A G N : CH A ASE ‘ : ’ MN FIRST BOOK OF GRASSES Che Mural CertBook Series Epritep By L. H. BAILEY Bailey: ScHoot-Book oF FARMING. Carleton: THE SMaLL GRAINS. Chase: First Book oF GRASSES. B. M. Duggar: THE PHYSIOLOGY OF PLANT PRODUCTION. J. F. Duggar: AGRICULTURE FOR SOUTHERN SCHOOLS. J. F. Duggar: SouUTHERN FIELD CRops. Fisk: Tar Boox oF Icr-CREAM. Gay: BREEDS oF LIVE-STOCK. i Gay: PRINCIPLES AND PRACTICE OF JUDGING LivE-STOcK. Goff: PRINCIPLES OF PLANT CULTURE. Gourley: TExT-Book oF PoMOLOGY. Guthrie: THE Book oF BuTTER. Harper: ANIMAL HUSBANDRY FOR SCHOOLS. Harris and Stewart: THE PRINCIPLES OF AGRONOMY. | Hitchcock: TExT-Book oF GRASSES. Jeffery: TExT-Book or LAND DRAINAGE. Jordan: FREDING OF ANIMALS, REVISED. Livingston: FIELD Crop PRODUCTION. Lyon: Sorts AND FERTILIZERS Lyon, Fippin and Buckman: Sots; THEIR PROPERTIES AND MANAGEMENT. Mann: BEGINNINGS IN AGRICULTURE. Montgomery: THE Corn Crops. Morgan: Fintp CROPS FOR THE COTTON- BELT. Mumford: Tur BREEDING oF ANIMALS. Piper: FORAGE PLANTS AND THEIR CULTURE. Sampson: EFFECTIVE FARMING. Smith: AGRICULTURAL METEOROLOGY. Stubenrauch, Wood and Booth: HorTICULTURE FOR SCHOOLS. Thom and Fisk: THE Book oF CHEESE. Warren: ELEMENTS OF AGRICULTURE. Warren: Farm MANAGEMENT. Wheeler: MANURE AND FERTILIZERS. Whitef PRINCIPLES OF FLORICULTURE. Widtsoe: PRINCIPLES OF IRRIGATION PRAC- TICE. FIRST BOOK OF GRASSES, ae STRUCTURE OF GRASSES EXPLAINED FOR BEGINNERS RY AGNES CHASE; ASSISTANT AGROSTOLOGIST, UNITED STATES DEPARTMENT OF AGRICULTURE New York THE MACMILLAN COMPANY 1922 All rights reserved CoPpyRIGHT, 1922 By THE MACMILLAN COMPANY Set up and electrotyped. Published November, 1922. Printed in the United States of America PREFACE Of all plants grasses are the most important to man. The different kinds are known by very few even among botanists. This is largely because they are supposed to be very difficult. When the struc- ture of grasses is clearly understood, they are not more difficult to study than are other plants. The method here offered has been used by the author for some years in teaching special students. The introduction explains the method followed. The body of the primer consists of twelve lessons, graded from the simplest to the most complex. Each lesson is accompanied by figures bringing out the facts in the text. The difference in the size of the flowering organs is so great that the figures are not drawn to the same scale. The organs are enlarged as much as necessary to illustrate the char- acter discussed. ~ Grasses of the United States are used for the lessons and the commoner ones are selected so far as possible; however, our native grasses cover so wide a range that the principles laid down in the lessons are ws pheable to grasses generally. AGNES CHASE. Washington, D. C., August 10, 1922. TABLE OF CONTENTS PPAR NR NSA TS ey eI cit ssi en ty See owas ube 1-7 Use of technical terms, 2; Use of Latin names, 4; Tools needed, 6. Desson [.....:.. PP Ae Meamnnteniy ate ha oo eels ae este 8-16 The grass family, 8; Summary, 16; Review, 16. nr aMM NN tes ab oes umes ca ies wince wisn ele -17-20 The spikelet and the inflorescence, 17; Summary, 19; Review, 20. Beem Shs stone Sea ia eta katie ss ates cea 21-24 Modifications of the spikelet, 21; Summary, 24. ORNL Bh SS aE aS aks wala vu kcal ale ele 25-33 Pediceled spikelets of few to many florets, 25; Sum- mary, 33; Review, 33. LA SATAN SS Sag oeend sta) ga RT Me 34-41 Sessile spikelets in two-sided spikes, 34; Summary, 41; Review, 41. a 0 Ga teed ff Se a ge Maas La en aes Same 42-45 Pediceled spikelets with large glumes and other modi- fications, 42; Summary, 45; Review, 45. MeO NRE rate sr hy eS FL ad sine RNs ale 46-53 Pediceled one-flowered spikelets, 46; Summary, 52; Review, 53. | Peter Eber i.) 7 ae mie Sah at od ai ees 54-60 _ Sessile spikelets in one-sided spikes, 54; Summary, 60; Review, 60. Riper ee ame ae i st co UN ny tie ae 61-67 Diversely specialized spikelets, 61; Summary, 67; Re- view, 67. Vil Vill TABLE OF CONTENTS LESSON OG Ue esl 68-78 Spikelets with membranaceous glumes and hardened fruits, 68; Summary, 77; Review, 78. PMSSON OE RU Oy oe ae caus ee oe 79-88 Paired spikelets with hardened glumes and thin lemmas, 79; Summary, 88; Review, 88. DISSONANT es dee We cee ee 89-94 Highly specialized unisexual spikelets, 89; Summary, 94; Review, 94. DIAGRAMMATIC SUMMARY OF THE PRIMARY CHARACTERS OF THE ERIBES 2 0024 bse eee a 95-99 Series 1, Poate, 95; Series 2, Panicate, 98. GENERAL INFORMATION FOR THE BEGINNER........... 100-115. Outline for study of a grass plant, 100; Books, 104; Botanical names, 108; Classification of plants, 111; Position of grasses in the plant kingdom, 113; Grasses in relation to man, 114. LIST OF ILLUSTRATIONS Fic. PAGE 1. Vegetative part of a grass plant; part of leaf opened out.. 9 2. Typical complete flower showing calyx, corolla, stamens FMMUEN SA) eee i. te oe SU i ck wala aes 9 3. Grass flower, showing stamens and pistil and the rudi- Mem NOTA! CAVElOpe 1 Si bal eke wen wes 10 Peete at Howerme TIME... sas ye. be es 11 Enews OF 2 OTA be et ee rs bee ek 11 fweiaeram OF 2 Howerne branch)... 6b. 0. 12 peer, OF. 4 etics spikelet.. 2.7.0. oe ee. 12 Beoeeemeralived SpIKeleh... 1... oc ee oe ea 13 9. Base of plant and underground parts, roots and rhizomes, ORME CTISES clas a. Set hae Bae ky Gale ee 14 10. Forms of inflorescence; A, panicle; B, raceme; C, spike.. 18 11. A, several-flowered spikelet of Bromus secalinus; B, single ORE per ea Ua nel ie chk Nigh ate Les Tee ae 25 12. A, spikelet of Festuca ovina; B, lemma detached........ 26 i epicclet, of Panicularia seplentrionalis.. .. 2 .0...6.... 2E espn i Or FO DICLEMSIS. oe Pi SR oe a te 27 Pee aes Of Picurepogon: COMJOTINCUS ... oo es oo eos eS Zt Ghee Oi F010 (GUA. e ee ES RN Sc wale 28 Perens ci Collea pappophoroiles. . . on ee 28 18. A, spikelet of Phragmites communis; B, floret. .... Jere 28 Po euceret, Of WCliCdMUNCN. 28 nes 2) occ Shea ee 29 20. Florets of Pappophorum vaginatum... 0... oe ee ee 29 21. A, part of a panicle of Cynosurus cristatus; B, sterile pmiccien «fertile Spikelehe oes ee. be 30 22. A, fascicle of three sterile and one fertile spikelet of Achyrodes aureum; B, fertile spikelet............... 31 23. Pistillate and staminate spikelets of Distichlis spicata... 32 ix o2. LIST OF ILLUSTRATIONS PAGE . Staminate and pistillate spikelets of Scleropogon brevi- TOWUB. SGM een Pag ini, Nn, es AO ahr 32 . A, part of a spike of Agropyron repens; B, part of rachis seen from the edge, all but two spikelets removed.... 34 . opikelet of Triticwmn eshivum. oo. 2. 30 . Part of a spike of Lolwwm multifiorum.......>. 0/0. ee 36 . A, part of a spike of Lepturus cylindricus; B, diagram of rachis, spikelets removed; above, diagram of single POUNE ye Oey Ce Oe 37 . A, pair of spikelets of Elymus mrginicus; B, diagrammatic figure of the pair of spikelets. ......../.. ...033 38 . Joint of spike of Hordeum nodosum. .../......2) ee 40 . A, spikelet of Avena fatua; B, floret. .:...:. 0. ee 42 Spikelet of Trisetum spicatum. 2... 0.2 2 43 . Spikelet of Danthonia spicata; floret above............ 43 . A, spikelet of Notholcus lanatus; B, pair of florets...... 44 . Spikelet of Calamagrostis canadensis............ 2.0 90an 46 . Sprkelet ‘of Agrostis Memalis.... once cn ok ee 47 . Spikelet of Sporobolus airoides.......5. 0.5.0... AT . Spikelet of Phleum pratense; floret above.............. 48 » Spikelet of Alopecurus geniculatus........-....>..2 48 . Pair of spikelets, sterile and fertile (spread apart) of 3 Lycurus phleoidese's oo os ae dies ay koe 5s 49 . Spikelet of Muhlenbergia folidsa:.........02 .. 758 oe ea . A, spikelet of Muhlenbergia Schreberi; B, branchlet with the minute glumes of two spikelets from which florets Ihave: fallen i ie Us nO a aise, rr 50 . A, spikelet of Miltum effusum: B, floret... ... 2:5.) 53e 50 . A, glumes, and B, floret of Oryzopsis racemosa......... 51 . A, glumes, and B, floret.of Sizpa spariea....... ..).. ae ot ..opikelet of Aristida dichotoma.o: vans fio) 2 51 . A, spikelet of Elewsine indica; B, inflorescence......... 55 . A, spikelet of Capriola Dactylon; B, inflorescence....... 59 . A, spikelet of Chloris latisquamea; B, fertile lemma spread out; C, sterile lemma spread out; D, inflorescence.... 56 LIST OF ILLUSTRATIONS x] Fig. PaGE 50. A, spikelet of Boutelowa curtipendula; B, fertile lemma spread out; C, sterile lemma spread out; D, inflores- epee nen gc ahh rec eg ae. ek ala acu w Aisi! gosh 57 51. A, spikelet of Bouteloua gracilis; B, fertile lemma spread out; C, first sterile lemma spread out; D, second sterile lemma spread out; E, wnflorescence................ 