliviense Nr -26.2 S. Am. TEX guianense Nr -24.0 S. Am. US lax urn Nr -24.0 C. Am. US longum Nr -27.9 S. Am. US rnilleflorurn Nr -27.1 S. Am. US pilosum (2) Nar -27.8 S. Am. US, TEX polygonatum (2) Nar -28.4 S. Am. US. TEX stevensianum Nr -25.2 S. Am. US IV. Subgenus MEGATHYRSUS (x=9,10) Section Clavelligera (x = ?) adenophorum Nr -22.4 Africa US tine at urn Nar -29.4 Africa US Section Pectinata (x=9) ecklonii Nr -24.4 Africa US, PRE pectinatum Nr -26.4 Africa US pectinellum Na Africa US Section Monticola (x=9 and/or 10) calvurn (2) Na Africa US hochstetteri Na Africa US rnonticolurn Nar -31.1 Africa PRE, US natalense Nr -23.8 Africa PRE Group “Trichoidea’' (x=9) aequinerve Nr -26.7 Africa PRE brevifolium Na S. Am. US chionachne Na S. Am. US cyrtococcoides Nr -29.8 Africa US gardneri Nr -31.4 S. Am. US 46 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 7 continued. Synd. 813C Anat. Prov. Herb. helobium (2) Nar -27.9 S. Am. US, TEX heterostachyum Nr -30.5 Africa PRE, US pyrularium Nr -29.4 S. Am. US robynsii Na Africa US snowdenii Na Africa US trichanthurn (2) Nar -28.4 S. Am. US, TEX trichoides (3) Nar -29.9 World NSW, US 27. Group “Depauperata” (x-?) cupressifolium Nr -27.6 Madag. US spergulifolium Na Madag. US 28. Group “Verrucosa” (x=9) brachyanthum Nr -28.3 U.S.A. TEX verrucosum Nr -25.6 U.S.A. TEX 29. Section Verruculosa (x = ?) frederici Nr -24.6 Africa US fulgens Na Africa US graciliccude Nr -29.6 Africa US hystrix Na Africa US ianthum Na Africa US prialturn Na Africa US pubiglume Nr -27.0 Africa US sublaetum Nr -25.6 Africa US Miscellaneous bartlettii Nr -28.3 C. Am. TEX hirtum (3) Nar -30.7 C. Am. US, TEX ovaliferum Na S. Am. TEX pantrichum Nr -30.4 Mexico US penicillatum Na S. Am. TEX spathellosum N S. Am. TEX subxerophilum Nar -25.8 Aust. NSW trigonum Na Asia TEX With the removal of Steinchisma (see previous section), the wholly American group ‘kLaxa” of Hitchcock and Chase (1910) seems to be a typical, tropical, non-Kranz taxon both anatomically and biochemically (by 813C ratios), except for a few C4 enzymes in Panicum laxum (Medina, Bifana, and Delgado, in litt.). Their proposal that P. laxum may be a C3 species derived from some C4 ancestor, because it grows in wet places and has senescent plastids in parenchyma sheath cells, is probably based upon incorrect assumptions. These are that C4 taxa all evolved in arid regions and might evolve back to C3 species in wet habitats, and MEMOIRS OF THE TORREY BOTANICAL CLUB 47 that unusual chloroplasts in parenchyma sheath cells may indicate degenerate kranz cells. Rather, the habitat and un¬ usual chloroplasts in parenchyma sheath cells of P. laxum are not unusual among non-Kranz grasses. The “Laxa” group is non-Kranz with smooth fertile lemmas and, therefore, is included in the sub¬ genus Sarmentosum (Table 8). It is proposed to revive Phanopyrum gymnocarpon Nash for that monotypic American species usually designated as Panic am gymnocarpon Ell., because it is morphologically distinctive and is non-Kranz. The Panicum subgenus Phanopyrum of Pilger (1940) and Hsu (1965), containing sections Gymnocarpa and Dura and groups “Megista” and “Obtusa,” is too heterogeneous for ac¬ ceptance (Tables 6 and 7). Group “Fasciculata” of Panicum was transferred to Brachiaria by Pilger ( 1940) and Hsu (1965). That transfer, based upon morphological characters, is sup¬ ported by this and other studies (Gutier¬ rez, Edwards, and Brown, 1976). Both “Fasciculata" and Brachiaria have, uniquely in the Paniceae, PEP-ck photo¬ synthesis and transversely rugose fertile lemmas. Whether P. texanum, P. fas- ciculatum, etc., which constitute “Fas- ciculata, should all be transferred to Brachiaria, as has been done, or, like P. deflexa, which now constitutes Pseudobrachiaria, become one or more new genera, is not indicated by this work. Old World agrostologists place the Asi¬ atic species P. ramosum L. in Brachiaria (Bor, 1960), whereas Hitchcock (1950) included it in “Fasciculata.” A compari¬ son of Asiatic B. ramosa (L.) Stapf, American P. fasciculatum Swartz, South African P. chusqueoides Hack., and South African B. ( Pseudobrachiaria ) de¬ flexa (Schum.) C. E. Hubb. ex Robyns demonstrates great similarity among them. Chippindall (1955) remarked about the last species (p. 378), “Some botanists treat the group to which B. deflexa belongs as species of Panicum. If the grass in question is retained as a species of Brachiaria , then Panicum chus¬ queoides should probably be referred to Brachiaria .” And on p. 326, about P. chusqueoides, “This species should pos¬ sibly be referred to Brachiaria, for it is hardly separable from the section of that genus to which B. deflexa belongs.” For the present, at least, all these P.S., PEP- ck species having usually transversely rugose fertile lemmas and more or less racemose inflorescences should be trans¬ ferred to Brachiaria. Henrard's( 1940) transfer of non-Kranz Panicum venezuelae to Brachiaria is not supported by leaf anatomy or surface character of the fertile lemma. The species often called Panicum pur- purascens Raddi in the United States, of group “Purpurascentia,” is clearly Brachiaria mutica Stapf., and P. reptans L. clearly belongs in the Brachiaria group as Urochloa reptans (L.) Stapf. or B. reptans (L.) Gard. and C. E. Hubb. Panicum paucispicatum Morong of Paraguay and Bolivia was transferred to Acroceras by Henrard ( 1940). However, Acroceras is a non-Kranz genus with nearly smooth fertile lemmas, whereas P. paucispicatum is Kranz and has rugose lemmas. The latter probably belongs in the Brachiaria group, possibly as a monotypic genus. Panicum maximum and other species. 48 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS placed in section Maxima by Hsu (1965) and others, present problems in relation¬ ship. Panicum maximum is Kranz P.S. and PEP-ck (Table 1), so should be placed in the Brachiaria group; P. bul- bosum and P. plenum are Kranz M.S., and doubtlessly NADP-me. They can best be included in a group of M.S. taxa that are exclusively American except for P. antidotale Retz., which is native to India. Panicum transvenulosum, being non-Kranz, should certainly not be as¬ sociated with P. maximum or P. bul- bosum. The other species included by Stapf (1920) in the group with rough lem¬ mas are P.S., but whether PEP-ck or NAD-me is not known. If PEP-ck, like P. maximum, they should also be trans¬ ferred to the Brachiaria group. It is likely that P. trichocladum and P. spongiosum, with smooth and polished fertile lemmas, are not PEP-ck species. The M.S. paniculate species Panicum bulbosum, P. plenum, and P. antidotale are associated as the group “Plena” al¬ though they may have had separate origins. Panicum plenum and P. bul¬ bosum may be conspecific. The other, all American, M.S. groups of Panicum (“ Agrostoidea,” “Tenera,” “Obtusa,” “Discrepantia,” “Tuerck- heimiana,” and at least two species of “Grandia;” Table 7) seem out of place among the non-Kranz and Kranz P.S. taxa of the genus. Anatomically they re¬ semble more closely the bulk of Kranz genera of Paniceae. It seems likely that they have evolved completely indepen¬ dently of P.S. Panicum. Possibly they are more closely allied to other M.S. Paniceae, or they may be more or less recent derivatives of non-Kranz Paniceae. In either case, they could be considered as distinct genera. Panicum discrepans Doell, for exam¬ ple, has Kranz cells with unusually thick walls around the small veins, but the inner and lateral walls of the Kranz cells around larger veins are very thick, as thick as the walls of mestome sheath cells in non-Kranz species. Much the same is true of P. petersonii. I propose that such anatomy indicates recent evolution of the Kranz syndrome and of the M.S. Kranz sheath from the mestome sheath. It is not proposed that the M.S. groups of Panicum be associated as an interre¬ lated assembly but rather as more or less unrelated taxa. Some may represent rather recent and independent evolutions of the M.S. subsyndrome. Certainly the Kranz M.S. species of the group “Gran¬ dia” appear to be products of such a re¬ cent evolution. It is tentatively proposed that “Grandia” is more closely related to the unusual genus Steinchisma than to non-Kranz Panicum. Of the three species examined from section Clavelligera, two are non-Kranz and one, Panicum deustum, is Kranz. Al¬ though it is possible to have two closely related species be Kranz and non-Kranz, it is not likely in this group. Therefore, I propose to remove the Kranz species, P. deustum, and leave the section a non- Kranz taxon. Its remaining species are most closely related to the two non- Kranz sections Monticola and Pectinata (Hsu, 1965). Section Sarmentosa becomes a non- Kranz taxon with the removal of Panicum antidotale . The placement of that species in M.S. “Plena” has been discussed above. MEMOIRS OF THE TORREY BOTANICAL CLUB 49 FIGURE 2. Photomicrograph of a partial midrib cross section showing M.S. anatomy with a parenchyma sheath present in Panicum petersonii. One bundle (center) and part of another (lower right) are shown. The mestome sheath cells (K, M.S.) contain chlorophyll , but over the xylem (Xy) they are very thick-walled ( M.S. ). The cells of the parenchyma sheath ( P.S.) are large and empty of chlorophyll , and the sheath is continu¬ ous over the sclerenchyma (Sc) between the two bundles. The phloem (Pli) of both bundles is visible. The lower bundle is closer to the surface of the midrib, which constitutes nearly all of the blade in this Cuban species. See text for discussion. ca.SOOX . 50 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS The group “Grandia” is unique be¬ cause it appears to contain both Kranz and non-Kranz species. Hitchcock ( 1915) stated that Panicum grande is mor¬ phologically close to P. grumosum, P. rivulare, and P. prionitis; that P. stag- natile is close to P. rivulare; and (1936) that P. petersonii is close to P. prionitis. Thus, the group seems to be composed of related species. On the other hand, four species are non-Kranz, whereas P. prionitis and P. petersonii have Kranz M.S. anatomy. The anatomy of the latter two species is unique and, in a sense, is intermediate between non-Kranz and Kranz. The M.S. Kranz cells are, for Kranz cells, very thick-walled and, in fact, part of the sheath may be composed of typical, very thick-walled, non-Kranz-like mestome sheath cells (Figure 2). This is especially common where the sheath surrounds the inner bundle when two are radially ar¬ ranged in the midrib, which essentially constitutes the blade in these species. Thus the Kranz sheath is obviously de¬ rived from the mestome sheath. Furthermore, the parenchyma sheath is still obvious, composed of not enlarged, thin-walled, apparently empty cells. The only other known examples of M.S. species having parenchyma sheaths are in Alloteropsis (Africa to Australia) and two species of Neurachne (Australia). They, too, are closely related to non-Kranz taxa, A. semialata var. eckloniana (Ellis, in press) and Thyridolepis. It is proposed that these three cases are examples of recently evolved Kranz syndrome. The mestome sheath cells are still small and the walls are excessively thick for Kranz cells. The parenchyma sheath, which is lost in all other M.S. species, persists. Rather than divide these apparently re¬ lated species between subgenus Sarmentosum (non-Kranz) and the M.S. groups (Kranz), it seems preferable, tem¬ porarily, to maintain “Grandia” separate from both (Table 8). It is interesting that this recent evolu¬ tion of the Kranz syndrome in Panicum yielded the M.S. anatomy characteristic of Kranz Paniceae in general, rather than the P.S. subtype of typical Panicum. It can be proposed that in the Paniceae gen¬ erally, evolution of the Kranz syndrome is almost always via the M.S. subtype. Perhaps only once has the Kranz syn¬ drome evolved via the P.S. subtype, to yield the P.S., NAD-me species of sub¬ genus Panicum (Tables 7 and 8). The P.S., PEP-ck species, though excluded from Panicum (the Brachiaria group), may have been derived from the same evolution of the P.S. subtype that yielded the subgenus Panicum. Certainly, tax¬ onomic treatments of the past indicate considerable similarity between sub¬ genus Panicum and the Brachiaria group (Brachiaria, Eriochloa, Urochloa, etc.), so a common ancestry seems likely (Fig¬ ure 1). Group “Hemitonia” Hitchcock, sometimes included in Panicum, has been transferred by Hsu (1965) to Hymenachne . Since P. hemitomon Schult. is non-Kranz, as is Hymenachne , this study, if anything, supports its trans¬ fer. Pohl and Lersten (1975), however, excluded P. hemitomon from Hymenachne because of its hollow inter¬ nodes and staminate lower florets. Thus, from Panicum as constituted by Hitchcock (1950), the following have MEMOIRS OF THE TORREY BOTANICAL CLUB 51 been transferred: Subgenus Paurochaetium to Setaria. Subgenus Dichanthelium to genus Dichanthelium. Group “Hemitoma” to Hymenachne? Group “Geminata” to Paspalidium. Group “ Purpurascentia” to Brachiaria. Group “Fasciculata” to the Brachiaria group. Group “Laxa” in part to genus Steinchisma. Group “Gymnocarpa” to genus Phanopyrum. Even with these transfers the genus remains a large and heterogeneous as¬ semblage of non-Kranz and Kranz, P.S. and