58 52. A, fascicle of Aigopogon tenellus; B, lemma, and C, palea, spread out, of the sterile spikelet; D, lemma and HE, fadiies, OF periect spikelets. oon os. keel ow we eld ee 61 53. A, fascicle of Hilaria Belangeri; B, glumes of staminate spikelet; C, two views of the perfect spikelet; D, fertile CLYENE Soo SOI 2) See SE Bp Aas Cees ee a Tear ee 62 54. A, bur-like fascicle of Nazia aliena; B, single spikelet; Rey awit et itl ae ea Lk 63 55. A, spikelet of Anthoxanthum odoratum; B, pair of sterile florets below the perfect floret; C, perfect floret...... 64 56. A, spikelet of Phalaris canariensis; B, fertile floret with pair of small sterile florets attached at the base....... 65 ee emieelen OF rice (OTY2O SANE) coo ek oe ke ee eo 66 58. Spikelet of Homalocenchrus oryzoides............0.05. 66 59. A, pistillate spikelet, and B, staminate spikelet of Zizania ON) SUNSTRIDER PP Ee EDO 66 60. A, spikelet of Panicum miliaceum, side view; B, same seen from the back; C, sterile and fertile florets removed from the glumes, side view; D, fertile floret......... 69 61. A, two views of spikelet of Syntherisma sanguinalis; .teriae floret, iiilOrescence. 6... de ee es eae 70 62. A, two views of spikelet of Paspalum leve; B, fertile | mere Ge MN GTESGEMCe Ws ese make aia ara eueave oe 71 63. A, rachis of Paspalum leve, spikelets removed; B, rachis _ of a Paspalum with paired spikelets; C, cross-section of rachis, showing raised center and thin margins....... 71 64. A, part of a raceme of Stenotaphrum secundatum, front Pee ey as wig hota od athe wee sianla sees 72 XI LIST OF ILLUSTRATIONS Fic. PAGE 65. A, part of raceme of Axonopus furcatus; B, inflorescence: C, cross-section of rachis. :0..i5.c......... 73 66. A, spikelet of Hr-ochloa punctata; B, fertile floret. ...... 73 67. A, diagrammatic panicle; B, two branches of panicle with terminal spikelets removed................... 74 68. Small part of bristly panicle of Chetochloa Grisebachii.. 74 69. A, fascicle from panicle of Chetochloa lutescens; B, spike- like panicle Of Same os oe. kh ae ee ce re 70; Burot-Cenchrus myosuroides 2.2. 5 ie eee 76 71, Bur of Cenchrus pauciforus 3.00. 6 76 72. Base of. plant of Amphicarpon Purshit... ... . 2 ae 77 73. A, two views of single joint of raceme of Holcus halepen- sis; B, diagram of raceme of four joints; C, diagram ol. rachis and pedicels.....0.. 0.02... 22 >. ee 80 74, A, diagram of single joint of raceme of Erianthus sac- charowdes; B, three jomts of taceme.........a3eee 81 75. A, single jomt of a raceme of Andropogon scoparius; B, small part of compound mflorescence....... 222) 82 76. A, single joint of raceme of Manisuris cylindrica; B, another view of two joints; C, inner face of rachis joint and pedicel, spikelet removed; D, part of cylindrical, many-jomnted racemie.< 26s cei ne ine ce) 83 77. A, singie joint of raceme of Rytihx granularis; B, reverse view; C, diagram of rachis and pedicels of three joints of raceme, spikelets removed; D, view of inner face of first glume of sessile spikelet; E, raceme; F, reverse WIOW af ut oe ui ge ee eG oor ee 84 78. A, one-jointed raceme of Rhaphis pauciflora; B, base of raceme and summit of branch; C, the hairy summit of branch from which raceme has fallen; D, inflorescence 86 79. A, single joint of raceme of Heteropogon contortus; B, per- fect spikelet from which sterile spikelet has fallen; C, base of fertile spikelet and its callus; D, raceme; E, diagram of a raceme; F, diagram of rachis and pediedle ol four joints of raceme. . 20. 4Gen 2... ee 86 LIST OF ILLUSTRATIONS xi Fig. PAGE 80. A, two joints of pistillate part of raceme of Tripsacum dactyloides; B, spikelet removed from the joint; C, rachis joint from which the spikelet has been removed; D, inflorescence; E, diagram of rachis of pistillate part; fs pair oF stam ate spikelets... oe... el ek 81. A, part of a cross section of an ear of corn, Zea Mays, showing two pistillate spikelets standing at right angles to their axis (the cob); B, pistillate spikelet about flowering time; C, part of raceme of staminate spikelets 82. A, pistillate inflorescence of Bulbtls dactyloides; B, pis- tillate spikelet cut from the rachis; ©, pistillate floret; D, diagram of half a head, showing one of the two rows of spikelets; E, staminate inflorescence; F, staminate Pu AR ee ee ge yarn a PM gai ata oes 83. Diagram of inflorescence of Festucee................. 84. Diagram of inflorescence of Hordex.................. 85. Diagram of inflorescence of Avenee.................. 86. Diagram of inflorescence of Agrostidee............... 87. Diagram of inflorescence of Chloridee................ 88. Diagram of inflorescence of Naziew.................. 89. Diagram of inflorescence of Phalaridee............... 90. Diagram of inflorescence of Oryzee.................. 91. Diagram of inflorescence of Zizaniee.................. 92. Diagram of inflorescence of Panicee.................. 93. Diagram of inflorescence of Andropogonee............ 94, Diagram of inflorescence of Tripsacee................ 89 on FIRST BOOK OF GRASSES FIRST BOOK OF GRASSES INTRODUCTION THE purpose of this primer is to give those with little or no knowledge of botany such an understand- ing of the structure of grasses as will enable them to use manuals of botany and other technical works, to the end that our native grasses may become better known and their worth and beauty be more fully appreciated. The best method of studying any organisms is to observe and examine the organisms themselves. Since these can not be provided in a book, drawings of the objects studied are here offered as the best substitute. These drawings are purposely somewhat diagrammatic in order to bring out particular char- acters that may be less prominent in the actual plants. While the drawings convey clearer ideas of structure than can words and are to be used con- - stantly with the text, they can but inadequately take the place of the plants themselves. The student, therefore, should collect for study as many different kinds of living grasses as possible. | The idea of a primer has been kept in mind. The subject is presented as simply as possible, and only enough grasses are examined in each lesson to illus- if 2 FIRST BOOK OF GRASSES trate the different modifications and to prepare the student to comprehend the greater modifications shown in subsequent lessons. The classification of grasses, that is, the grouping together of related forms, is based on the characters of the aggregate of minute flowers and bracts known as the spikelet. It is necessary, therefore, for anyone who wishes to be able to identify a given grass to understand the structure and modifications of the spikelet. This primer is really an elementary study of the morphology of the spikelet. [Morphology is a branch of science that treats of form and structure. The study of the morphology of the spikelet enables one to recognize its various organs under whatever form they may assume.| USE OF TECHNICAL TERMS Many persons who might otherwise make an effort to learn something about our common wild flowers and trees, as well as grasses, are deterred — by the sight of the unfamiliar words used in botanical descriptions. This supposed lion in the way, if one will but draw near enough to see, is only a ‘“‘ harmless necessary cat.’”’ No boy learns a trade, no girl learns to sew without learning the names of the tools used. Words like hames, whippletree, terrets, and a hundred more, meaningless to the city-bred rider on a trolley-car, are familiar terms to the farmer.! Such 1Mark Twain’s description (in ‘A Tramp Abroad ”’’) of how they hitch horses in Europe is a good example of the con- INTRODUCTION 3 terms as carburetor, accelerator, clutch, spark-plug or magneto, unknown a few years ago, are now understood by nearly everyone, and those who do not as yet understand these terms are by no means deterred thereby from buying (or wishing for) an automobile. Spikelet, glume, and lemma are words no more difficult to learn than are hames, crupper, or whippletree, carburetor, clutch, or magneto. The reason for using these botanical terms is the same as that for using the names of the different parts of a harness; they are simpler and more exact than would be a descriptive phrase. It is simpler to say -“‘terrets’’ than to say ‘‘the rings that stick up in the middle of the harness on the horse’s back that you pass the reins through” and it is simpler to say fusion caused by want of technical terms: ‘‘The man stands up the horses on each side of the thing that projects from the front end of the wagon, throws the gear on top of the horses, and passes the thing that goes forward through a ring, and hauls it aft, and passes the other thing through the other ring and hauls it aft on the other side of the other horse, opposite to the first one, after crossing them and bringing the loose end back, and then buckles the other thing underneath the horse, and - takes another thing and wraps it around the thing I spoke of before, and puts another thing over each horse’s head, and puts the iron thing in his mouth, and brings the ends of these things aft over his back, after buckling another one around under his neck, and hitching another thing on a thing that goes over his | shoulders, and then takes the slack of the thing which I men- tioned a while ago and fetches it aft and makes it fast to the thing that pulls the wagon, og hands the other things up to the driver.” 4 FIRST BOOK OF GRASSES ‘‘slume”’ when speaking of that organ of a grass than to say ‘‘the little green scale on the outside of the thing with the seed in it.’’ In the first lesson nearly all the new words that a study of grasses will require are explained and illus- trated by figures. The few additional terms neces- sary are explained as they are used. No attempt is made to write a primer of grasses in words of one syllable nor to produce a work on ‘‘how to know the grasses’’ without mental effort. It can not be done. USE OF LATIN NAMES Besides unfamiliar terms there are the unfamiliar Latin names of the plants which some hesitate to encounter. But many of the names in common use for trees and herbs are the botanical names. Mag- nolia, Rhododendron, Petunia, Asparagus, Chrysan- themum, Phlox are the Latin botanical names and are freely used by all without hesitation. Panicum, Paspalum, Bromus, Festuca, Hordeum are no more difficult. As in the case of such terms as glume and lemma, the Latin names of plants are used for the sake of exactness. Common names of plants, espe- cially of those which are useful, troublesome, or conspicuous, are more definitely applied in older countries where the inhabitants have dwelt in a region for many generations than they are with us. Our ancestors brought names of old world plants with them to their new homes and applied them to INTRODUCTION 5 plants something like the familiar ones. Conse- quently, many common names are used in different parts of the country for widely different plants. In Illinois ‘‘June-grass’”’ is Kentucky blue-grass (Poa pratensis), a valuable pasture grass; in Maine ‘‘ June- grass’? is Danthonia spicata, an almost worthless little relative of wild oats; and in parts of the West it is Keleria cristata. The name “‘blue-joint”’ is used for three very unlike grasses. On the other hand, many plants have different names in separate parts of the country. Around Washington, D. C., for example, Azalea is commonly called ‘‘honey- suckle.” Many economic plants (such as potato, turnip, and rye) have common names uniform in any one language but different in distinct languages. When the Latin name of a plant is used, it is definitely understood not only throughout the United States but throughout the world what species is referred to. However, the primary reason for using the botanical names is that these indicate the relation- ship of the plants. All plants of a kind have the same genus (or generic) name. [Genus is the sin- cular, genera the plural, generic the adjective.| Kentucky blue-grass and all its kind are Poa: P. pratensis, P. trivialis, P. annua, P. Sandbergti, and so on. The common names of these, Kentucky blue-grass or June-grass, rough meadow-grass, spear- grass, little bunch-grass, respectively, give no clue to their relationship or kind. Knowing Poa pratensis anyone hearing of any grass named Poa has an idea 6 FIRST BOOK OF GRASSES of what it is like; it is something like Poa pratensis. Some common names, especially those of trees, indicate the kind: Oak, with black, white, scarlet, swamp, and post oak, for example, and also hickory and ash; but for herbs, and especially grasses, the common name usually gives no indication of the kind of plant it refers to. Often the name is mis- leading. Rib-grass is not a grass, but a plantain; poison ivy is not an ivy, but a sumach. To convey definite ideas we must use definite terms and definite names. 7 7 TOOLS NEEDED Any work that one engages in requires tools. For the study of grasses we need but few. Grass flowers are too small to be seen distinctly with the naked | eye. A lens magnifying about ten diameters is necessary. This may be mounted on a stand or it may be a hand lens. A simple dissecting microscope with two or three lenses of different magnification — would be more convenient and would well repay the cost, but it is not absolutely necessary. If one has only a hand lens, an eye-piece, such as watchmakers place in the eye, will also be found very useful in dis- secting, as 1t leaves both hands free. One or two dissecting needles are needed. ‘These can be made by forcing the heads of coarse sewing needles into a pencil-shaped piece of soft wood. After some prac- tice one learns to use the nail of the left forefinger skilfully in dissecting. One can work more rapidly INTRODUCTION 7 with this and one needle than with a pair of needles. A scalpel is useful, but the small sharp blade of a penknife will answer instead. It is well to have a piece of black paper or cardboard on which to place hairy spikelets. The hairs on the different parts show up well against this background. It is the aim to use, so far as possible, the charac- ters that may be seen in the different parts of the spikelet with but little dissection. When further dis- section 1s necessary, instructions will be given at the end of the lesson requiring it. LESSON I THE GRASS FAMILY To most persons grass 1s almost any green vegeta- tion of rather low growth, especially such as may be grazed. To the student of plants, a grass is a member of the natural family Poacez, or Graminee, distinguished by its structure. Grasses are herbs with round or flattened (never 3-angled), usually hollow stems (culms) solid at the joints (nodes), and 2-ranked, alternate, parallel- veined leaves, composed of two parts, the sheath, which surrounds the culm like a tube split down one side, and the blade, which is usually strap-shaped, flat, folded, or with rolled margins. At the junction of the sheath and blade, on the inside, is a small appendage (the ligule); this 1s commonly thin in | texture; sometimes it is only a ring of hairs, rarely it is obsolete. The plants may be annual or peren- nial. The root, stem, and leaves are the vegetative part of the plant (Fig. 1). These are all that are concerned with the life of the individual plant. The flowers have to do with perpetuating the species. In grasses the vegetative parts are more uniform and characteristic than in most other families. Having stem and leaves of any plant, it can always be readily decided whether or not it is a grass. The 8 THE GRASS FAMILY 9 we xo P/ISTILSS> ; EI i er SS ty By . a as STAMENSS<— = ae SS Fic. 2. Typical complete flower, showing calyx, corolla, stamens and pistils. f only plants that may rea- Y sonably be mistaken for grasses are the sedges. In these the culms are solid or pithy, are not jointed, and are commonly 3-sided; the leaves are always 3-ranked, and the sheaths always closed. The flowers of grasses are small and inconspicuous. They consist of a single pistil with a 1-celled, 1-ovuled ovary, two styles, each with a feath- — ery stigma, and three (rarely one or six) stamens with deli- eate filaments and 2-celled anthers. ‘T'wo minute scales, called lodicules, situated back Fig. 1. Vegetative part of a of the pistil, at blooming time grass plant; part of leaf become turgid and force open opened out. : the enveloping scales. In Fig. 2 are shown the parts of a common flower 10 FIRST BOOK OF GRASSES (the wild prairie rose with long styles). The calyx and corolla are the floral envelopes; the stamens and pistils are the essential organs of a flower, the parts that produce seed. ‘The floral envelopes protect the essential organs in the bud and, by secreting nectar which attracts insects or in other ways, com- monly aid in securing the fertilization of the flower. The pistil consists of the ovary, style, and stigma. / ‘The ovary contains the Ww’ ovules, which when fer- tilized develop into the seeds. The style serves to lift the stigma into the air. The stigma is more or less expanded, has a ; viscid surface to which Fig. 3. Grass flower, showing sta- the pollen-grains adhere mong and, Dit! and the md and upon which they ger- minate, sending their con- tents in a minute tube which pushes down through the style to the ovules, fertilizing them. The grass flower (Fig. 3) is reduced to the essential organs, the floral envelopes being represented by the minute lodicules. Each flower is borne in the axil of a small green bract (the lemma) and is subtended and enveloped in a second bract (the palea). The flower with its lemma and palea is termed the floret (Fig. 4). The ripened ovary (the grain, or caryopsis) (Fig. 5) consists of a small embryo lying at the base THE GRASS FAMILY 11 of a mass of starchy endosperm. [Endosperm means within the sperm or seed. It is the store of food used by the infant plantlet when it begins to grow.