M.S., NADP-me and NAD-me tax a. With these modifications among the sections and groups, the application of leaf anatomy at the subgeneric level de¬ serves consideration. It is evident that, with the Kranz P.S., PEP-ck species transferred out of Panicum to the Brachiaria group, four general types re¬ main (Table 8). There are two types of non-Kranz taxa (Hsu, 1965), those with smooth and those with rough fertile lem¬ mas, and two types of Kranz taxa, P.S. and M.S. The rough-lemma, C3 taxa can be included in Subgenus Megathyrsum Pilger, and the smooth lemma, C3 ones in subgenus Sarmentosum Hsu. The cor¬ responding Kranz taxa are subgenus Panicum with P.S. leaf anatomy, and a new informal assemblage of groups with M.S. leaf anatomy (Table 7). Subgenus Panicum is very homogene¬ ous (P.S., smooth and shining fertile lemmas) and the taxa included here cor¬ respond quite well with those included by Hsu (1965). The M.S. groups have little in common except that subtype of leaf anatomy. Be¬ cause the M.S. condition is typical of most Kranz Paniceae except the Brachiaria group and subgenus Panicum, it is possible that the M.S. groups would best be treated as distinct genera, perhaps of recent origins along with “Grandia.” The two non-Kranz subgenera are not homogeneous. Some groups are related, such as “Parvifolia,” “Parviglumia,” and “Stolonifera,” but others, such as “Megista,” section Depauperata, and “Verrucosa,” are individually unlike any others. It can be concluded that each subgenus includes present-day termini of a number of evolutionary lines, many of which have been distinct for a long time. Type of leaf anatomy is assumed to be the best available character for delimiting subgenera, and character of the fertile lemma surface seems to be equally good at the next lower level of classification. Utilization of these characters has not greatly modified the groups and sections as based upon morphological characters, but has grouped them at the subgeneric level. If leaf anatomy and correlated biochemistry are as significant in sys- tematics as is assumed here, it follows that the genus Panicum might be con¬ ceived as limited to the homogeneous subgenus Panicum. That may be achieved eventually, but should not be attempted until a very detailed acquain¬ tance with all the species of the genus has been acquired. Chromosome counts for species of Panicum are now numerous. It is evident that there are two basic chromosome numbers within the genus, 9 and 10. Of these, 9 is the more common. When available numbers were assigned to the species listed in Table 7, it became evi- 52 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS dent that most groups and sections are uniform for one or the other basic number. Furthermore, the whole sub¬ genus Panicum is characterized by the basic number 9, reflecting the general uniformity of that taxon. The three other subgenera each contain both x = 9 and x = 10 taxa, which parallels their mor¬ phological heterogeneity. TABLE 8. Supraspecific taxa o/Panicum, arranged according to types of leaf anatomy, photosynthesis , and fertile lemma surface. Non-Kranz, C3 Kranz, C4 Fertile lemmas rough Subgenus Megathyrsum Hsu P.S., NAD-me fertile lemmas smooth Subgenus Panicum section Clavelligera Stapf section Depauperata Pilger section Monticola Stapf section Pectinata Stapf group "Trichoidea” Hitchc. section Trinerves Stapf group "Verrucosa H. and C. section Verruculosa Stapf section Panicum group “ Dichotomiflora” H. and C. group “Diffusa” H. and C. section Repenlia Stapf section Dura Stapf group "Rudgeana” Hitchc. P.S., PEP-ck fertile lemmas rough Questionably "true” panicums Fertile lemmas smooth Subgenus Sarmentosum Hsu M.S., NADP-me Miscellaneous Assemblage group "Laxa H. and C. group “Parvifolia" H. and C. group " Parviglumia” H. and C. group "Stolonifera" H. and C. group "Megista" Hitchc. section Sarmentosa Pilger group "Haenkeana” Hitchc. group " Agrostoidea” H. and C. group "Obtusa” H. and C. group "Plena” W. V. Brown group "Tenera” H. and C. group "Discrepantia” W.V. Brown group "Tuerckheimiana” Hitchc. group "Grandia” Hitchc. (pars) . - group "Grandia” (pars) MEMOIRS OF THE TORREY BOTANICAL CLUB 53 There are a few transfers of species indicated by basic chromosome numbers. Both Pcinicum elephantipes of tropical America and P. glabrescens of Africa appear to have x = 10 but P.S. anatomy. They have been removed tentatively from subgenus Pcinicum. Panicum glutinosum (x = 10) has been removed from section Sarmentosa, which seems to have a basic number of 9. Section Monticola has one species reported as x = 9 and one reported as x = 10, so no generalization as to basic number is pos¬ sible now. Pcinicum maximum seems to be characterized by the unusual chromo¬ some number 2n = 32. It is interesting that P. trichocladum, which Stapf (1920) put in the same section with P. maximum, also appears to have 2n = 32. These two appear to be the only species of Panicum with a basic number other than 9 or 10. Neglecting apomictic species, which often have aneuploid numbers, there are species in other genera, such as in Pennisetum and such as Brachiaria ( Panicum ) reptans L., with n = 7. The apparent x = 8 of P. maximum and P. trichocladum may further relate these two species to the Brachiaria group of PEP-ck genera. The chromosome numbers of Panicum species have been determined by many investigators and for this analysis were extracted from the standard published lists of chromosome numbers, especially the annual “Index to plant chromosome numbers,” (Regnum Vegetabile, Vol¬ umes 90, 91, and earlier). THE SMALL TRIBES OF THE PANICOIDEAE In addition to the large tribes An- dropogoneae and Paniceae, there are up to nine small tribes of Panicoideae. The present study provides evidence for maintaining these taxa as distinct tribes (Pilger, 1954) rather than for incorporat¬ ing some of them in the Paniceae. They have been sampled in order to make this survey as complete as possible and are discussed as tribes. Among them are non-Kranz, Kranz M.S., and Kranz P.S. taxa, but each tribe is homogeneous for leaf anatomical type. Cyphochlaeneae. This includes two or three very small genera endemic to Madagascar and adjacent islands ( Pilger, 1954). They have greatly modified spikelets and are non-Kranz (Table 9). They doubtless represent end lines of a group that has evolved in isolatior for a long time. Lecomtelleae. This is a monotypic tribe of Madagascar. Lecomtella madagascarensis is non-Kranz and, like the species of the Cyphochlaeneae, has evolved in isolation. Isachneae. This is a considerably larger tribe than the two above, but like them is all non-Kranz. Coelachne , H etc rant hoecia , Limnopoa , and Sphaerocaryum are small and geographi¬ cally restricted genera. Isachne, on the other hand, is pantropical (Potztal, 1952) (Table 9). It differs from non-Kranz Paniceae by having two hardened, usu¬ ally fertile florets per spikelet, the lem¬ mas of which have thread-like microhairs on their surfaces (Hsu, 1965). However, numerous species of Isachne have sterile lower florets, and a few Paniceae, such as the Hawaiian Dissochondrus , have fer¬ tile ones. Thus, the difference between Isachne and Paniceae is not great. It is assumed by agrostologists that the 54 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS original grasses had spikelets of numer¬ ous florets, so that taxa having spikelets of one or two florets are somewhat ad¬ vanced. Therefore, it is likely that evolu¬ tion leading to the typical spikelet of the Paniceae (two florets, of which the lower does not have lemma and palea indurated and is sterile or staminate) probably passed through a stage having two fertile and specialized florets, as occurs in the Isachneae. It can be proposed that the Isachneae represent modem descendants of that two-fertile-floret, non-Kranz, pre-Paniceae stage of evolution. It has already been stated that Chase (191 1) saw similarities between Isachne and Dichanthelium . The remaining small tribes all have Kranz leaf anatomy. TABLE 9. Species of the small panicoid tribes examined , arranged by tribes and genera: anatomical and photosynthetic characters , provenances, and voucher herbaria. Syndrome Anatomy 813C Provenance Herbaria BOIVINELLEAE Cyphochlaena madagascariensis Nr 32.5 Madag. P, US LECOMTELLE AE Lecomtella madagascariensis Nr 26.5 Madag. P ISACHNEAE Coelachne africana Nr 27.2 Africa US 4 other spp. (Potztal, 1952) Heteranthoecia Na Old World isachnoides (Potztal, 1952) Isachne Na Africa albens Na India US confusa Na Asia US disperma Nr ■27.1 S. Am. TEX distichophylla Nr 25.6 S. Am. TEX kunthiana Na Asia US polygonoides Na C. Am. TEX puhescens Nr 26.0 C. Am. TEX pulchella Nr ■27.7 India TEX rigidifolia Nr 25.8 W. Ind. TEX saxicola Na Asia US scabrosa Na Asia US 23 more spp. (Potztal. 1952) Na MEMOIRS OF THE TORREY BOTANICAL CLUB 55 Table 9 continued. Syndrome Anatomy 813C Provenance Herbaria Limnopoa meeboldii (Potztal, 1952) Sphaerocaryum Na India malaccense (Potztal, 1952) Na Asia ANTHEPHOREAE Anthephora cri statu ka MS. Africa TEX hermaphrodita (2) kar M.S. -11. 1 America TEX pubescens kar M.S. -12.5 Africa TEX hochstetteri (Giinzel, 1912) ka undidatifolia (Giinzel, 1912) ka TRACH YE AE T tetchy s m uric a t a kr M.S. -11.6 India US MELINIDEAE Melinis minutiflora Rhynchelytrum kar P.S. -12.7 S. Am. TEX repens Tricholaena kar PS. -12.7 Africa TEX capensis ka P.S. Africa TEX monachne kar P.S. -11.9 Africa PRE, TEX teneriffae Neyraudia ka P.S. India TEX reynaudiana (Tateoka, 1956) ka P.S. ARTHROPOGONEAE Achlaena piptostachya Arthropogon ka M.S. Cuba TEX scaber (Tateoka, 1963b) ka P.S. ! US villostts ka M.S. -13.3 US xerachne (Tateoka, 1963b) ka P.S. ! US Reyna udia J'lliformis Snowdenia ka M.S. -11.6 W. Ind. TEX, US polystachya -13.5 US A R U N D INELLEAE Arundinella berteroniana kr M.S. -14.5 C. Am. TEX 56 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 9 continued. Syndrome Anatomy 813C Provenance Herbaria confinis Ka MS. Mexico TEX deppeana Kr -11.7 C. Am. TEX hirta (Tateoka, 1956, etc.) Race MS. Asia hispida Ka MS. India TEX leptochloa Ka MS. India TEX martinicensis Ka MS. W. lnd. TEX metzii Ka M.S. India TEX nepalensis (Tateoka, 1958) Kace P.S.! India palmeri Ka MS. Mexico TEX 11 other spp. (Tateoka, 1958) Danthoniopsis dinteri Ka MS. -12.5 Africa PRE Gilgiochloa indurata Ka M.S. -12.7 Africa PRE Loudetia kagerensis Ka MS. Africa TEX pedicellata ( deWet, 1960) Ka Africa rogerensis Kr -11.9 Africa US simplex Kar M.S. -11.4 Africa US, TEX sp. Ka M.S. Africa TEX Trichopteryx dregeana Kar M.S. -13.3 Africa PRE simplex Kar M.S. -11.4 Africa PRE stolziana Ka M.S. Africa TEX Tristachya avenacea Ka M.S. Mexico TEX biseriata Ka M.S. Africa TEX hispida Kar M.S. -1 1.4 Africa PRE GARNOTIEAE Garnotia acutigluma Kar M.S. -10.7 China US arundinacea Kar M.S. -11.5 India US stricta Kar M.S. - 9.5 India TEX triseta Ka M.S. China TEX 10 other spp. (Tateoka, 1958) TRACHYEAE Trachys muricata Kar M.S. -11.6 India US MEMOIRS OF THE TORREY BOTANICAL CLUB 57 Trachyeae. This possibly distinct tribe (Pilger, 1954; Potztal, 1957) is con¬ stituted by the single Indian species Trachys muricata. Hsu (1965) included the genus in the Paniceae. Smith and Brown (1973) recorded it as having a C4 813C ratio. Its leaf anatomy is M.S., which contributes nothing toclarifying its placement, however. Melinideae. This mostly African tribe of about four genera is unique among these small tribes of Panicoideae in having P.S. leaf anatomy (Table 9). Hsu (1965) maintained it as a distinct tribe and the leaf anatomy supports that deci¬ sion. The only other Panicoideae having P.S. leaf anatomy are the Brachiaria group of genera and the typical subgenus of Panicum. Spikelet comparison be¬ tween these taxa of Paniceae and the Melinideae suggests a relationship at the tribal level. Anthephoreae. This taxon compris¬ ing one genus and about 20 species can be considered as merely a highly specialized genus of Paniceae (Reeder, 1960; Steb- bins and Crampton, 1961 ; Hsu, 1965), as possibly crossable with Digitaria (Loxton, 1974), or as different enough from Paniceae to warrant status as a dis¬ tinct tribe (Pilger, 1940; Tateoka, 1957). No modern grass systematist places Anthephora anywhere except in the Panicoideae. Reeder (1960) reviewed the placement of Anthephora historically and compared one species, A. hermaphrodite! , to some Zoysieae and Paniceae. By all the usual characters (silica cells, bicellular hairs, chromosome size and basic number, and embryos) Anthephora is similar to Paniceae and all Kranz Panicoideae. The only character Reeder discussed that might help settle its placement was spikelet morphology, a subject of dis¬ agreement for 200 years. But he pre¬ sented no new evidence except a detailed comparison of internal “bur” structures in A. hermaphrodita with Cenchrus. Anthephora has leaf anatomy typical of most Kranz Panicoideae, the M.S. sub- type. However, the presence of “distinc¬ tive cells” in at least A. cristata is a re¬ cently discovered characteristic differen¬ tiating the genus (Johnson, 1964). Dis¬ tinctive cells (see later) have been re¬ ported in no grass taxa except a few of these small tribes of Panicoideae. Their presence plus the specialized spikelets and inflorescences