| The ‘‘germ”’ of a kernel of corn is the embryo, while the remainder of the kernel au. is starchy endosperm. The grain //| // lies in the palea with the hilum .|\|\\_, (the scar of the point of attach- ‘ ment) toward it, and the embryo \W/ on the side toward the lemma. °°” W Fig. 5 gives two views of a grain, +4 one showing the hilum, the other the embryo. In Fig. 81, A (page 91), are two ker- nels of corn showing the embryos. The grain with very few exceptions is permanently in- \ closed in the lemma and palea, the ma- ' evoosrane | ture floret being the fruit, that is, the ‘: — ii/ ~=— seed with its permanent envelopes. The \Qy,,.,, florets are borne in two ranks and alter- nate upon an axis (the rachilla). Below them are two bracts without flowers (the glumes). The glumes, rachilla, and florets together form the spikelet. _ : Fig. 6 is a diagram of a branch with Fic. 5. Two leaves and flowers arranged as are the i of a glumes, lemmas, paleas, and flowers of a grass spikelet. Fig. 7 is a diagram of a spikelet for comparison with Fig. 6. [The hy- pothetical flower-bearing branchlet is never elongate, ret at flow- ering time. 12 FIRST BOOK OF GRASSES as here shown for the sake of comparison. The palea is immediately above the lemma and the flower immediately above the palea.| It will be seen that the spikelet is theoretically a leafy flowering branch with a jointed main axis, the flowers, except “RACHILLA Fie. 6. nee of a flowering Fic. 7. Diagram of a grass - branch. spikelet. for the minute lodicules, reduced to the essential organs. In Fig. 8 a typical grass spikelet is shown, the lemmas and paleas nearly closed together and concealing the flowers. The spikelet is characteristic of grasses and is not — found in any other family except that of the sedges. GLUME eo Le 2 ae eae eS ae THE GRASS FAMILY 13 In the spikelets of sedges the florets are commonly, but not always, spirally arranged, there never is a palea, and the fruit is an achene or nutlet. [The ‘“‘seeds”’ of buttercups and mints are achenes or nut- lets. | In grasses specialization takes place mostly in the spikelet. By its vegetative characters we know a given plant to be a grass, but it is by its spikelets and their arrangement that we know what kind of a grass it is. The genera of grasses and the groups of genera called tribes are based on the structure of the spikelets and their arrangement in the inflorescence. Before studying the spike- let we must observe the relatively few specializations of the vegetative parts. _ As in other plants, stems or parts of stems may be underground. ‘These underground stems (rhizomes, or rootstocks) are borne at the base of the main culm under the earth, spread out horizontally, and in due time send up shoots which form young plants at a distance from the parent. Sod-forming grasses have this. kind of underground stem. Kentucky blue- Fic. 8. Generalized spikelet. 14 - FIRST BOOK OF GRASSES grass (Poa pratensis, Fig. 9) furnishes an excellent example. Sometimes the rhizome is thick and woody, sending up shoots from its nodes, the whole forming a dense colony, as in gama-grass (T’ripsacum dacty- loides). A rhizome, being a stem, is jointed and bears scales, which are reduced leaves. By these it may always be distinguished from a root, which is not jomted and never bears scales. In some grasses the shoots borne at the base of the culm are on the surface of the earth instead of beneath it. Such shoots are _ stolons, or run-— ners. These, like rhizomes, are Fig. 9. Base of plant and underground parts, jointed and bear roots and rhizomes, of Poa pratensis. scales or, some-— times, well-developed leaves. Rhizomes and stolons both bear roots at the under side of the nodes. Ina few species, Bermuda-grass for one, a plant may produce either rhizomes or stolons according to the conditions under which it is growing. There is no real difference between a rhizome and a stolon, the one is below ground and colorless, the other above ground and green. Culms are hollow in most grasses, but in corn, sugar-cane, sorghum, and related grasses they are THE GRASS FAMILY 15 pithy. They may be erect, spreading, or creeping; they may be simple or freely branching. A branch is borne only at a node in the axil of a sheath, that is, between the sheath and the culm. It either grows up parallel with the parent culm until it emerges from the sheath or the young branch splits the sheath and grows outward. In manuals of botany these two methods of branching are called intravaginal, that is, inside the vagina (Latin for sheath), and ex- travaginal, outside the sheath. In bunch-grasses, like orchard-grass and the wheat-grasses of the West, the branching is intravaginal; in Kentucky blue-grass, quack-grass, and others producing rhi- zomes or stolons, the branching is extravaginal. The branches borne at the middle and upper nodes of a culm are nearly always intravaginal. If they spread from the parent culm they do not burst through the sheath but carry it with them. Leaves are always borne at the nodes and are always 2-ranked (see Fig. 1, page 9). In corn and other large grasses the leaves sometimes appear to be all on one side instead of 2-ranked. This is due to a twisting of the culm inside the sheath. ‘Sometimes in large grasses, particularly in sugar- cane and in bamboos, the leaves fall, leaving the culm naked. In relatively few grasses the edges of the sheath are grown together, forming a tube. Some- times the blade of the leaf is not developed. This is always the case in the leaves or scales of rhizomes (Fig. 9), and often in those of stolons and in the 16 FIRST BOOK OF GRASSES lowermost leaves of a culm, especially in bamboos. Blades may be flat or folded (often called con- duplicate) or involute; that is, rolled lengthwise. Rarely the inrolled edges are grown together, so that the blade really has no upper surface. Such leaves are called terete (meaning rounded). Blades vary greatly in size, shape, and texture, smoothness or hairiness. In broad leaves there is sometimes a narrow neck, or petiole (leaf-stalk), between the sheath and the blade. SUMMARY Grasses are distinguished by jointed, round or flattened, usually hollow, culms, with solid nodes; 2-ranked leaves, composed of sheath and _ blade, with a ligule at their junction; and by the spikelets with 2-ranked glumes and florets. REVIEW (1) How is a grass distinguished from all other plants? (2) Break a cornstalk and note the arrangement of the torn fibers standing out of the pith. Compare this with the cut end of any twig of a tree or shrub. Cut across a wheat, oat, or rye straw and compare with the cornstalk and with the twig. (3) Examine the culm (nodes and internodes) above and below ground and leaves (sheath, ligule, and blade) of any available gTAass. ae (4) How is a rhizome distinguished from a root? (5) What is the difference between a rhizome and a stolon? LESSON II THE SPIKELET AND THE INFLORESCENCE THEORETICALLY the spikelet is a reduced leafy branch. In the generalized spikelet shown in Fig. 8 the likeness to a jointed culm with 2-ranked leaves (Fig. 1) is readily seen, the glumes and lemmas corre- sponding to sheaths, their blades not developed. The palea, with two nerves and with its back to the axis, corresponds to a minute bract (the prophyllum) borne at the base of a branch in the axil of a sheath. The prophyllum is always 2-nerved, with its back (that is, the space between the nerves) against the main axis and its margins clasping the young branch. The flower, also, is theoretically an ultimate branch- let. In the flower-bearing lemmas, therefore, the palea is developed, while in the glumes, bearing no flowers, there are no paleas. Glumes and lemmas are, morphologically, reduced leaves, the lower pair, not flower-bearing, being termed glumes, the flower- bearing ones being termed lemmas. (See Fig. 7.) The jointed axis of the spikelet (the rachilla) corresponds to the jointed culm and, like it, usually breaks at the nodes, the internode (the part of the rachilla between two nodes) remaining attached to the floret at its base (Fig. 4), just as in a broken grass stem the internode of the culm remains with 17 18 FIRST BOOK OF GRASSES the sheath that surrounds it; that is, the break normally comes just under the node. Rachis (which means the spine, or backbone) and axis (the imaginary central line of any body) are often used inter- / Y* \\ /\ | changeably as bo- WY Yr) | tanical terms. In | if most recent works i ig LAA on grasses and in [Oo (SSN I) thee Ieee %, iy Ca aX wy Ar ese lessons, aX1S a a Yi Pe N\\ | Hi is used for the : vy ye iv 1 | main axis of acom- YY f@ i LP We ] pound inflores- : / Db | ie Ny cence, rachis for | 7 i ay 4 iy the axis or sup- lV | Ni port of the spike- } y Wy ) lets. In Fig. 10 : y are shown the axis | of a panicle (A). Le a a and the rachis of Fic. 10. Forms of inflorescence: A, panicle; & raceme (B); the en receae, te See rachis of the spike (C) is concealed by the overlapping spikelets. Spikelets are borne pediceled (that is, on a pedicel or foot stalk) or sessile (without a pedicel) in leafless panicles, racemes, or spikes (Fig. 10). These different types of inflorescence insensibly grade into each other. The axis and branches of a panicle and the rachis of a raceme or spike may be as elaborately modified and specialized as may be the parts of a THE SPIKELET AND THE INFLORESCENCE 19 spikelet. The axis, rachis, or branches may be . continuous (not jointed), or articulate (jointed) and usually disarticulating (breaking up). The break- _ ing up takes place at definite points and has to do with scattering the seed. The point of disarticula- tion is the same in grasses of the same kind (or genus) and is usually alike in related. genera, and for this reason is of great importance in the classifica- tion of grasses. When there are no joints in the axis or branches, the disarticulation comes in the spikelet, either above the glumes and between the florets or below the glumes. Modifications of these two ways of disarticulating will be met with later. The study of the form of inflorescence and the modification of its parts will be carried on together with that of the spikelet. SUMMARY A spikelet consists of glumes and florets, in two ranks and alternate on the rachilla, the florets consist- ing of lemma, palea, and the inclosed flower. Every organ found in the most highly specialized spikelet is to be interpreted as an elaboration or a reduction — of one of these parts. The spikelet is the unit of the inflorescence; the floret is the unit of the spikelet. The spikelet is always simple; that is, the rachilla never branches. The floret is always 1-flowered with never more than one lemma and one palea; the glumes and florets are always alternate, two consecu- tive ones never being borne one above the other. 20 FIRST BOOK OF GRASSES These basic facts kept in mind will aid in the recogni- tion of complicated or congested spikelets and in the correct interpretation of their parts. REVIEW (1) Examine a spikelet of a brome-grass, such as cheat or chess. Separate the florets from each other and from the glumes. Note that these disjoint without tearing. Open out the lemma and palea. Note that these permanently adhere at their base; that they can only be torn or cut apart. (2) Name the parts of a spikelet. (3) What is their arrangement? (4) What is the difference between a rachis and a rachilla? LESSON III MODIFICATIONS OF THE SPIKELET TakINnG the generalized spikelet as a beginning, examine Figs. 4 and 8. Note that the glumes and lemmas have nerves or veins (fibro-vascular bundles) running from the base to the apex or nearly to it, one nerve in the middle and an equal number on each side, there being an odd number of nerves in the glumes and lemmas. In the palea there are only two nerves; none in the middle. The modifications _and variations of spikelets will be studied, as nearly as possible, in the order of their increasing com- plexity. No attempt should be made to fix in mind the forms of specialization here enumerated. ‘This lesson is only meant to put one on the lookout for modifications, so that one may be prepared to recog- nize a given organ under various guises. (1) Spikelets differ in size. (Bromus or brome- grass, meadow fescue, and blue-grass are examples.) _ (2) The number of florets may be reduced to one or increased to twenty or more. (3) The parts of the spikelet vary in their relative sizes. The glumes may be large and the florets small or the florets large and the glumes small. (4) The rachilla joints may be slender or thick, so short that the florets appear to be opposite, or nearly 21 22 FIRST BOOK OF GRASSES as long as the florets themselves; the node at the base of the floret (the callus) is sometimes prolonged into a sharp point; the uppermost rachilla joint may bear no floret and may extend into a little bristle. (5) The glumes may vary in shape, in texture, and in the number of their nerves and may be gla- brous (smooth) or pubescent (hairy) ; sometimes they are reduced to rudiments and sometimes they are suppressed. (6) The lemma is subject to such great modifica- tions that we shall now note only the simplest ones. As in the glumes, the shape and texture and the number of nerves vary. The summit of the lemma may be acute (pointed) or acuminate (long-pointed) or obtuse (blunt) or it may be lobed or cleft. The nerves may be faint or strong, or may extend into awns (bristles) beyond the body of the lemma. The lemma is sometimes minute, but it is never sup- pressed. (7) The palea is always 2-nerved, but in a few grasses the nerves are so close together as to appear like a single one. In others they are far apart and the palea may split between them. The palea differs in size and texture. In a few genera it is reduced or even suppressed. (8) Spikelets are compressed (flattened) lated (sidewise), as in Figs. 11-14, or dorsally (on the back), as in Figs. 60-66. The side or back of a spikelet is recognized from the position of the florets on the rachilla. The palea side of the floret is always MODIFICATIONS OF THE SPIKELET 23 toward the rachilla. Taking this as the ‘‘front”’ of a floret, the back (or dorsum) is the back of the lemma. Spikelets with many florets, or those in which the glumes or lemmas are folded on the mid- nerve, are generally laterally compressed ; those with a single fertile floret and with convex (rounded) glumes and lemma are generally dorsally compressed. (9) Spikelets are sometimes unisexual (of one sex) instead of perfect (having both stamens and pistil). The two kinds, pistillate (the ovule-producing) and staminate (pollen-producing) may be borne on a single plant, as in corn, with pistillate spikelets in the ear and staminate spikelets in the tassel, or in differ- ent plants, as in salt-grass and buffalo-grass. Grasses with staminate and pistillate spikelets on the same plants are moncecious (which means dwelling in one house); those with staminate and pistillate spikelets on different plants are dicecious (dwelling in two houses). The unisexual spikelets of a single species may be similar in appearance, or they may be very unlike, as in corn. (10) Some grasses with perfect spikelets bear in _ addition staminate spikelets or neuter spikelets (hav- ing neither stamens nor pistils). These additional spikelets may be similar in appearance to the perfect ones or very unlike them. They are borne in the same inflorescence as the perfect spikelets and are © usually paired with them. (11) The florets of a single spikelet may be of two kinds, perfect and sterile, the sterile being either 24. FIRST BOOK OF GRASSES staminate or neuter. In spikelets like those of Figs. 11-14, with several to many florets, the uppermost florets are commonly sterile (not perfecting seed), though they are like the fertile florets in appearance and have rudimentary stamens and pistils. In some grasses the sterile florets are very different from the fertile ones and may be borne above or below them on the rachilla. The position of sterile florets in the spikelet is the same in large series of related grasses; hence it is of great importance