suggest retention of the tribe Anthephoreae. Arthropogoneae. This is a tribe of four small genera, three American and one African (Table 9). Tateoka (1963b) and this study have demonstrated that all species are Kranz and that many possess distinctive cells. Tateoka reported the P.S. subtype of Kranz anatomy but I found the M.S. subtype in those same species. For uniformity of comparison with other Kranz taxa, the Ar- thopogoneae are here treated categori¬ cally as being M.S. Although the African genus Snowdenia is Kranz (Smith and Brown, 1973), its type of leaf anatomy was not determined. Its relationship to the American genera is somewhat ques¬ tionable (Tateoka, 1963b). Since it is assumed here that the pres¬ ence or absence of distinctive cells is a significant character in grass systematics, it is suggested that the genera of this group are distinct enough from all other taxa except Anthephoreae, Arundinel- 58 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS leae, and Gamotieae to justify mainte¬ nance of the tribe Arthropogoneae. Arundinelleae. This tribe of about six genera is centered in southern Africa except for the pantropical genus Arundinella. Hsu ( 1965) treated Arundinella as probably distinct from the Paniceae. Tateoka (1958) supported the concept of the tribe Arundinelleae and related it to the Gamotieae. The genera of Arundinelleae are Kranz M.S. (Con- ert, 1957; Metcalfe, 1960) (Table 9), al¬ though Tateoka (1958) described them as P.S. Tateoka (1958) and Hsu (1965) placed the Arundinelleae in the Panicoideae, but Pilger (1954) placed the tribe in the Fes- tucoideae which, by most modem con¬ cepts, would be a very unnatural associa¬ tion. According to such modem criteria as silica cell, bicellular hair, and embryo characters, cytology, and leaf anatomy, the Arundinelleae belong in the Panicoideae. Spikelet structure indicates a relationship to the Paniceae or Dantho- nieae. Distinctive cells have been reported in numerous species of Arundinella (Tateoka, 1956a and b, 1958; Brown, 1958; Crookston and Moss, 1973) and in Loudetia and Trichopteryx. If presence of distinctive cells indicates phylogenetic relationship, as Tateoka (1958) and I assume, then the Anthephoreae, Ar¬ thropogoneae, Arundinelleae, and Gar- notieae are set off from all other tribes as a related group, possibly a single tribe. Spikelets of Arundinelleae have sim¬ ilarities to some of the two-floreted Danthonieae of South Africa, such as some species of Danthonia and all species of Pentameris and Pen- taschistis. De Wet (1954) stated that, "These . . . genera [Tristachya and Loudetia] and also the Danthonia species group including D. forskalii are closely related to the tribe Arundinel¬ leae. ” Furthermore, silica cells of some Danthonieae and bicellular hairs of most are similar to those of Arundinelleae and, in fact, all Panicoideae. Chromosome numbers within Arundinella itself and re¬ lated genera are now known to show a "lack of uniformity” (Li, Lubke, and Phipps, 1966) (n = 6 or 12, 7, 8, 9, 10). The Panicoideae, aside from apomictic species, which are common (Brown and Emery, 1958), are characterized by the basic numbers 5 or 10, and 9. In the Danthonieae, however, basic numbers of 6, 7, and 9 have been reported (de Wet, 1954; Brock and Brown, 1961). Thus the variable basic numbers of the Arundinel¬ leae are matched by similar variability in the Danthonieae. Leaf anatomy favors relationship to the Panicoideae. In the latter subfamily the Kranz species are mostly M.S. also (Table 9). The Kranz Danthonieae, Asthenatherum and Alloeochaete of South Africa (deWet, 1954) and Pheidochloa of Australia, have P.S. leaf anatomy. Therefore, any relationship of Arundinelleae to Danthonieae should not be to the known Kranz genera of Danthonieae. For the present, a position inter¬ mediate between the Danthonieae and the Paniceae seems appropriate. Garnotieae. This comprises one genus of about 30 species from southeast¬ ern Asia and southeastward (Tateoka, 1958; Gould, 1972). Pilger (1954) assigned Garnotia to a MEMOIRS OF THE TORREY BOTANICAL CLUB 59 monogeneric subtribe of the Eragrosteae. Tateoka ( 1 958) placed it as a monogeneric tribe in the Panicoideae on anatomical and epidermal leaf characters, and Gould (1972) agreed with that placement. It has M.S. leaf anatomy, unknown in the Erag- rostoideae but typical of the Panicoideae, and bicellular hairs quite unlike those of the Eragrostoideae. Tateoka and Gould considered it to be perhaps distantly re¬ lated to the Arundinelleae. Like the latter and some other small Kranz panicoid tribes, some species of Garnotia have distinctive cells (Tateoka, 1958). There¬ fore, inclusion of Garnotia in the Panicoideae seems adequately justified. Examination of transverse and lon¬ gitudinal views of distinctive cells and rows of such cells leads to the interpreta¬ tion that the longitudinal rows are rem¬ nants of Kranz sheaths of the small bundles which have no vascular tissue, as indicated by Tateoka (1958). Crookston and Moss (1973) observed in part that the (evident) vascular bundles of such a leaf are as far apart as in most non-Kranz species. If the rows of distinctive cells are vascular bundle sheath remnants, then they should be closely spaced, as they are, like the small bundles of typical Kranz leaves ( Hattersley and Watson, in press). Furthermore, lateral bundles do interconnect the true bundles and rows of distinctive cells, just as though the latter were small bundles. In species of Loudetia and Trichopteryx there are mul¬ ticellular strands of distinctive cells in¬ termediate in appearance between typical Kranz sheaths and single rows of distinc¬ tive cells, as also observed in Arundinella and Garnotia by Tateoka (1958). In Kranz species, ribulose diphosphate carboxylase (RuDP-Case) is mostly re¬ stricted to Kranz cells. That distinctive cells are indeed Kranz cells has been further indicated recently (Hattersley, et al., in press). Leaf sections were treated with antiserum to RuDP-Case carrying a fluorescent dye to reveal the sites of RuDP-Case in the leaf. The chloroplasts of the distinctive cells fluoresced as bril¬ liantly as did those of the Kranz sheath cells in the species Arundinella ne- pa lens is. It has been established, therefore, from studies of various species, that distinctive cells are quite certainly Kranz cells. They are similar for large agranal chloroplasts, storage of starch, thickness of walls with an electron-opaque band between such cells (Crookston and Moss, 1973), and now for presence of RuDP-Case. It is always possible to read evolution¬ ary change in either direction. Therefore, rows of single or multicellular distinctive cells may be stages in the evolution of the intercalary, closely-spaced, small bun¬ dles typical of Kranz grasses. Certainly, intercalary bundles have always evolved in grasses along with Kranz anatomy, and such closely-spaced bundles with Kranz sheaths do occur in some species of most or all genera reported to have distinctive cells. On the other hand, if Kranz cells not associated with vascular tissues (distinc¬ tive cells) work well enough in C4 photo¬ synthesis, perhaps rows of distinctive cells are developmental^ modified inter¬ calary bundles (degenerate bundles) rather than formative stages. This seems most likely and I propose it as a working hypothesis, although it is difficult to ac¬ count for such occurrence in only some 60 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS species of most genera of only these four small tribes. Because distinctive cells have been ob¬ served in no other Kranz genera of grass¬ es, it is assumed that this is a unique qualitative characteristic sufficient to in¬ dicate phylogenetic relationship among the small Kranz panicoid tribes Arun- dinelleae, Arthropogoneae, Gamotieae, and Anthephoreae, as stated in part by Tateoka (1958, 1963b). Thisjustifies their maintenance as four distinct but related tribes or as one inclusive tribe. Tateoka (1958, 1963b) concluded that the numerous species he examined of Arundinelleae, Garnotieae, and Ar¬ thropogoneae have a mestome sheath surrounded by a Kranz parenchyma sheath, P.S. leaf anatomy. After careful examination and reexamination of numerous species of these tribes against a background of experience with hundreds of Kranz grass species, I am certain that these are M.S. taxa. I cannot explain this difference of opinion over something so simple. At least they are M.S. according to my criterion for recognizing that sub- type, which is that in cross sections of larger veins, Kranz sheath cells are in contact tangentially with the large metaxylem vessels. The non-Kranz tribes Cyphoch- laeneae, Lecomtelleae, and Isachneae can be related to the non-Kranz genera of Paniceae, and to the non-Kranz subgen¬ era of Panicum. It is likely that the Cyphochlaeneae and Lecomtelleae have evolved certain spikelet specializations while the Isachneae have maintained the pre-panicoid condition (two fertile florets). Certainly these non-Kranz tribes have less specialized leaf anatomy and photosynthesis than do the Kranz tribes. Of the six Kranz tribes, the Melinideae are unusual in having P.S. leaf anatomy. They could be related by leaf anatomy to Eragrostoideae, P.S. Panicum, P.S. Paniceae, Stipagrostis of the Aristideae, or Kranz Danthonieae. Of these, the Eragrostoideae can be eliminated espe¬ cially because of their club-shaped bicel- lular hair cells. The P.S. Paniceae (the Brachiaria group) and P.S. Panicum (the typical panicums) seem to be recent ad¬ vanced types quite unlike the Melinideae. Stipagrostis also is a specialized type quite distinct from Melinideae. There¬ fore, the most likely relationship of the latter is to the Danthonieae or Panicoideae. If M.S. leaf anatomy does indicate supertribal relationship, the Arundinel¬ leae, Arthropogoneae, Anthephoreae, and Gamotieae seem closest to the M.S. Paniceae and Andropogoneae as, perhaps, a third offshoot from some common ancestor. The presence of dis¬ tinctive cells, however, does help to set them off from all other tribes of Gramineae. THE ANDROPOGONEAE Previous studies of leaf anatomy and photosynthesis have, without exception, reported species of the Andropogoneae to be Kranz (Table 10; 60 genera and 181 species), M.S. (Brown, 1975), and NADP-me (Table 1). This uniformity in¬ dicates that no other subtypes should be expected, except possibly in Micro- stegium. The latter, a small genus occur¬ ring from southern Asia eastward and to South Africa, is characterized by growing MEMOIRS OF THE TORREY BOTANICAL CLUB 61 in, and possibly requiring, dense shade. It has been well established that kranz species are, with few exceptions, re¬ stricted to bright light. Therefore, species of otherwise Kranz taxa that seem to re¬ quire low light intensity might be ex¬ pected to have non-Kranz leaf anatomy and/or biochemistry. If so, they would be examples of reverse evolution, from Kranz to non-Kranz. Taxa examined to check this possibility included four species of Microsteigum (Andropo- goneae), six species of Setaria subgenus Ptychophyllum (Paniceae), and some TABLE 10. Genera of Andropogoneae examined for Kranz characters by various investigators, arranged alphabetically . All species examined {numbers per genus as indicated) are Kranz. Among them, all those characterized as to anatomical and/or photosynthetic subtypes are M.S. and NADP-me. Amphilophis 3 Lasiurus 2 Andropogon 22 Manisuris 3 A pin da 1 Microstegium 4 Arthraxon 4 Miscanthus 3 Bothriochloa 8 Monocymbium 1 Chasmopodium 1 Miscanthidium 1 Chrysopogon 6 Pogonatherum 1 Coelorhachis 1 Phacelurus 1 Cymbopogon 6 Pseudo pogonatherum 1 Dichanthium 7 Rattraya 1 Diectomis 1 Rap his 1 Dimeria 1 Rhytachne T Eccoilopus 1 Rottboellia T Ely on urns 4 S a cchar ton 5 Eremochloa 2 Schizachyrium 4 Eremopogon i Sehima 1 Erianthus 5 Sorghastrum 1 Eriochrysis 1 Sorghum 1 1 Eulalia 5 Spodiopogon 1 Eulaliopus 1 The me da 6 Germainia 1 Trachypogon 2 Hackelochloa 1 U rely t rum T Hemarthria 4 Vetiveria 5 Heteropogon 1 Vossia 2 Hyparrhenia 6 Chionachne i Hypogynium 1 Coix i Imperata 3 Euchlaena Ischaemum 10 Poly toe a i tseilema 1 Tripsacum i Jardinea 2 Zea i Totals: 60 genera; 181 species. 62 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS species of Muhlenbergia (Eragro- stoideae). The four species of Microstegium and all species of Ptychophyllum have Kranz M.S. leaf anatomy, and M. vimineum has a 13C/12C ratio of - 13.8 and is N ADP-me (Gutierrez and Edwards, unpublished) (Table 11). It is true that the leaves of these species are thin for Kranz leaves. There are also some species of typi¬ cally xerophytic Muhlenbergia that usu¬ ally grow in the shade of moist woods or thickets and are found as far north as southern Canada (Hitchcock, 1950). These species, like all others of the genus, have Kranz leaf anatomy and/or 813C ratios (Table 11). In the northern extremes of their ranges they grow under conditions of low light intensity, low temperature, and high soil moisture, quite unlike those usually considered es¬ sential for, or characteristic of, Kranz species. TABLE 11. Some shade-tolerant species of Microstegium (Andropogoneae), Setaria (Paniceae), and Muhlenbergia (Sporoboleae): anatomical and photosynthetic characters, prove¬ nances, and voucher herbaria. Synd. 813C Anat. Prov. Herb. Microstegium ciliaturn Ka MS. India TEX glabra turn Ka MS. Fiji TEX nudum Ka MS. India TEX vimineum Kaer -13.8 MS. U.S.A. (intro.) TEX Setaria, subgenus Ptychophyllum barbata Kar -10.8 MS. S. Am. US chevalieri Ka MS. Africa TEX membranifolia Kar -12.0 M.S. S. Am. US palmifolia Ka M.S. Asia TEX paniculifera (3) Ka M.S. S. Am. TEX poiretiana Kar -11.2 M.S. S. Am. US Muhlenbergia frondosa (Pohl) Ka P.S. U.S.A. TEX glabriflora (Pohl) Ka PS. U.S.A. TEX mexicana Kar -13.4 P.S. U.S.A. TEX schreberi Kar -15.0 P.S. U.S.A. TEX sobolifera (Holm) Ka P.S. U.S.A. TEX sylvatica Kar -13.2 P.S. U.S.A. TEX tenuiflora Ka P.S. U.S.A. TEX MEMOIRS OF THE TORREY BOTANICAE CLUB 63 The only Kranz dicotyledonous species known to require dense shade occur in Chamaesyce (Euphorbiaceae) (Pearcy and Troughton, 1974). In Hawaii there are a few species of this genus that are restricted to the dense shade of rain forests. Nevertheless, they are definitely C4 according to the 13C/12C ratios re¬ ported. They are also rare examples of woody Kranz species. There are also species of the grass genus Brachiaria, such as B. miliiformis, B. re mot a, and B. setigera of India and Ceylon (Bor, 1960), that at least some¬ times grow in rather dense shade. These and Muhlenbergia (M. schreberi , Table 1) are or should be PEP-ck, whereas Microstegium , Setaria (Table 1), and Chamaesyce (Table 2) are or should be NADP-me. Thus, reversion of Kranz taxa to shade-tolerance or shade- requirement is not correlated with tax¬ onomy or photosynthetic biochemistry. All known shade-requiring species of otherwise Kranz taxa are themselves Kranz. There is no evidence that reverse evolution (Kranz to non-Kranz) has ever occurred, although it has been invoked in the attempt to reconcile Kranz/- non-Kranz patterns with taxonomic and phylogenetic schemes (Carolin, Jacobs, and Vesk, 1975). These results indicate that when Kranz species adapt to shade they conserve the Kranz anatomy, C4 photosynthesis, and perhaps the biochemical subtype of their high-light-requiring ancestors. Neverthe¬ less, it seems likely that in some aspects their photosynthesis and/or photorespira¬ tion might differ from those of related Kranz species that require full sunlight. The complete uniformity of the An- dropogoneae for the Kranz syndrome can be interpreted as indicating its origin rather recently from some Kranz panicoid grass. A relatively recent origin of the tribe in tropical Africa and/or Asia has already been proposed (Hartley, 1958a; Whyte, 1973). It is possible that those tribes of the Panicoideae (excluding the Paniceae and Melinideae at least) that have Kranz M.S. leaf anatomy, a basic chromosome number of 10, and delicate, often awned, fertile lemmas might have had a common origin. This would relate the Andropogoneae to the Arudinelleae, Arthropogoneae, Anthephoreae, and Gamotieae. THE DANTHONIEAE The tribe Danthonieae may well rep¬ resent a central group in the evolution of the Gramineae. As more and more is learned about the leaf and other charac¬ ters now assumed to be most significant in the systematics of the family, increas¬ ing numbers of tribes and genera seem to show possible relationships to the Danthonieae. And the Danthonieae themselves show considerable variation in such basic characters as chromosome number, spikelet morphology, floret number, silica cell form, and leaf anatomy. The number of generic segre¬ gates from southern African and Au¬ stralian Danthonia during the past dec¬ ades has been large. Previous studies by de Wet (1954, 1956) demonstrated this variability and pointed out that two gen¬ era segregated from non-Kranz Danthonia, Asthenatherum and AUoeochaete , by Nevski (1934) and 64 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Hubbard (1940) respectively, are Kranz. ing examination of leaf anatomy and/or The tribe deserves extensive and inten- 13C/12C ratios, and the literature (Table sive study, and a survey of all available 12). genera was therefore undertaken, includ- TABLE 12. Species of Danthonieae examined for Kranz characters by various investigators, arranged by genera: anatomical and photosynthetic characters, provenances, and voucher herbaria. Data from this study unless otherwise attri¬ buted. Synd. Anat. S13C Prov. Herb. Afrachneria ampla (de Wet. 1956) Na -29.3 Africa US a urea (de Wet, 1956) Na Africa PRE capensis (de Wet. 1956) Na -24.5 Africa US capillaris (de Wet. 1956) Na Africa PRE ecklonii (de Wet, 1956) Na Africa PRE microphylla (de Wet, 1956) Na Africa PRE Alloeochaete namuliensis (de Wet, 1956) ka Africa PRE Amphibromus neesii Na Aust. US quadridentulus Na S. Am. US Amphipogon caricinus (2) Na -25.9 Aust. NSW, US turbinatus Na -24.5 Aust. US Anisopogon avenaceus Na -27.6 Aust. NSW Asthenatherum forskalii (de Wet, 1954) Ka Africa PRE glaucum (de Wet, 1954) Ka P.S. -12.7 Africa PRE mossamedensis (2) (de Wet, 1954) Ka P.S. -12.6 Africa PRE, TEX pumila (de Wet, 1954) Na? Africa PRE Chaetobromus dregeanus (de Wet, 1956) Na Africa PRE involucratus (de Wet, 1956) Na Africa PRE schraderi (de Wet, 1956) Na Africa PRE Chionochloa australis (de Wet, 1956) Na N. Z. PRE conspicua (C. J. V., 1973) Nae Aust. NSW crassiuscula (de Wet, 1956) Na N. Z. PRE oreophila (de Wet, 1956) Na Aust. PRE Danthonia californica Nar -27.4 U.S.A. TEX disticha Nar -25.4 U.S.A. TEX intermedia Nr -25.6 U.S.A. TEX monticola (C.J.V., 1973) Nae Aust. NSW MEMOIRS OF THE TORREY BOTANICAL CLUB 65 Table 12 continued. Synd. Anat. 813C Prov. Herb. pallida (C.J.V.. 1973) Nae Aust. NSW purpurea (2) (de Wet, 1954) Nar -25.9 Africa PRE. TEX purpurascens' Na Aust. NSW semiannularis (2) (de Wet, 1954) Nar -27.3 Africa PRE, TEX s pic at a (2) (de Wet, 1954) Nar -26.4 U.S.A. TEX, PRE vickeryi 2 Na Aust. NSW 37 more spp. (de Wet, 1954) Na Africa US Diplopogon set ace us (2) Nar -24.8 Aust. NSW. US Monachather paradoxus (2) Na Aust. NSW. TEX Monostachya oreoboloides Na N . Guin. NSW Notochloe sp. (Decker, 1964) Na Aust. Pentamaris dregeana (de Wet. 1956) Na Africa PRE longiglurnis (de Wet, 1956) Na Africa PRE macrocalycina (2) (de Wet, 1956) Nar -24.9 Africa PRE, US obtusifolia (de Wet, 1956) Na Africa PRE thuarii (de Wet, 1956) Na Africa PRE Pentaschistis macrantha Nr -25.5 Africa US 3 1 more spp. (de Wet, 1956) Na Africa PRE Pheidochloa gracilis Kar PS. -12.5 Aust . NSW Plagiochloa uniolae (de Wet, I960) Na Africa Poagrostis pus ilia (2) (de Wet, 1956) Nar -26.8 Africa PRE. US Prionathium ecklonii (de Wet, 1956) Na Africa PRE Schismus aristulatus (de Wet. 1956) Na Africa PRE bar bat us (2) (de Wet, 1956) Nar -22.7 Africa PRE, US bar bat us (2) (C.J.V., 1973) Nae Aust. NSW inermis (de Wet. 1956) Na Africa PRE Sieglingia decumbens (Tateoka, 1956) Na 'Danthonia purpurascens J. Vickery is now Notodanthonia teruiior (Steud.) S. T Blake (Blake. 1972) 2 Dunthonia vickeryi Hubb. is now Plinthanthesis nnillei Steud. (Blake. 1972). Pilger (1954) included Amphipogon and Diplopogon in the Aristideae. Most treatments place these Australian genera in the Danthonieae along with Kranz 66 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Pheidochloa. If the Aristideae are very close to some Danthonieae, then tribal assignment becomes a matter of arbitrary definition. For the present it seems best to restrict the Aristideae to species with one floret per spikelet. It is evident that most genera of Danthonieae are non-Kranz. The Kranz genera are Alloeochaete and As- thenatherum of southern Africa and Pheidochloa of Australia. No species of Alloeochaete were examined, but de Wet (1956) stated that the genus has panicoid (Kranz) leaf anatomy. Asthenatherum and Pheidochloa (and possibly Alloeochaete ) are P.S. In that they resemble Eragrostoideae, Stip- agrostis of the Aristideae, Eriachne, Melinideae, and some Paniceae. Of these, the Eragrostoideae are least like them on the basis of silica cells and bicel- lular hairs. The P.S. Paniceae seem more likely to be recent derivatives of non- Kranz Paniceae than of Kranz Danth¬ onieae. In most characters the Aristideae are similar to the Danthonieae and might be considered as specialized, single- floreted Danthonieae, just as Pheidochloa is like a two-floreted Aristida. Eriachne also is much like a two-floreted Aristida, but differs from all tribes in some characters (see later). It is also typical of all these P.S. taxa, except the Eragrostoideae, to have the walls of the mestome sheath cells, at least over the xylem, much thinner than is typ¬ ical in non-Kranz tribes. Another characteristic shared by these P.S. genera is Kranz cells that, in para- dermal view, are longer than wide, somewhat like those of the M.S. subtype (Brown, 1974). In contrast, Kranzcellsof Eragrostoideae and subgenus Panicum are short and radially wide (Brown, 1974). Such elongate P.S. Kranz cells are found in Melinideae, Paniceae ex¬ cept subgenus Panicum, Stipagrostis, Eriachne, Pheidochloa , and As¬ thenatherum. Actually, these genera have Kranz cells statistically longer than those in the Eragrostoideae and sub¬ genus Panicum, and statistically some¬ what shorter than Kranz cells of M.S. genera. As indicated in Figure 3, the Aristideae may have evolved from ancient Danth¬ onieae, probably in Africa, where the non-Kranz genus of Aristideae, Sartidia, and most of the more abundant Stipagrostis occur. The Danthonieae may represent the ancient grasses which first evolved the mesocotyl, and the very ancient transition to the subfamilies Arundinoideae, Panicoideae, and Erag¬ rostoideae (Figure 4). THE ARISTIDEAE It has been known since about 1900 (Holm, 1901) that A ristida is all Kranz but has two sorts of leaf anatomy. Some species have one Kranz sheath, the parenchyma sheath, whereas others have two sheaths that are both considered to be Kranz sheaths. More recently, the presence of two sheaths in Aristida has been confirmed at both the light microscope level (Henrard, 1929; Lommasson, 1957; Brown, 1958; Caceres, 1961 ; Bourreil, 1962) and that of the electron microscope (Johnson, 1964; Johnson and Brown, 1973; Carolin, Jacobs, and Vesk, 1973). The latter MEMOIRS OF THE TORREY BOTANICAL CLUB 67 TABLE 13. Species of Aristideae examined for Kranz characters by various investigators , arranged by sections and genera: anatom¬ ical and photosynthetic characters, provenances, and voucher her- baria. Data from this study unless other wise attributed . 813C Anat. Prov. Herb. A R 1 STI I DA Section Adscensiones longispica — 12.2 D.S. U.S.A. TEX oligantha -12.0 D.S. USA. TEX Section Arthratherum californica -12.7 D.S. U.S.A. TEX browniana D.S. Aust. NSW desmantha -12.6 D.S. U.S.A. TEX meridionalis -12.6 D.S. Africa PRE Section Chaetaria a r mat a DA. Aust. NSW canescens — 12.2 D.S. Africa PRE ramosa D.S. Aust. NSW Section Dichotoma basiramea -12.0 D.S. U.S.A. TEX dichotoma -12.6 D.S. U.S.A. TEX Section Divaricata divaricata -12.0 D.S. U.S.A. TEX pans a -14.0 D.S. U.S.A. TEX Section Pseudoarthratheum congesta -12.1 D.S. Africa PRE Section Pseudochaetaria hordeacea (2) -12.8 D.S. Africa PRE Section Purpurea fendleriana -12.4 D.S. U.S.A. TEX tenuispica -12.5 D.S. U.S.A. TEX glauca -13.4 D.S. U.S.A. TEX purpurea -13.8 D.S. U.S.A. TEX wrightii -13.0 D.S. U.S.A. TEX Section Schizachne parvula -12.8 D.S. Africa PRE Section Streptachne orcuttiana -12.7 D.S. U.S.A. TEX schiedeana -13.2 D.S. C. Am. TEX ternipes (2) -12.7 D.S. U.S.A. TEX utilis D.S. Aust. NSW 72 more spp. by various authors acutifolia STI PAGROSTIS P.S. (Holm, 1901; Bourreil, 1962) 68 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 13 continued. 813C Anat. Prov. Herb. amabilis -13.3 P.S. (deWinter, 1965) anornala -12.6 P.S. (deWinter, 1965) brachyathera P.S. (Holm, 1901; Bourreil, 1962) brevifolia P.S. (deWinter, 1965) ciliatum P.S. (Holm, 1901; de Winter, 1965 damarensis P.S. (deWinter, 1965) dinteri P.S. (deWinter, 1965) dregeanum P.S. (deWinter, 1965) fastigiata P.S. (deWinter, 1965) foexiana P.S. (Bourreil, 1962) garubensis P.S. (deWinter, 1965) geminifolia -12.0 P.S. (deWinter, 1965) gonatostachya P.S. (deWinter, 1965) hermannii -14.1 P.S. (deWinter, 1965) hirtigluma P.S. (deWinter, 1965) hochstetteriana P.S. (deWinter, 1965) lanipes P.S. (deWinter, 1965) lutescens P.S. (deWinter. 1965) namaquensis P.S. (deWinter, 1965) namibensis P.S. (deWinter, 1965) obtusa P.S. (deWinter, 1965) papposa P.S. (deWinter, 1965) pennata P.S. (Holm, 1901) plumosa P.S. (Holm, 1901, Bourreil. 