in classifying genera. The type of modification of the sterile floret is also uniform within a genus, and generally in related genera. It commonly consists of a lemma without a palea, but there may be a rudimentary or even a well-developed palea. These types of modification will be brought out and illustrated in the succeeding lessons. } SUMMARY All spikelets are built on the simple plan of 2- ranked florets with a pair of glumes at the base. The spikelet as a whole and each of its organs is subject to modification. The palea and one or both glumes may be suppressed; the lemma may be re- duced but is never suppressed. The position and type of modification of sterile florets are of impor- tance in classification. The parts of a spikelet, however complex, are recognizable as rachilla, glumes, lemma, or palea. LESSON IV PEDICELED SPIKELETS OF FEW TO MANY FLORETS Taxine the spikelet of cheat or chess (Bromus secalinus), Fig. 11, as a starting point, we have one but little different from the : diagrammatic spikelet (Fig. 8). [Names incidentally mentioned should not be memorized.] The lemmas are convex on the back, several-nerved, 2-toothed at the © apex and bear an awn from be- tween the teeth. The awn is the midnerve extending beyond the body of the lemma. The rachilla joints are short, bring- ing the florets (Fig. 11, B) close together. The articulation is ! above the glumes and between F's. 11. A, several-flow- : ered spikelet of Bromus the florets. The palea is grown secalinus; B, single fast to the grain. All species-of %7 — Bromus have spikelets of this character, differing in size, texture, length of the awn, which may be much longer or reduced to a mucro (a minute point) or even suppressed, in being glabrous, as in cheat, or pubescent. The pubescence may cover the lemma 25 26 FIRST BOOK OF GRASSES or be along the margins only. These differences distinguish the species. A genus is composed of one to many species having few to several important characters in common, and presumably descended from a common ancestor. Groups of species having less important characters in common form related genera. Festuca (Fig. 12) is related to Bromus, having few to several-flowered spikelets, disarticulating above the glumes and between the florets and with several-nerved lemmas; but the lemmas are awned from the tip, or pointed only, and not toothed, and the palea is not grown to the grain. A large number of grasses have laterally compressed spikelets of this general type, Fie. 12. A, spikelet of ae disarticulating above the tuca ovina; B, lemma de- glumes and between the few hanes to many florets. They are sorted into genera and the genera separated from each other chiefly according to the modifications of the lemma. In Panicularia (Fig. 13) the lemmas are broad and obtuse with strong parallel nerves. In Poa (Fig. 14) the lemmas are keeled on the back and have five nerves converging toward the acute but never awned apex. The species figured (Ken- _tucky blue-grass, Poa pratensis) and many others ee ee a nig Brac PEDICELED SPIKELETS ah are villous (having soft curly hairs) on the lower part of the midnerve and the marginal nerves and have a tuft of white cottony hairs at the base, but this pubescence is not found in all the species. In all the grasses mentioned so far, the spikelets are borne in panicles (see Fig. 10, A). Spikelets much like those of Panicularia (Fig. 13) but borne in a raceme and having awned lemmas are found in Pleuropogon (shown in Fie, 10, B). In these spikelets the palea is crested or winged on the nerves 7 (Fig. 15, showing a three quar- Fic. 14. Spike- ter view of a palea removed (0 0% ow from the floret). Returning to Fig. 11, A, we ae note the midnerve of the lemma Panicularia extending as an awn beyond the sepenire- minutely toothed apex. The mid- nerve and the two lateral nerves as well are extended into awns in T'riodia flava (Fig. 16, the floret seen from the back); —_' the apex of the lemma is toothed and the {%*.,?, nerves are villous below. In Fig. 17 (floret Pleuropogon of Cotiea pappophoroides opened out and Mahi oe) seen from the back) the lemma is lobed and nine to eleven of its many nerves are extended into awns. 28 FIRST BOOK OF GRASSES After the foregoing the spikelet and its parts will be recognized in most of the genera of the group having few to many-flow- ered pediceled spikelets. As stated in Lesson III the florets in a single spike- \ t let may be of two kinds. ‘jw The simplest spikelet of Nf f| 4 Za cog ; this type is found in the Floret of reed (Phragmites commu- es nis). In this, the lowest floret is staminate or neu- Fic. 17. Lemma of ter and its lemma is much longer 0% 2*PPophorotdes. than in the other florets (Fig. 18, A). In the per- fect floret (Fig. 18, B) it will be seen that the palea = ees ao as ZzZ mee. << Ss Sy pe ps ACA, ae SSS YA Ss is very much shorter than the lemma, that the © Fig. 18. A, spikelet of Phragmites communis; B, floret. rachilla bears copious long soft hairs, and that in- stead of disarticulating at its summit and remaining PEDICELED SPIKELETS 29 attached to the floret next below, it disarticulates at its base, remaining as a tiny feathery stem to the floret next above, its copious long hairs carrying the floret before the wind, dispersing the seed. [The hairs are much more co- \\Vii\\ 4 pious than shown in the figure; they \\ NY Up: are slighted to avoid obscuring the difference in the florets. | Another spikelet with two kinds of florets is shown in Fig. 19 (Melica mutica). In this the lemmas of the Fic. 19. Spikelet of : : Melica mutica. upper florets are reduced in size, changed in shape, and contain no flower. Two or three of them are crowded together in a little club- shaped body. In the species figured, this modifica- tion is more marked than in most of the ae In Fig. 20 is shown a side view of the florets of a spikelet of Pappophorum vagina- tum, the glumes re- moved. The lowest floret is perfect. Its broad lemma is cut into many spreading awns (compare with Fig. 17). The two to four other Fie. 20. Florets of Pappophorum florets are crowded on se agen the very short rachilla and are sterile; their lemmas are similar to that of the one fertile floret. The ria CNS 30 FIRST BOOK OF GRASSES rachilla does not disarticulate, the sterile florets re- maining permanently attached to the fertile one, the numerous awns of all together forming a pappus-like crown which carries the seed before the wind. |Pap- pus is the ‘‘down”’ on the seed of a dandelion, thistle, or other plant of their family.] Next we shall-examine the inflorescence of a grass having spikelets entirely of sterile florets in addition to spikelets of fer-_ tile florets. Ex- f\) amine Fig. 21, A “a (Cynosurus crista- ‘ea tus), which shows (ti yf a small part of a 4? spike-like panicle. The spikelets are borne on minute Fic. 21. A, part of a panicle of Cynosurus pedicels on Very cristatus; B, sterile spikelet; C, fertile § h ort compound REN branches. The lower one to three spikelets of each little branch are sterile, the lemmas containing no flowers (Fig. 21, B). The upper one to three spikelets are smaller and fertile (Fig. 21, C). When the bracts of the sterile spikelet are all alike empty, why are all but the lower pair called lemmas, instead of glumes? In many cases the nature of modified organs can only be recognized by their correspondence to or- gans in the same relative position in allied but more simple forms. In all the spikelets examined PEDICELED SPIKELETS 31 so far (and in all but a very small number of grasses) the bracts above the lower pair are flower- bearing or have a palea, which indicates their struc- tural identity. Corresponding parts in a modified spikelet are, therefore, regarded as lemmas. In the grass just examined the sterile spikelets remain on the panicle branches after the fall of the ripened fertile florets from their glumes. In Fig. 22, A (Achyrodes aureum), is showna fascicle 7R of one fertile and three }} sterile spikelets of another grass. In this the fascicles hang from the short slen- der branches of a narrow panicle and disarticulate from them, falling entire. This is the first example we have had so far of disartic- ulating branches of the in- florescence. In the figure the fascicle is seen from the Fig. 22. A, fascicle of three sterile inner face to show the fer- pee ee ea sara a tile spikelet, which from _ spikelet. | the outside is nearly hid- den by the sterile ones. Fig. 22, B, shows a sepa- rate fertile spikelet. It will be seen that except © for the glumes, the two forms are strikingly dif- ferent. The fertile spikelet is reduced to one fertile and one rudimentary floret, both awned, 32 FIRST BOOK OF GRASSES while the sterile spikelets are many-flowered and awnless. We shall next examine a grass having unisexual spikelets (see Lesson III, page 23), the two forms borne on different plants (dicecious). , (In the group with relatively simple Y¥| spikelets which we are now studying ~ iA there are no monoecious grasses). “i In Fig. 23 are shown the pistillate 4 and staminate spikelets of salt-grass y] (Distichlis spicata). They differ but 6) little in appearance and are both NY, Fic. 238. Pistillate and _— staminate spikelets of Dvis- tichlis spicata. borne in narrow panicles. [¢ sig- nifies female, & male. These signs are commonly used to indicate pistillate and sta- minate plants, respectively. | In Fig. 24 are seen the strikingly Fig. 24. Staminate and pistillate spikelets of diverse staminate Scleropogon brevifolius. and pistillate spikelets of another dicecious species PEDICELED SPIKELETS 33 (Scleropogon brevifolius). The lemmas of the stam- inate spikelet are merely pointed; those of the pistillate spikelet bear three long slender twisted spreading awns. The pistillate florets fall from the glumes as a whole (the rachilla not disarticulating between them) and roll before the wind as tiny tumble weeds. SUMMARY The inflorescence and the two to several-flowered spikelets of the brome-grasses, blue-grasses and their relatives are comparatively simple. In a few genera sterile spikelets are developed and in a few others the spikelets are unisexual. REVIEW Collect specimens of orchard-grass, meadow fescue, any species of brome-grass, or of Poa, or of any available grasses having laterally compressed, few to several-flowered spikelets. Identify the different parts of the spikelets. Lemmas may be spread out for examination by cutting off the very base with a sharp knife or scalpel. Spikelets of tough or rigid texture if soaked in water for a few minutes may be dissected without tearing. If very tough or hard, boiling the spikelets in water with a little glycerine (a drop of glycerine to about a teaspoonful of water) will make them manageable and keep them from drying out during dissection. LESSON V SHSSILE SPIKELETS IN TWO-SIDED SPIKES RETURNING A Fig. 25. A, part of a spike of Agropy- ron repens; B, part of rachis seen from the edge, all but two spikelets re- moved. again to the spikelet of Bromus secalinus (Fig. 11), we shall strike out in another direction. Differ- entiation among living beings does not follow a line, but radiates like waves following the falling of a peb- ble in the water, or rather like waves of sound, in all directions. Hence we can not follow an unbroken line in studying the increasing complexity of the inflorescence of grasses. We © can only return to the center and start out on another line. Compare Fig. 10, A and B, with C, and with Fig. 25 (couch-grass or quack-grass, Agropyron repens). A raceme is a panicle reduced to its lowest terms. Eliminating the pedicels of the spike- lets of a raceme we have a spike, the spikelets set directly upon the rachis. In such an inflorescence the rachis is usually more or less thickened. In Fig. 25, A, part of a spike is shown from the flat side of the spikelet. The rachis is jointed and a spikelet is 34 SESSILE SPIKELETS IN TWO-SIDED SPIKES 35 borne at each joint, alternating on opposite sides. The rachis is thickened and the joints slightly hol- lowed on alternate sides. (See Fig. 25, B, a diagram- matic illustration of the rachis seen from the edge with all but two spikelets removed.) The spikelet is not very different from that of Bromus (Fig. 11) and as in that, the ripened 3 | florets fall from the , J i glumes. In the group of grasses taken up in this lesson the specialization is mostly in the rachis and in the position of the relatively simple spikelets. In Fig. 26, a spikelet of cultivated wheat (Triticum estivum), we have the same type of spikelet as in Fig. 25 but with fewer and much plumper florets, with broader lemmas slightly toothed at the apex, and with long awns that are scabrous (rough, like a file). [Awns form the “‘beard”’ of wheat.] The spikelets are borne on a jointed rachis as in Fig. 25 (Agropyron repens) but the joints are | shorter, bringing the spikelets closer together and hiding the rachis. In this, cultivated wheat, the florets do not readily fall from the glumes but re- ‘ \ Y WAVE 7 NA 7 W/ Y LS ie Fic. 26. Spikelet of Triticum estivum. 36 FIRST BOOK OF GRASSES main in the spike and the ripened grain is thrashed from them. This persistence of the lemma and palea has been fixed by selection in cultivation. In the closely related emmer (Triticum dicoccum) the rachis breaks at the jomts, each joint remaining attached to its spikelet. Compare Fig. 27 (Lolium multi- florum) with Fig. 25. Note that in Fig. 25 the spikelets are borne flat side against the rachis, while in Fig. 27 they stand with their edges against the rachis. The rachis itself is of the same type as that in Fig. 25. The diagram- seen edgewise (Fig. 25, B) is shown from the same position as is Fig. 27. In this, as in Agropyron, the ulating) and the florets fall. If we separate a spikelet from the rachis we find that the first glume (the one that would be against the rachis) is sup- pressed, the first floret lying directly against the rachis. In the single spikelet borne at the summit of the rachis the first glume is developed and is about as large as the second. When but one glume is present, we know which glume it is and which is suppressed by the position of the first floret, which Fic. 27. Part of a spike of Lolium multifiorum. » Coe ae OS fa oon a ee oh Pee matic rachis with two spikelets rachis is continuous (not. disartic- SHESSILE SPIKELETS IN TWO-SIDED SPIKES 37 is always above the first glume. When no glume is found below the first floret, it is obvious that it is the first glume which is suppressed. In Fig. 28 (Lepturus cylindrn- cus) we have a greatly thickened, strongly nerved rachis with spike- lets placed as in Fig. 27 but reduced to the second glume and a single floret. This little spikelet is sunken in the hollow of the rachis joint, the second glume fitting snugly over the hollow, the whole forming a long, slender, wiry cylinder. At maturity the rachis disarticulates with the spikelets firmly embedded in the joints. (See diagram of rachis, Fig. 28, B, and, above, a joint with spikelet removed, show- ing the hollow, and a second with the spikelet in position.) The plant bearing these spikes grows along _ mud fiats near the sea. The rachis joints are cylindrical and readily roll down the slope to the water. Being corky, they are carried by the lightest ripples and are thus spread over wide areas. The grain Wie. 25 As spartnot spike of JLepturus cylindricus; B, dia- gram of rachis, spikelets removed; above, diagram of | single joint. germinates within its little cell, and the young roots and leaves push aside the water-soaked glume. 38 FIRST BOOK OF GRASSES Returning to Fig. 25 with its one spikelet at each joint, flat against the rachis, compare with it Fig. 29 (Elymus wir- ginicus, or” rye-grass). In this there are two spikelets at, each joint of the rachis, the first glumes back to back, the spikelets somewhat j distorted, each pair reaching around the edges of the rachis. The / figure shows a pair of spikelets and two joints pair of spikelets next above, on the opposite side.of the rachis, lightly sketched in behind; two rachis, with spikelets re- moved, are shown by dotted lines. A _ dia- srammatic sketch of a pair of spikelets, the dis- Fie. 29. A, pair of spikelets of Ely- Ned reduced, is shown mus virginicus; B, diagrammatic above. A comparison of figure of the pair of spikelets. the diagrammatic spike- let with the spikelet in Fig. 25 will show the structural similarity. In their natural position the spikelets, of the rachis, with the more internodes of the ‘ F ———- eS eS ee . = SESSILE SPIKELETS IN TWO-SIDED SPIKES 39 overlapping on the short joints and extending around the edges of the rachis, so that at least one is seen nearly edge-wise, form a spike that may well be con- fusing to the beginner, especially when, as in the species shown in Fig. 29 and several others, the glumes stand out like a 4-rayed involucre below the ap- pressed florets. However, a single joint with its spikelets attached cut out of the spike readily dis- closes the structure. In some species of