1962) proximo P.S. (deWinter, 1965) pungens P.S. (Holm, 1901; Bourreil, 1962) raddiana P.S. (Bourreil, 1962) ramulosa P.S. (deWinter, 1965) sabulicola P.S. (deWinter, 1965) sahelica P.S. (Bourreil, 1962) schaeferi P.S. (deWinter, 1965) subacaidis P.S. (deWinter, 1965) uniplumis -12.1 P.S. (deWinter, 1965) zeyheri P.S. (deWinter, 1965) S A RT 1 D I A angolensis (2) -23.9 -26.6 Nar (deWinter, 1965) jacunda (2) -21.5 -24.4 Nar (deWinter, 1965) vanderijstii (2) -25.3 -26.5 Nar (deWinter, 1965) sp. -26.4 Nr MEMOIRS OF THE TORREY BOTANICAL CLUB 69 studies have revealed that the cell walls of the inner sheath are very thick for Kranz cells, and that the chloroplasts are nearly agranal and lie in the centrifugal regions of the cells. There are large pits in the thick walls between these cells and be¬ tween them and the cells of the outer sheath. The cell walls of the outer sheath are quite thin, and the chloroplasts are granal and lie in the centripetal regions of the cells. Recently Hattersley, et al. (in press) treated leaf sections of three species of Aristida with Ru DP-Case antiserum car¬ rying a fluorescent dye. Such a complex combines with RuDP-Case and reveals its location by fluorescence. The chloro¬ plasts in both sheaths of Aristida were thus shown to contain RuDP-Case, thereby indicating that both sheaths con¬ sist of Kranz or at least Kranz-like cells. De Winter (1965) demonstrated from a study of leaf anatomy that there are really three genera involved. Aristida has two Kranz sheaths; Stipagrostis has one Kranz sheath, the parenchyma sheath, as well as a mestome sheath of quite thick- walled cells; and Sartidia is non-Kranz with typical mestome and parenchyma sheaths. These three genera constitute the tribe Aristideae. The 13C/12C ratios determined in this study confirm that Aristida and Stipagrostis are C4 and that Sartidia is C3 (Table 13), as predicted from leaf anatomy. Because Stipagrostis is P.S., it is predicted to be N AD-me. And because in Aristida the mestome sheath consists of large Kranz cells with nearly agranal, centrifugal chloroplasts, whereas the presumed Kranz cells of its parenchyma sheath are small, it is predicted to be NADP-me. Gutierrez, et al. (unpubl.) have determined that one species, A. purpurea , is indeed of that subtype. Sartidia, with three or four species, grows in mesic, subtropical, southern Af¬ rica. Stipagrostis occurs in very arid southern and northern Africa and east¬ ward to Afghanistan. Aristida is reported from arid to mesic, tropical to warm temperate regions around the world. FIGURE 3. Evolutionary scheme of the Aristideae . Stipagrostis (extreme xerophytes) K. P S. i i Possibly the Sartidia (mesophytes) Danthonieae ^ non-Kranz Aristida (xerophytes often) K. modified M S. 70 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS I propose that Sartidia represents the original non-kranz Aristideae of mesic origin in southern Africa. (Figure 3). Be¬ cause of the significant anatomical and biochemical differences between Stipagrostis and Aristida, it seems likely that the Kranz syndrome originated twice among C3 Aristideae in southern Africa, once to produce the P.S. type (Stipagrostis) and once to produce the modified M.S., the D.S., type (Aristida). In most M.S. taxa the parenchyma sheath has been lost, but in Aristida it too became a Kranz sheath, although appar¬ ently one of minor functional signifi¬ cance. TABLE 14. Comparison of various grass taxa by significant morphological, anatom¬ ical, and cytological characters . Character Eragrostoideae Paniceae Aristideae Danthonieae Eriachne embryos1 P + PF P - PP P - FF and P-PF P-PF 9 lodicules truncate truncate elongate truncate truncate to elongate leaf anatomy P.S. N, P.S., M.S. N. P.S., D.S. N, P.S. P.S. K cells 1/w2 wide wide to long' long4 wide to long- long4 K plastids3 Cp, Cf Cp, Cf Cf + Cp 7 bicell, hairs club linear linear linear linear on leaves 7.24 2.7 3.2 3.4 3.2 (estimate) on lodicules absent absent absent present 7 silica cells kidney to double ax dumbbell dumbbell, to circular dumbbell, various transversely saddle hila basal, punctate basal, punctate linear short to Vi grain 7 chromosome base no. 9, 10 9, 10 1 1 6(12), 7 9 1 Symbolism of Reeder (1957) — 1st: P = mesocotyl present; 2nd: + = epiblast present; 3rd: P = scutellum separated from coleorhiza, F = these not separated; 4th: F = first seedling leaf narrow and not overlapping, P = first seedling leaf wide and overlapping. 2 Kranz cells length/width ratios in longitudinal view (Brown, 1974). 3 Kranz cell plastids: Cp = located centripetally, Cf = located centrifugally (Brown, 1960). 4 Numbers from Tateoka, et al. ( 1959): high numbers, apical cell is short and wide; low numbers, apical cell is long and narrow. The Aristideae have no evident rela¬ tionship to any of the Eragrostoideae (Table 14). They are closer to the Paniceae and/or the Danthonieae. Eriachne and Pheidochloa, possibly be¬ longing in the Danthonieae, are very much like a hypothetical two-floreted, single-awned Aristida. Eriachne, Pheidochloa , Asthenatherum , Al- loeochaete , and Stipagrostis are entirely P.S. with large glumes and similar bicellu- lar hairs and silica cells (Caceres, 1961; de Winter, 1965), and they, along with non-kranz Sartidia (de Winter, 1965), MEMOIRS OF THE TORREY BOTANICAL CLUB 71 have rather thin-walled mestome sheath cells. Furthermore, in Aristida (Lommasson, 1957; this study), as in Eriachne, the sheath cells are very, al¬ most uniquely, long and are parallel to the bundle. Overall, the Aristideae seem re¬ lated to the Danthonieae. ERIACHNE This genus of about 35 mostly Au¬ stralian species has been variously placed in different systems proposed for the Gramineae, or it has remained unplaced because of its peculiarities. Tateoka (1961b) examined the leaf anatomy and epidermal characters of most species and concluded only that, “the affinity of Eriachne ought to be sought in some panicoid or danthonioid group.” He did demonstrate that Eriachne is a genus of Kranz species that have thread-like bicel- lular hairs. The Panicoideae, Danth¬ onieae, and Aristideae have species pos¬ sessing these characters. That the species of Eriachne are P.S., as reported by Tateoka, has been confirmed (Table 15). However, unlike the Kranz cells of most P.S. grasses, which tend to be wider ra¬ dially than long ( Brown, 1974), the Kranz cells in Eriachne are somewhat longer than wide. This tends to relate Eriachne to the P.S. Danthonieae and Aristideae rather than to the Paniceae. Tateoka (1961b) considered the trans¬ versely elongate, saddle-shaped silica cells of Eriachne to be “panicoid,” but he was using the term in a broad sense, as contrasted with the “festucoid” charac¬ ter of the Aveneae in this case. It is now well established that within the Panicoideae the silica cells are charac¬ teristically dumbbell-shaped, with the long axis of the cells parallel to the long TABLE 15. Species of Eriachne examined for Kranz characters by various investigators: anatomical and photosynthetic characters, and voucher herbaria. Data not attributed are from this study. SI3C Anatomy Herbarium anomala -12.0 P.S. US (Tateoka, 1961) aristidea -15.0 P.S. US (Tateoka, 1961) armitii -12.5 P.S. US (Tateoka, 1961) g la brat a P.S. TEX (Tateoka, 1961) mucronata P.S. NSW (Tateoka, 1961) (C.J.V., 1973) obtusa P.S. TEX (Tateoka, 1961) pollens -1 1.5 P.S. US pulchella P.S. NSW (Tateoka, 1961) stipacea P.S. NSW triodoides P.S. TEX (Tateoka, 1966) triseta P.S. NSW (Tateoka, 1961) 16 other species P.S. (mostly US) (Tateoka, 1961) 72 - he kranz syndrome and its subtypes in grass systematics axis of the leaf. Dumbbell-shaped and saddle-shaped silica cells are very differ¬ ent, so, in this respect, Eriachne is very different from the Panicoideae. The shapes of silica cells in the Danthonieae are too various to be characterized by a single term, and the silica cell type of Eriachne can certainly be matched somewhere among the Danthonieae. Since the Aristideae have dumbbell¬ shaped or spherical silica cells (de Winter, 1965), this character does not seem to relate Eriachne to that tribe (Table 14). The cuneate lodicules of Eriachne are quite different from the more lanceolate ones of Aristideae (Tateoka, 1967) and are more like those of the Eragrostoideae than any other group (Tateoka, 1960). In its long glumes, Eriachne resembles the Danthonieae and Aristideae; in lemma and palea induration, the Aris¬ tideae and Paniceae; and in lemma awn¬ ing, the Danthonieae and Aristideae more than the Paniceae. In fact, the spikelets of some species of Eriachne look very much the same as two-floreted spikelets of Aristida might look. Pheidochloa (see “The Danthonieae") also has such spikelets, but its silica cells are undulate-rectangular, quite different from those of Aristideae or most Eriachne. Eriachne is P.S., like Kranz Eragros¬ toideae, Danthonieae, and Stipagrostis of the Aristideae (Table 15). In contrast, the Paniceae are basically M.S. (Tables 3 and 4). The P.S. Paniceae seem to be rather recently evolved taxa (Hartley, 1958b). 1 conclude that Eriachne is derived from a xeric offshoot of the Danthonieae close to but separate from the origin of the Aristideae. I assume that the Kranz syn¬ drome evolved at the beginning of generic evolution, probably in Australia. THE ERAGROSTOIDEAE The subfamily Eragrostoideae is, so far as known, entirely Kranz. The present sample (Table 16) includes 327 species from 68 genera and all eight tribes. Avail¬ able evidence, dating back to Schwen- dener (1890), also indicates that all species are P.S. (Brown, 1975). How¬ ever, some are reported to be PEP-ck, whereas most of those examined are NAD-me (Brown, 1960; Gutierrez, Gra- cen, and Edwards, 1974; Hatch and Kagawa, 1974), which adds interest to this otherwise apparently uniform group. NAD-me biochemistry seems to be correlated with centripetal chloroplast location and PEP-ck with centrifugal, al¬ though rather few species have been ex¬ amined for either character, especially the biochemical one. Whereas the corre¬ lation seems to be phylogenetically sig¬ nificant in the Paniceae (Table 4), its im¬ port in the Eragrostoideae, if any, is ob¬ scure at this time. That is, some species within the same genus (Bouteloua , MEMOIRS OF THE TORREY BOTANICAL CLUB 73 TABLE 16. Genera of Eragrostoideae containing species reported as P.S. by others , arranged by tribes. no. spp. no. spp. Aeluropideae Leptochlodpsis 2 A el tiro pus 3 Lintonia i Allolepis 1 Munroa i Distichlis 3 Plectrachne 2 Jo uvea 0 Scleropogon 9 Monanthochloe 1 Tetrachne i Reederochloa 1 T ride ns 16 V aseyochloa 1 Triodia 23 Chlorideae Uniola 2 Acrachne 2 Viguierella i Astrebla 3 Bouteloua 1 1 Leptureae Buchloe 1 Ichnurus i Chloris 9 Lep turns 9 Ctenium 2 Cynodon 2 Pappophoreae Dactyloctenium i Blepharidachne i Dine bra i Enneapogon l Eleusine 2 Neostapfia 1 Enteropogon 1 Orcuttia 1 E us tacky s 3 Pappophorum 8 Fingerhuthia 2 Schmidt ia 2 Gouinia 12 Gymnopogon 1 Spain ineae Leptochloa 4 Spartina 9 Lepturidium 1 Melanocenchris 1 Sporoboleae Microchloa 1 Blepharoneuron 1 Oropetium 2 Calamovilfa 4 Pogonathria i Crypsis 3 Rendlia i Heleochloa 1 Schedonnardus i Lycurus 1 Trichloris 2 Muhlenbergia 71 Tripogon i Sporobolus 30 Urochondra 1 Eragrosteae Apochiton i Zoysieae Cleistogenes i Hi lari a 9 Diplachne i Mosdenia 1 Eragrostis 40 Perot is 9 Erioneuron 5 Tragus 3 Zoysia 3 Totals: 8 tribes, 69 genera. 328 species. 74 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Sporobolus , Muhlenbergia, Chloris, Eragrostis, and T ride ns) are NAD-me whereas others are, or seem to be, PEP- ck (Table 1 and unpubl.). In Chloris, the difference is largely correlated with tax¬ onomy; most species are PEP-ck, but those of subgenus Eustachys (Anderson, 1974) are NAD-me. Subgeneric correla¬ tion may also occur within Bouteloua. Complete correlation of C4 photosyn¬ thesis and Kranz anatomy is further sup¬ ported by evidence reported here (Table 17). Reasons for selection of the particu¬ lar species examined varied considerably and are given in the discussions of indi¬ vidual genera. Uniola. Brown and Smith (1974a) de¬ termined the 13C/12C ratios of most species in the small tribe Unioleae. Their results confirmed Yates' (1966) conclu¬ sion that the genus must be divided into two or three genera of two distinct types. Uniola (type species, U. paniculata L.) and Leptochlodpsis are Kranz genera with characters quite typical of the Erag- rosteae. The non-Kranz species are in¬ cluded in Chasmanthium. Since the tribe Unioleae was based almost completely on C. latifolium, the former tribal desig¬ nation is abandoned and Chasmanthium is included in the centostecoid group after Soderstrom and Decker (1973). Aeluropus. This halophytic Kranz genus was investigated because Ban and Waisel (1973) reported that A. litoralis responds to salt concentration around the root system by increasing concentrations of both RuDP-Case and PEP-Case. Plants in no NaCl had PEP-Case too low to be measured. If confirmed, this would be the only species known to have Kranz anatomy but C3 photosynthesis, when growing in low salt soil. Acrachne (Chlorideae), Lintonia (Eragrosteae), and Tretrachne (Chlori¬ deae) are here reported to be Kranz for the first time. TABLE 17. Species of Eragrostoideae examined, arranged by tribes and genera: anatomical and photosynthetic characters, provenances, and voucher herbaria. Data from this study unless otherwise attributed. 813C Anat. Prov. Herb. AELU ROPI DEAE Aeluropus lagopoides -14.3 P.S. Asia TEX Allolepis texana P.S. U.S.A. TEX Distichlis spicata (Bender and Smith, 1973) -13.3 Jouvea pilosa -11.4 P.S. Mexico TEX Monanthochloe lift oralis -14.1 P.S. U.S.A. TEX Vaseyochloa multinervosa -14.6 P.S. U.S.A. TEX CH LORI DEAE Acrachne racemosa -19.3 P.S. Africa PRE MEMOIRS OF THE TORREY BOTANICAL CLUB 75 Table 17 continued. S13C Anat. Prov. Herb. A . verticillata -13.1 P.S. Africa PRE B ante loua aristidoides P.S. U.S.A. TEX B. chondrosioides P.S. U.S.A. TEX B. curtipendula -12.5 P.S. U.S.A. TEX B. eriopoda P.S. U.S.A. TEX B . filiformis P.S. U.S.A. TEX B. gracilis P.S. U.S.A. TEX B. rigidiseta P.S. U.S.A. TEX B. trifida P.S. U.S.A. TEX Buchloe dactyloides -14.3 P.S. U.S.A. TEX Chloris andropogonoides P.S. U.S.A. TEX C. cuculata -15.9 P.S. U.S.A. TEX Cynodon dactylon - 15.3 P.S. U.S.A. TEX Dactylocteniurn aegyptium - 12.2 P.S. U.S.A. TEX Eus ta chys di sti ch ophylla P.S. U.S.A. TEX E. petraea P.S. U.S.A. TEX Gymnopogon ambiguus -13.4 P.S. U.S.A. TEX Leptochloa dubia P.S. U.S.A. TEX Schedonnardus paniculatus P.S. U.S.A. TEX T rich lo ri s pluriflorus P.S. U.S.A. TEX Tripogon s pica t us P.S. U.S.A. TEX E R AG ROSTE AE Eragrostis cilia ne ns is P.S. U.S.A. TEX E. curtipedicellata P.S. U.S.A. TEX E. intermedia -15.6 P.S. U.S.A. TEX E. oxylepis E. spectabilis (Bender and Smith. 1973) -11.0 P.S. U.S.A. TEX E. t rich odes P.S. U.S.A. TEX Erioneuron pilosa -13.4 P.S. U.S.A. TEX E. pulchellum P.S. U.S.A. TEX Leptochlobpsis condensata -13.3 P.S. America US L. virgata -12.8 P.S. America US Lintonia nutans -12.4 P.S. Africa TEX Munroa squarrosa P.S. U.S.A. TEX Plectrachne pungens (Jacobs, 1971) P.S. Aust. NSW P. schinzii (Jacobs, 1971) P.S. Aust. NSW S c le ro pogo n bre vifo li us P.S. U.S.A. TEX Tetrachne dregii P.S. Africa US T ride ns albescens -13.5 P.S. U.S.A. TEX T . elongatus P.S. U.S.A. TEX T. flavus P.S. U.S.A. TEX T . muticus P.S. U.S.A. TEX Triodia basedowii -17.1 P.S. Aust. NSW 76 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 17 continued. 813C Anat. Prov. Herb. T . clelandii P.S. Aust. NSW T. ho st ilis -13.2 P.S. Aust. NSW Uniola panicidata (5) ca. -12.5 P.S. U.S.A. TEX U . pittieri -13.4 P.S. C. Am. TEX LEPTU REAE Ischnurus (Hanson and Potztal, 1954) P.S. Lepturus radicans (Tateoka, 1959) P.S. L. repens -12.7 P.S. Pacific TEX PAPPOPHOREAE B lepha ri da ch ne bigelo vi i P.S. U.S.A. TEX Enneapogon desvauxii P.S. U.S.A. TEX Neostapfia colusana -13.3 U.S.A. TEX Orcuttia californica -13.6 U.S.A. TEX Pappophorum bicolor -13.4 P.S. U.S.A. TEX P. mucronulatum P.S. U.S.A. TEX Schmidtia bulbosa (Giinzel, 1912) Ka 5. pappophoroides (Giinzel, 1912) Ka SPARTINEAE Spartina alternifolia S. cynosuroides (Bender, 1971) 5. pectinacea (Bender, 1971) S. spcirtinae (Johnson, 1964) Ke -13.1 -14.4 -13.4 PS. U.S.A. TEX SPOROBOLEAE Blepharoneuron tricholepis P.S. U.S.A. TEX Calamovilfa brevipilis P.S. U.S.A. TEX C. curtissii P.S. U.S.A. TEX C . gigantea P.S. U.S.A. TEX C. longifolia P.S. U.S.A. TEX Lycurus phleoides -13.8 P.S. U.S.A. TEX Muhlenbergia capillaris -13.2 P.S. U.S.A. TEX M . ernersleyi -11.0 P.S. U.S.A. TEX M. fragilis -13.5 P.S. U.S.A. TEX M. involuta P.S. U.S.A. TEX M. lindheimeri -12.4 P.S. U.S.A. TEX M. mexicana -13.4 P.S. U.S.A. TEX M. minutissima -11.8 P.S. U.S.A. TEX M . montana -13.4 P.S. U.S.A. TEX M . porteri -14.3 P.S. U.S.A. TEX M. reverchoni P.S. U.S.A. TEX MEMOIRS OF THE TORREY BOTANICAE CEUB 77 Table 17 continued. M. sch re be ri M. sylvatica M. utilis M . wolfii Sporobolus airoides S. asper (Bender and Smith, 1973) S. cryptandrus S. heterolepis (Bender and Smith, 1973) S. neglect us S. poiretii (Bender, 1971) S. weigh tii Urochondra setulosa (Hubbard, 1947) ka ZO YS Hilaria belangeri H . mutica Mosdenia phleoides (Tateoka, 1957) ka Perotis patens (deWet, 1960) ka Tragus berteronianus Zoysia japonica Z. mat re I la 5iaC Anat. Prov. Herb. -15.0 P.S. U.S.A. I EX -13.2 P.S. U.S.A. TEX P.S. U.S.A. TEX -12.5 P.S. U.S.A. TEX -13.4 P.S. U.S.A. TEX -12.7 P.S. U.S.A. TEX -13.7 P.S. U.S.A. TEX -12.3 P.S. U.S.A. TEX A E -13.8 P.S. U.S.A. TEX P.S. U.S.A. TEX P.S. U.S.A. TEX -14.7 P.S. Japan TEX -12.3 P.S. Japan TEX Muhlenbergia. Numerous studies of this genus (Soderstrom, 1967; Pohl, 1969) have demonstrated that all species have kranz anatomy. The l3C/12C ratios of annuals, perennials, xerophytes, meso- phytes, and northern species demon¬ strate that all are C4 also (Table 17). Be¬ cause Muhlenbergia is related to Sporobolus and because there are both NAD-me and PEP-ck species in the lat¬ ter (see below), Muhlenbergia is being examined biochemically (by Edwards and Gutierrez) to determine whether it too has both subtypes. Sporobolus. It has now been ade¬ quately demonstrated that there are both NAD-me and PEP-ck species in this genus (Gutierrez, Gracen, and Edwards, 1974; Elatch, kagawa, and Craig, 1975) (Table 1). The survey is inadequate at present to determine whether the two subtypes are correlated with distinct sub¬ generic taxa or not. The presence of both within single genera suggests that perhaps they may be interconvertable during evolution. Bouteloua. This is another genus that contains both NAD-me and PEP-ck species. The available evidence does not suggest that the two subgenera presently recognized are differentially correlated with the two subtypes, because B. cur- tipendula is PEP-ck but B. rigidiseta may be NAD-me and both are in subgenus Antheropogon. All species of subgenus Chondrosium so far examined are NAD-me. 78 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Chloris. This is a fourth genus of the subfamily that probably contains both NAD-me and PEP-ck species. At pres¬ ent, the few species of typical Chloris that have been examined biochemically are PEP-ck, whereas one species of sub¬ genus Eustachys, C. distichophylla, is NAD-me (Table 1). This distinction sup¬ ports separate generic status for Eustachys, as proposed by Anderson (1974). Eragrostis. In this genus also, both C4 subtypes may occur (Table 1). The Old World species E. cilianensis, E. curvula, and E. superba are NAD-me. However, the American E. intermedia and E. trichodes apparently have centrifugal Kranz cell chloroplasts, so they may be PEP-ck. Tridens. For this genus only cytologi- cal observations are available. Whereas T . flavus apparently has centrifugal Kranz cell chloroplasts, those of the other species are centripetal. Triodia. In his recent examination of 23 Triodia species, Jacobs ( 1971) clarified their anatomical status, after the earlier vagueness of Burbidge (1946). He con¬ cluded that all species have Kranz anatomy of a rather peculiar form, and further that they “could perhaps be con¬ sidered as primitive representatives of the tribe Eragrosteae.” He also included data on first seedling leaf morphology, silica cells, bicellular microhairs, iodine staining, lodicule shape, chlorenchyma, starch grains, and chromosome number and size. McWilliam and Mison (1974) have determined that T. irritans is C4, according to PEP-Case level and leaf anatomy. The present study confirms that this genus is Kranz P.S. Plectrachne. Jacobs (1971) also ex¬ amined two species of this genus, which is very close to Triodia. Everything stated about Triodia as a Kranz genus of the Eragrosteae applies equally to Plectrachne . Hilaria. Two species of this American genus have been studied: H . belangeri, a small stoloniferous species which has Kranz anatomy, centripetal Kranz cell chloroplasts, and a 13C/12C ratio of - 13.8; and H. mutica, which also has Kranz anatomy but Kranz cell chloroplasts which change position according, pre¬ sumably, to light intensity! In low light (about 1,000 foot-candles, in a green¬ house) the chloroplasts are dispersed through the cell evenly, but in bright sun¬ light (4,000 to 8,000 foot-candles, and other out-of-doors conditions) they are concentrated in the centripetal regions of the Kranz cells, as in typical NAD-me species. Thus, there seem to be three chloroplast location conditions in Kranz cells of P.S. species. Gutierrez, Gracen, and Edwards (1974, p. 292) stated that the chloroplasts in Kranz cells of Panicum virgatum are “evenly distributed” throughout the cell. Much the same was reported for P. laevifolium, P. dichotomiflorum, and Muhlenbergia lindheimeri. In this study I found it also in species of Eragrostis and Tridens, and in Hilaria mutica. All of these species should be NAD-me, and the movable chloroplasts of H . mutica indicate that “chloroplasts evenly dis¬ tributed” is a modification of the cen¬ tripetal rather than of the centrifugal con¬ dition, which it somewhat resembles. The Eragrostoideae are all Kranz P.S. The rather scanty biochemical and MEMOIRS OF THE TORREY BOTANICAL CLUB 79 cytological evidence indicates that the subfamily is typically NAD-me with cen¬ tripetal Kranz cell chloroplasts. It ap¬ pears that in some genera the PEP-ck subtype has evolved, with accompanying change in chloroplast location. The pre¬ cise significance of the apparent correla¬ tion between biochemical subtype and chloroplast location within Kranz cells is unknown. Nevertheless, variation in the latter can be ascribed to some functional difference. This taxon is quite distinct from other subfamilies, with diagnostically different silica cell and bicellular hair types. Nevertheless, within the large genus Eragrostis there is considerable variation in many of the characters useful in mod¬ em grass systematics. MISCELLANEOUS GRASS TAXA Although my original intent was a thorough study of Panic urn, the Paniceae, and related tribes, ensuing in¬ volvement with anatomical derivations of the Kranz sheaths (Brown, 1975) and with the subtypes of C4 photosynthesis prompted some diversions into taxa from other subfamilies. Such investigations in the Danthonieae, Aristideae, Eriachne, Eragrostoideae, and Andropogoneae have already been discussed, and a study of Uniola has been published ( Brown and Smith, 1974a). Table 18 presents data on the remainder studied, as well as some on other such species from Smith and Brown (1973), Tateoka (1963), and Carolin, Jacobs, and Vesk (1973). TABLE 18. Species of other grass tribes examined for Kranz charac¬ ters by various investigators , arranged by tribes and genera: anatomi¬ cal and photosynthetic characters , provenances, and voucher herbaria. Data from this study unless otherwise attributed. 813C or Synd. Provenance Herbarium Cryptochloa varians OLYREAE -31.1 C. Am. TEX Lithachne pauciflora -29.7 C. Am. TEX Mniochloa strephioides -33.3 Cuba US Olyra latifolia -29.5 Africa PRE O. yucutana -29.8 C. Am. TEX Pariana bicolor PAR1ANEAE -30.3 S. Am. TEX 20 other species (Tateoka, 1961c) Na S. Am. US Leptaspis cochleata PH AREAE -31.1 Africa PRE Phams latifolius -29.6 C. Am. TEX 80 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Table 18 continued. 813C or Synd. Provenance Herbarium PH YLLORACHIEAE Humbertochloa bambusiuscula -30.9 Africa PRE Phyllo rh a ch is sag it tat a -26.0 Africa PRE THYSANOLAENEAE Thysanolaena maxima -27.4 Africa PRE CENTOTH ECEAE Centosteca lappacea -30.9 Africa TEX Me gat achy a macro nata -26.2 Africa PRE Zeugites pittieri -23.6 S. Am. TEX PHAENOSPERMEAE Diarrhena americana -29.5 U.S.A. TEX Phaenosperma fauriei (Tateoka, 1957) Na Asia P. japonica (Tateoka, 1957) Na Asia P. globosa -28.7 Asia US EH RH ARTEAE Ehrharta erecta -26.5 Africa TEX 19 other spp. (Tateoka, 1963) Na Microlaena stipoides (CJV1) Nae Aust. NSW 5 other spp. (Tateoka, 1963) Na Petriella colensoi (Tateoka, 1963) Na P. thomsonii Tetrarrhena 3 spp. (Tateoka, 1963) Na AG ROSTI DEAE Agrostis bergiana -26.4 South Africa PRE A. natalensis —27.7 South Africa PRE ^arolin, Jacobs, and Vesk, 1973. These data augment evidence that the tribes represented are all non-Kranz. Most are tropical forest grasses, and such shade-requiring species, with few excep¬ tions, are non-Kranz. The Ehrharteae are not forest species but, as Tateoka( 1963a) reported, they have non-Kranz leaf anatomy. Prat (1936) reported bicellular microhairs in Ehrharta and Microlaena, and the tribe is characterized by festucoid embryo vascularization (Reeder, 1957; Tateoka, 1963a). These characters and its MEMOIRS OF THE TORREY BOTANICAL CLUB 81 African- Australian distribution make placement of the Ehrharteae difficult. Assignment to the Oryzoideae (Stebbins and Crampton, 1961 ) or to Group 1 1 (see later and Figure 4) seems as logical as any for the present. The non-Kranz 813C ratios of Agrostis bergina and A. natalensis support the in¬ clusion of these South African species in the Festucoideae. Though this study contributes no data useful in placing these miscellaneous genera and tribes sampled, it does pro¬ vide further evidence that they are non- Kranz taxa. DISCUSSION By 1960. the new characters used in the “new systematics" of the Gramineae had reached the point of treatment in general reviews (Jacques-Felix, 1962; Prat, 1960; Stebbins and Crampton, 1961; Auquier, 1963). These were initiated by the 1959 symposium. “The Natural Classification of the Gramineae" (Recent Advances in Botany, 1961 ) and paralleled a resurgence of interest in grass leaf interiors. Rhoades and Carvalho (1944) had re¬ ported that the Kranz cells of Zea mays contain, compared to mesophyll cells, large specialized plastids that store starch. Kortschak and coworkers in Hawaii had been building toward the discovery of C4 photosynthesis in sugarcane (Burr, et al., 1957). Hodge, Mclean, and Mercer ( 1955) had examined the chloroplasts of Zea mays by electron microscopy and reported that those of the Kranz cells lack grana. Badenhuizen, Bartlett, and Gude (1958) had attempted to determine en¬ zymatic differences between the mesophyll and sheath cells of Cynodon dactylon (Eragrostoideae) with respect to starch synthesis, which normally occurs only in the Kranz cells. Brown (1960) observed differences in chloroplast location within Kranz cells. Johnson (1964) examined leaf chloro¬ plasts of numerous grass species by elec¬ tron microscopy and found essentially agranal Kranz cell chloroplasts in An- dropogoneae and most Paniceae but large grana in chloroplasts of Kranz cells in Eragrostoideae. Meanwhile, techniques for determin¬ ing 13C/12C ratio (Wickman, 1952; Park and Epstein, 1961), postillumination C02 burst (Decker, 1959), and C02 compen¬ sation point (Moss, 1962) were de¬ veloped. Between 1965 and 1970, models of C4 photosynthesis were developed (Hatch and Slack, 1970) and that condition was correlated with Kranz leaf anatomy in the 10 angiosperm families known to be Kranz since 1920. Between 1970and 1975, three subtypes of C4 photosynthesis were characterized (NADP-me, NAD-me, and PEP-ck) (Hatch and Kagawa, 1974; Gutierrez, Gracen, and Edwards, 1974; Hatch, Kagawa, and Craig, 1975). A preliminary survey of 13C/I2C ratios in the Gramineae (Smith and Brown, 1973) demonstrated many C3 species of Paniceae. And Brown (1975) characterized two anatomical sub- types of Kranz anatomy, the P.S. type having the Kranz tissue derived from the parenchyma sheath, and the M.S. type with the Kranz tissue evolved from the 82 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS mestome sheath of non-kranz grasses. Brown and Gracen (1972) and Gutierrez, Gracen, and Edwards (1974) related NADP-me and PEP-ck photosynthesis to centrifugal chloroplast position within kranz cells, and N AD-me to centripetal. Thus, the three subtypes of C4 photosyn¬ thesis were correlated with three sub- types of kranz leaf anatomy and cytol¬ ogy. Brown (1958) had characterized the Panicoideae as having some species with and some without an endodermis (mes¬ tome sheath), and the Eragrostoideae as always having a mestome sheath. Now, the evolutionary and phylogenetic sig¬ nificance of those observations is accen¬ tuated by the discovery of correlations between anatomical and C4 photo¬ synthetic subtypes. This is particularly germane to analysis of the Paniceae, a tribe that contains non-kranz genera, subgenera, sections, groups, and species, as well as all three kranz subtypes. Also amenable to such analysis are the genus Panicum itself (s. lat.), which also con¬ tains all four conditions, and the tribes Danthonieae and Aristideae, which con¬ tain both non-kranz and kranz genera. The data accumulated in this work especially, but other scattered observa¬ tions also, demonstrate that C3 photosyn¬ thesis is indeed always associated with non-kranz anatomy and C4 always with kranz. The only exceptions are the A triplex hybrids (Bjorkman, et al., 1971) and the unknown condition in the South African grass Alloteropsis semialata (s. lat.). The only reported “intermediates” between C3 and C4, Mollugo verticellata (kennedy and Laetsch, 1974) and Steinchisma hians (Brown and Brown, 1975), are C4-like C3 species. It seems evident that no species con¬ tains both kranz and non-kranz sub¬ species, although many genera contain species of both types. This, then, is a specific but not necessarily a generic dif¬ ference. 1 assume that it takes at least as long for the kranz condition to evolve from the non-kranz as for any other “good” specific characteristic to evolve. Though intermediates are known ( Mollugo verticellata , Steinchisma hians, and evidently Chamaesyce acuta), in such cases the condition appears to be uniform throughout the species. It can be concluded, therefore, that non- kranz/kranz status is a very good char¬ acter for specific differentiation. The implications of this study for the various tribes and for Panicum have al¬ ready been discussed. Here, evolution of the kranz syndrome within the Gramineae and major events in the evolu¬ tion of the family are considered. Figure 5 presents conclusions on the evolution of the kranz syndrome in the Gramineae. Figure 4 presents an evolutionary scheme for the family itself. I shall discuss the latter first because the kranz syndrome, regardless of how often it has evolved within the family, is limited to the most advanced subfamilies. During the past 45 years many non- morphological characters have been found useful in grass systematics (Steb- bins and Crampton, 1961; Prat, 1960; Auquier, 1963), but some are useful only within subfamilies or tribes and some are too variable to be considered major guides to the evolution of the family. It is my considered opinion that the most sig¬ nificant evolutionary changes, in order, may have been as follows. The original grasses, like all angio- FIGURE 4. Evolutionary' scheme of the Gramineae . MEMOIRS OF THE TORREY BOTANICAL CLUB 83 UJ < UJ Q 5 U z < 0. c o 'S d C/5 C/5 CO c S CL CO 4/ 03 4/ C d> 03 s O 0> 03 'v. 4/ _CJ O 0> u 4/ 00 0 D. 03 4/ TO -C *—> c O E 03 < H 2 CL < < < O v u 03 a C > ‘5 _ s & 1_ <03 03 0 4/ 03 D 35 >, „ o co N /- 1> 03 03 1> D D •- CJ 0/ *— C r- £■00 £ § = >- H O u o C/5 UJ C/5 DC < X QC < _J UJ u 03 4/ a a> a> 03 E a> >. Cl 03 CJj 0 03 0 t: cd 03 C 03 a> a. N a> XL "O a-> a> >» 03 1— •— Of) u. u SZ SZ 03 >> ^5 O CL UJ z -J o_ D O OL O 4/ 4/ 03 45 03 4» 03 o *y • — -«r J= x: O 4> O 03 o o >- 4/ 03 4/ 4/ 03 4> 4> 1 E c i: _c 03 'S £ < S C/5 iZ T as 4) 03 41 4) £? 4> 03 C/5 03 4/4/4/ u c •a r o o o " O t D. g s -g a: 4/ .2 E o -- 2 O 2 Q < U « ffl Cl D 4/ UJ m «/ S «s 4/ 4> Q 4/ 03 03 __ C-* 4/ 4/ O 3 « c X c^ *-• 4/ O 4/ ’C > D- U. h- < Agrostideae x = 6 ±L LARGE Phalarideae — Monermeae URFORM 84 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS sperms probably (Ehrendorfer, et al., 1968), had a basic chromosome number of 6 ± 1 and the chromosomes were rela¬ tively large. The extant subfamily with these characteristics is the Pooideae. The taxa of this subfamily generally grow in mesic, cool to cold regions or seasons (cold, temperate, arctic, alpine, and wet cool winters). The first major evolutionary change was the establishment at the tetraploid level of a new range of basic chromosome numbers, x = 9-15, and the chromo¬ somes were small. This characterizes all other grass subfamilies. The group of tribes with these characteristics, but otherwise much like the Pooideae, I have designated as Group I. The second major change was the ac¬ quisition of bicellular microhairs. All subsequent subfamilies possess these unique structures, on the leaf epidermis at least. Correlated with this change was invasion of the tropics, especially the tropical forests. The extant taxa exhibit¬ ing such additional changes, the miscel¬ laneous tribes constituting Group II of Figure 4, have been variously treated by systematists (Tateoka, 1957b; Stebbins and Crampton, 1961; Parodi, 1961; Calderon and Soderstrom, 1973; Steb¬ bins, 1972; Soderstrom and Decker, 1973; Hubbard, 1973). I lump them merely because they possess bicellular hairs but not the next evolutionary ac¬ quisition. The third major change was develop¬ ment of a mesocotyl (Reeder, 1957, 1961, 1 962). The three preceding groups do not have this structure; the three subsequent subfamilies do. It is only among the latter that the Kranz syndrome has evolved, either in all three subfamilies or else only in two if the Eragrostoideae originated as Kranz grasses. The Arundinoideae are usually consi¬ dered to be a primitive group. Of these, the temperate tribe Danthonieae may be most like those grasses in which the em¬ bryonic mesocotyl evolved. In numerous characters, such as silica cell and lodicule shapes, the Danthonieae resemble the Panicoideae and Eragrostoideae, and spikelet character trends lead from Danthonieae to Arundinelleae in the Panicoideae (Table 14). This scheme (Figure 4) is based almost entirely upon a sequence of what can be considered the most significant and con¬ servative evolutionary changes from simple to complex. Some previous pro¬ posals have assumed that the Arun¬ dinoideae (Stebbins, 1956, 1972; Prat, 1960) or some tribes of Group II (Tateoka, 1957b) may most nearly rep¬ resent the ancient forms of Gramineae. But in order to derive the Pooideae from the Arundinoideae, reduction by loss of the mesocotyl and bicellular hairs, reduc¬ tion in basic chromosome number, and significant increase in chromosome size would have to be proposed. Thus, the Group II tribes would be the oldest or next most ancient, and the Group I tribes more ancient than the Pooideae. That scheme would also permit some Pa- anicoideae to represent more ancient grass types. There is considerable merit for consid¬ ering the Arundinoideae to represent the most primitive type of Gramineae. Cer¬ tainly most tribes of Groups I and II and some Panicoideae do seem to be rem¬ nants of ancient taxa, and the Pooideae MEMOIRS OF THE TORREY BOTANICAL CLUB 85 can be interpreted as recently-evolved, greatly reduced taxa which have oc¬ cupied recent cool and cold, mostly northern hemisphere environments. Such schemes are interesting but all are largely hypothetical and based mostly on comparison of extant taxa. Without numerous early Tertiary or late Cretace¬ ous fossils, which are almost completely lacking, the early forms of grasses and the actual evolutionary sequences in the fam¬ ily may never be known with certainty (Stebbins, 1972). FIGURE 5. Evolutionary scheme of the Kranz syndrome in the Gramineae. Eragrostoideae NAD-me, PEP-ck P.S. Aristida NADP-me D.S. Stipagrostis P.S. Pheidochloa P.S. Alloeochaete P.S.? As the not he rum P.S. Eriachne P.S. Arundinelleae, etc. MS. Paniceae NADP-me M.S. Digitaria NADP-me MS. Alloteropsis M.S. Neurachne M.S. Andropogoneae NADP-me M.S. Panic um NADP-me M.S. Panicum NAD-me P.S. ‘Grandia” Paniceae PEP-ck P.S. Paniceae NAD-me? P.S. Melinideae P.S. 86 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS Figure 5 reflects the conclusion that the Kranz syndrome has evolved several dif¬ ferent times during the histories of the subfamilies having an embryonic mesocotyl. Because all the Eragrostoideae are Kranz P.S. (Table 17), it can be assumed that the original eragrostoid grasses were already Kranz and that the subfamily must have evolved long ago in order to have permitted subsequent evolution of its constituent tribes. More recently, the non-Kranz African genus Sartidia (Aristideae) probably evolved from non-Kranz Danthonieae. From Sartidia, Stipagrostis evolved as a desert genus with Kranz P.S. anatomy. But Aristida originated separately. Mainly Kranz M.S., it also includes species with a double Kranz sheath unique to that genus. Since the one spe¬ cies of Aristida examined has the NADP-me subtype of C4 photosyn¬ thesis, which correlates with the M.S. subtype of Kranz anatomy, Aristida and Stipagrostis seem to represent two dis¬ tinct evolutions of the Kranz syndrome (Figure 3). The danthonioid genera Pheidochloa of Australia and Alloeochate and Asthenatherum of South Africa are all P.S. and may represent one, two, or three separate evolutions of the Kranz syn¬ drome. Within the Panicoideae there are non-Kranz as well as Kranz tribes. The non-Kranz genera of Paniceae are of var¬ ious sorts; most are hydrophytes or forest plants. The latter are very similar to the numerous non-Kranz species of Panicum. From Kranz M.S. Paniceae, or from some common ancestor, evolved the completely Kranz Andropogoneae, which Hartley (1958a) considered to be the most recently evolved tribe of the Gramineae. The Melinideae are Kranz P.S. and may represent a distinct evolution of the Kranz syndrome. Or they may be closely related to the typical NAD-me sections of Panicum, and perhaps to any other NAD-me genera of Paniceae. The PEP-ck, P.S. Paniceae (the Brachiaria group) either represent a dis¬ tinct evolution of the Kranz syndrome or else were derived recently from NAD- me, P.S. Paniceae such as occur in Panicum (Table 4 and Figure 1). It seems likely that very recent evolu¬ tions of the M.S. subtype have occurred in South America within the group “Grandia” of Panicum. Most other Kranz genera of Paniceae are M.S. and must represent an early evolution of the syndrome. However, the Australian genus Homopholis may represent the non-Kranz ancestor of the worldwide genus Digitaria , and the Australian non-Kranz genus Thyridolepis may rep¬ resent an ancestral form of the Australian Kranz genera N eurachne and Paraneurachne (Figure 5 and see later). It is quite clear that the non-Kranz and Kranz forms of Alloteropsis semialata in South Africa are very closely related; they are almost indistinguishable mor¬ phologically. At this time it can be hypothesized that the Kranz syndrome evolved recently in the South African non-Kranz population, though long enough ago for the Kranz form to spread to China and Australia. It is possible, of course, that reverse evolution occurred and that in South Africa the non-Kranz MEMOIRS OF THE TORREY BOTANICAE CLUB 87 form evolved from the Kranz form, or that the two forms are not closely related but reflect convergent evolution. Both the Eragrostoideae and An- dropogoneae seem to be uniform in leaf anatomy, P.S. and M.S. respectively. But, whereas the Andropogoneae seem to be uniformly NADP-me, the Eragros¬ toideae contain both NAD-me and PEP-ck species. This could be inter¬ preted as indicating the biochemical and anatomical isolation of M.S. , NADP-me taxa, and the close relationship of P.S., NAD-me and P.S., PEP-ck taxa. In the Eragrostoideae most species seem to be NAD-me, so that the few PEP-ck species seem to be derived from some recent or extant NAD-me ancestors (Table 1). Therefore, it can be proposed that the P.S., NAD-me subgenus of Panicum and the P.S., PEP-ck genera of Paniceae may also have had some common, NAD-me ancestor ( Figure 1 ). On the other hand. Hatch, Kagawa, and Craig (1975) have proposed biochem¬ ical schemes which seem to indicate that the NAD-me subtype is more complex than the PEP-ck (their PCK-type). At least, the former exhibits, within the Kranz cell mitochondria, biochemical reactions that seem to occur outside the plastids and mitochondria in PEP-ck species. However, the PEP-ck subtype may be, in fact, a biochemical derivative of the NAD-me subtype, as it certainly seems to be from evolutionary considera¬ tions. How many times has the Kranz syn¬ drome evolved within the Gramineae? The M.S. Panicoideae probably had at least one evolution of the Kranz syn¬ drome long ago. But Alloteropsis , Neurachne , and the group "Grandia” of Panicum indicate three apparently recent and independent evolutions of the syn¬ drome. It seems likely that Steinchisma (S. hians/ S. milioides at least) may be in some middle stage of evolving from non-Kranz to Kranz. The P.S., NAD-me condition in Panicoideae may have had a single an¬ cient origin. Whether the P.S., PEP-ck type is derived from the NAD-me type or evolved separately in non-Kranz Paniceae is presently unknown. In the Danthonieae, the Kranz syn¬ drome evolved at least once to produce the genera Asthenatherum , Al- loeochaete, and Pheidochloa. In the Aristideae, Aristida and Stipagrostis seem to be the results of two evolutions of the syndrome. The Eragrostoideae probably all derive from one ancient evolution of the syn¬ drome, perhaps the first in the family, and possibly among ancestors in common with the Danthonieae. Thus, within the Gramineae it can be proposed that there have been at least seven separate evolutions of the Kranz syndrome. The actual number may be considerably higher. It has often been stated (Downton, 1974b) that the Kranz syndrome is an adaptation to more xeric habitats (high temperatures, high insolation, and low soil moisture). Although there are certainly many cases in which this is debatable, in the Gramineae it seems to be generally true. There are, however, xerophytic non-Kranz genera ( Cleistochloa , Dimor- phochloa, Thyridolepis, etc.) and emergent aquatic Kranz species (in Oryzidium, Paspalum, etc.) in the family. 88 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS It is now possible to address the further question: Is any subtype of the Kranz syndrome in the Gramineae more suc¬ cessful as an adaptation to xeric condi¬ tions than the others? The grass taxa con¬ taining the species and genera native to the most xeric environments are the Eragrostoideae, the Aristideae, and, among the Paniceae, the subgenus Panicum. In the Aristideae, non-Kranz Sartidia is mesophytic. Kranz Aristida seems to be basically a modified M.S., N ADP-me taxon, the species of which range from mesic to xeric habitats. The third genus, Stipagrostis, is P.S. and is native to very arid regions of Africa and southern Asia. It is well known (Hartley and Slater, 1960) that the Eragrostoideae include most of the grass species of very arid regions. They are all P.S. and mostly NAD-me, although PEP-ck species are known (Table 1). Most Paniceae are M.S., doubtlessly NADP-me, and mesophytic (Hartley, 1958b). Probably the most xerophytic species of the genus are in section Dura of the P.S. subgenus Panicum. These are true desert species and probably NAD- me. Numerous other species of the sub¬ genus are also found in rather arid envi¬ ronments. Therefore, it can be proposed that among the Gramineae those species oc¬ cupying the most arid regions and grow¬ ing during the hot dry season have ihe P.S. subtype of Kranz leaf anatomy snd the NAD-me subtype of C4 photosyn¬ thesis. In 1958 I proposed six types of grass leaf anatomy, three non-Kranz and three Kranz. There is now reason for modify¬ ing the designations of the non-Kranz types because some of them occur within the Panicoideae, but that will not be at¬ tempted here. The designations of the Kranz types (chloridoid, panicoid, and aristidoid) also deserve reconsideration in light of recent studies. I propose to change from taxon-based terms to de¬ scriptive and evolutionary ones because the former have erroneous implications. Chloridoid (or eragrostoid) anatomy, typical of all species of the Eragros¬ toideae, should be referred to as the P.S. type, whether occurring in that subfam¬ ily, the Panicoideae, or the Arun- dinoideae. Panicoid anatomy should be referred to as the M.S. type, even though it is, so far as known, restricted to the Panicoideae. Within the Panicoideae, a wide variety of anatomical types occur: perhaps more than one non-Kranz type, as well as Kranz M.S. and two types of P.S. Aristidoid anatomy is restricted to the genus Aristida as presently delimited (de Winter, 1965). However, non-Kranz and the P.S. types also occur within the tribe Aristideae. Therefore, I suggest that this Kranz type, as it occurs in Aristida , be designated the D.S. (for “double sheath”) type, parallelling M.S. and P.S. Other subtypes of Kranz leaf anatomy occur in other families and have been named (Johnson and Brown, 1973; Brown, 1975). The anatomical evolutionary steps from non-Kranz to the M.S. type now seem clear. Brown (1975) reported that a Kranz sheath can evolve from the mes- tome sheath of non-Kranz grasses. Now, with closely related non-Kranz and Kranz taxa known in Alloteropsis , Panicum (group “Grandia”), and MEMOIRS OF THE TORREY BOTANICAL CLUB 89 Thyridolepisl N eurachne , the sequence of anatomical changes is evident. First the mestome sheath cells become larger, thinner walled, and acquire chloroplasts. Then C4 photosynthesis evolves, as in Alloteropsis semialata and Panic um petersonii , with slight modification of the parenchyma sheath. At about this same time there is evolution (perhaps in a rapid, single step) of the closely-spaced intercalary bundles typical of all Kranz grasses. This change seems to be neces¬ sary to increase the amount of Kranz tis¬ sue relative to mesophyll for biochemical balance of the two steps in C4 photosyn¬ thesis. Distinctive cells do not represent an intermediate step in the evolution of intercalary bundles because they occur in taxa which must be derivatives of an an¬ cient evolution of the Kranz syndrome. The persisting parenchyma sheath, as it occurs in Alloteropsis semialata and Panicum petersonii, would inhibit the circulation of molecules between mesophyll and Kranz tissue. In N eurachne munroi and N. muelleri, the parenchyma sheath cells seem to be greatly reduced in size. Finally, as is true in nearly all M.S. species, the paren¬ chyma sheath is lost completely, so that mesophyll and Kranz cells are in direct contact. It can be concluded, therefore, that any Kranz M.S. taxon which is closely re¬ lated to a non-Kranz taxon and has a per¬ sisting parenchyma sheath is an example of recent evolution of the Kranz syn¬ drome. Among Kranz P.S. taxa there is no such anatomical marker known that might indicate recently evolved taxa. Steinchisma (Panicum) hians/S. milioides is C3 although intermediate in a number of characters. It has not evolved the intercalary bundles. What is known seems to indicate that anatomical changes toward Kranz anatomy precede biochemical changes toward C4 photo¬ synthesis. Taxonomically , the difference be¬ tween the Kranz syndrome and the non- Kranz condition is at the least a specific one. There is no known species contain¬ ing both Kranz and non-Kranz sub¬ species (Alloteropsis semialata and its variety eckloniana are actually at least specifically distinct; Ellis, 1974b). Even the known intermediates between C3 and C4 are specifically distinct (Mollugo verticillata , Steinchisma hians, Cham- aesyce acuta). On the other hand, the difference is not necessarily a generic one; there are too many genera and sec¬ tions containing both sorts, especially among dicotyledons. This degree of taxonomic distinction would seem at least commensurate with that of what are recognized as inter¬ specific differences in more traditional characters. Ten genetic changes or more are necessary to achieve the cytological, anatomical, and physiological transfor¬ mation from non-Kranz to Kranz. Furthermore, the amount of time re¬ quired to achieve such an evolutionary change must be at least as great as that needed for interspecific differentiation in more traditional characters. It has recently been demonstrated among a few species of dicotyledons (Bjorkman, et al., 1975) that Kranz species are not exactly alike in tempera¬ ture optima for maximum growth, and that such differences also exist between 90 THE KRANZ SYNDROME AND ITS SUBTYPES IN GRASS SYSTEMATICS (various) Kranz and (one) non-Kranz species. Photosynthetic membrane characteristics seem to be most critical in these differences. One Kranz species, Tidestromia oblongifolia, has photo¬ synthetic membranes highly specialized for extremely high temperatures, whereas two Kranz species of A triplex have membranes less extremely specialized. The latter can, therefore, grow much better than T. oblongifolia at somewhat lower temperatures. It seems likely that Kranz grass species with wide climatic ranges, such as Panicum vir- gatum, P. capillare, Setaria lutescens, Digitaria sanguinalis , and Schiza- chyrium scoparium, have photosynthetic membranes of the less specialized type. On the other hand, species of the desert section Dura of Panicum may have photosynthetic membranes specialized for very high temperatures. It is likely that such differences in photosynthetic membranes also exist among non-Kranz grass taxa. If so, that could explain restriction of the Pooideae and the Group I tribes of Figure 4 to cool growing seasons, but of certain other non-Kranz groups such as the Bam- busoideae and Oryzoideae (most tribes of Group II in Figure 4) to warm growing seasons. It is assumed that photosynthe¬ tic membranes adapted for high tempera¬ ture efficiency (but of low efficiency in cool temperatures) are typical of certain non-Kranz as well as most Kranz taxa. It also seems likely that some Kranz taxa have evolved photosynthetic mem¬ branes adapted for efficiency in cool temperatures and/or in dense shade (see discussion under "The Andro- pogoneae”). MEMOIRS OF THE TORREY BOTANICAL CLUB 91 ACKNOWLEDGMENTS Like any scientific report, this paper incorporates results of the efforts of many predecessors and contem¬ poraries. Among the latter are a number of correspondents who have actually contributed data and ideas directly, and collegues who have worked with me gathering and evaluating data. Most predecessors who have worked on the systematics of the Gramineae and on leaf anatomy are mentioned in the text. Contemporaries are also mentioned there, but the following 1 thank especially. Doctor Bruce N. Smith, formerly at the University of Texas and now at Brigham Young Uni versity, directed the investigation of l3C/12C ratios, determining many of them himself, and was co-director of the National Science Foundation grant that supported especially that portion of the research. His contribution was, ot course, very significant. Doctor Gerry Edwards of the University of Wisconsin, in publication, correspondence, and personal discussion, contributed data as well as some insight into the biochemistry of C4 photosynthesis and its relation to anatomy. Doctor Surrey Jacobs of the National Herbarium. Sydney was very helpful in selecting and transmitting Australian grasses for this study, as well as other materials. His advice and suggestions by mail are very much appreciated and have contributed significantly to some of the ideas presented here. Mister R. P. Ellis of the National Herbarium, Pretoria has added greatly to my knowledge of Alloteropsis and other African genera. Doctor B. de Winter and the National Herbarium, Pretoria lent collections of numerous African grass species. Doctor R. H . Brown of the University of Georgia kept me abreast of his study of intermediacy in Panicum milioides and shared that investigation with me. Doctor T. R. Soderstrom of the Smithsonian Institution provided some meaningful agrostological discus¬ sions and arranged a loan of numerous specimens from the U. S. National Herbarium which contributed greatly to the completeness of my study. I am also grateful to him beyond expression for detailed and careful review of the entire manuscript. Doctor M. D. Hatch of C.S.I.R.O., Canberra provided prepublication results of studies made in his laboratory. Doctor B. Rosengurtt of the Universidad de la Republica. Montevideo sent many South American speci¬ mens. Doctor J. Bosserofthe Museum National d' Histoire Naturelle. Paris supplied material ofthe rare Madagas¬ can Panicoideae, Cyphochiaena, Lecomtella, and Pseudechinolaena . I thank the National Science Foundation for Grant GB-40I0I , which made much of this research possible. LITERATURE CITED Anderson, D. E. 1974. Taxonomy of the genus Chloris (Gramineae). Brigham Young Univ. Sci. Bull., Biol. Ser. 19(2): 1—133. Auquier, P. 1963. 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