Elymus there are three spikelets and occasionally four or five at a node, the distortion being correspondingly greater. In several species the glumes are so narrow as to appear like bristles or awns only. In most of the species the rachis is continuous and can not be disjointed. In a closely related genus, Sitanion, the rachis disarticulates at the base of each joint, the slender rigid joint remaining as a tiny sharp-pointed stem below the cluster of long-awned spikelets. The awn-like glumes of Sitanion commonly split between the nerves, sometimes to the very base, appearing like a cluster of awns below the florets. In Elymus and Sitanion the spikelets are all alike (or some occasionally variously aborted) and all sessile (set directly on the rachis). In Fig. 30 (Hor- deum nodosum, one of the wild barleys), a group of three spikelets and a joint of the rachis are shown. As in Sitanion the rachis disarticulates at the base of the internode, the joint remaining attached to the spikelets above it. Note that the central spikelet is sessile and the lateral ones pediceled, that the lower 40 FIRST BOOK OF GRASSES floret of the central spikelet is well developed while those of the lateral florets are rudimentary, and that the back of the floret is turned from the rachis with the glumes (bristle-like in this species) at the sides or back, contrary to the arrangement characteristic of grass spikelets. The problem of the glumes in Hordeum has not been satisfactorily solved. It appears prob- able that the reduced rachilla joint between the second glume and the floret is twisted and bent inward, bring- ing the glumes at the side or back of the floret. In the culti- vated barley the rachis Fia. 30. ie ie: of Hcrdeum does not break up, as- in the wild species, the continuous rachis having been fixed by selection. The florets fall from the spike in thrashing, or in naked or hull-less barley the grains fall from the ~ lemma and palea, as in wheat. In cultivated 2-rowed barley the lateral spikelets are pediceled and sterile, as In the wild species, but in 4-rowed and 6-rowed barley the lateral spikelets are sessile and fertile, characters fixed by selection. The grasses characterized by the spicate in- SESSILE SPIKELETS IN TWO-SIDED SPIKES 41 florescence dealt with in this lesson form the barley tribe, which from the standpoint of man is the most important group of grasses, if not of all plants, in the world, containing wheat, barley, and rye. SUMMARY The specialization in spicate inflorescence is chiefly in the rachis and next in the position of the relatively simple spikelets. When the glumes are distorted, standing side by side, as often found in species of Elymus, or when one of them is suppressed, we can tell which is which from the fact that the first, or lowermost, floret is always above or on the same side of the spikelet as the first glume. REVIEW Collect heads of wheat, rye, barley, quack-grass, species of Elymus, Lolium, or squirrel-tail grass (one or more of these will be found anywhere in the United States). Note whether the rachis readily disjoints. If so, separate out a single joint with the spikelets attached. Note where the rachis breaks, at the summit or base of the joint; note the number of spikelets at a . joint and the number of florets to a spikelet. Distinguish the individual spikelets and their parts. If the rachis does not dis- joint, cut across the middle of the internodes, taking out a single joint with attached spikelets. Note the number of spikelets to a joint; whether there are one or two to several fertile florets to the spikelet and whether the spikelet is placed flatwise or edgewise — to the rachis. Note how spikes bearing spikelets with scabrous awns push themselves forward when handled. LESSON VI PEDICELED SPIKELETS WITH LARGE GLUMES AND OTHER MODIFICATIONS TURNING again to the spikelet of Bromus secalinus (Fig. 11), compare with it Fig. 31 (wild oats, Avena fatua). The olumes are greatly enlarged and the rachilla joints are so short that the florets appear to be almost oppo- site. The awn, instead of extend- ing from the apex of the lemma, pro- trudes from the back and (a6 twisted for about half its length. We noted in Les- son IV that the awn is an exten- sion of the mid- nerve. This fact is well shown in the floret of wild oats (Fig. 31, B, the floret seen from the back), in 42 Fig. 31. A, spikelet of Avena fatua; B, floret. PEDICELED SPIKELETS WITH LARGE GLUMES 43 -. which the midnerve leaves the body of the lemma about the middle of its back and becomes a free awn, while the lemma above the departure of the awn is nerveless. This is invariably the case when Fre. 32. Spikelet of Trisetum spicatum. the awn is dorsal (that is, pro- - truding from the back); the lemma is always nerveless above it. Compare Figs. 31 and 32 (Trisetum spicatum). It will be seen that they are the same type of spikelet. In Trisetum the awn is loosely twisted Fia. 33. Spikelet of Danthonia and 1s borne etsy the ap si spicata; floret above. of the lemma, which is tipped | with two slender teeth. | In Danthonia spicata (Fig. 33) the fiorets are more numerous and are smaller in proportion to the glumes. The broad strongly twisted awn arises from a4 FIRST BOOK OF GRASSES between the teeth or lobes of a bidentate (2-toothed) apex (see floret above, seen from the back). In these three spikelets, as in all but a few of the erasses of the oat tribe, the florets fall from the glumes which remain on the pedicel. In velvet grass, Notholcus lanatus (Fig. 34), the spikelet falls entire. The articulation of the spikelet, taken throughout the grass family, is so nearly uniform for related genera that it is relied on to differentiate large series. (See Lesson IT, on inflorescence). J There are exceptions to the ia. 34. A, spikelet of aode of articulation character- Notholeus lanatus; B, istic of the group as a whole pair of florets. : : in the. case of a few genera in three of our tribes. Such exceptions are puzzling to the beginner, leading him astray in using keys. We must learn to observe all the characters of the inflorescence and base our judgment on the sum total of the characters, remembering that ‘‘Nature does as she pleases”’ and rejoicing that in grasses she at least pleases to keep invariably to the 2-ranked arrangement of the spikelets. (See the summary of Lesson II). In Lesson IV, Figs. 18 and 19, we observed spikelets in which the florets were of two kinds. In Notholcus lanatus the lower floret is per- fect and awnless and the upper is staminate and bears a hook-like awn from the back (Fig. 34, B, ly, py ZG; PEDICELED SPIKELETS WITH LARGE GLUMES 45 florets removed from the glumes. Note the curved and exceptionally long lowermost rachilla joint.) In Sphenopholis, closely related to Trisetum _ (Fig. 32), the spikelets fall entire, as in velvet-grass. In tall oat-grass (Arrhenatherum elatius) the spikelets bear one perfect awnless floret and one staminate awned floret, as in velvet-grass, but their position is reversed, the staminate being below and the perfect above. SUMMARY In the oat and its relatives the large glumes and the awn of the lemmas are the most prominent characters, although in species of some genera the awn is wanting. Pubescence is commonly con- spicuous. ‘The inflorescence is an open or contracted panicle. REVIEW Collect panicles of wild oats or awned specimens of cultivated. oats (cultivated oats growing wild commonly bear awns), of Danthonia, one or more species of which are to be found through- out most of the United States, and any of the related grasses available, and examine the spikelets. Place a floret with a - twisted awn in a drop of water and observe the result. In awn- less florets of cultivated oats note that the midnerve of the lemma, if it is not at all produced into an awn, stops abruptly at the point where the awn would arise normally and that the lemma is nerveless above this point, just as if it were awned. LESSON VII PEDICELED ONE-FLOWERED SPIKELETS Turn to the spikelet of wild oats (Fig. 31) and in imagination eliminate all but the lowest floret and the glumes. Better still, with a spikelet of oats in hand break off all above the lowest floret. Now we have a large model or pattern of the reduced spikelet of a very large number of grasses, red-top, timothy, and their kind. Examine Calamagrostis canadensis (Fig. 35, the floret raised from its glumes) and note how it corre- sponds to the pattern obtained by reducing the spikelet of oats to a single floret. The only / vestige remaining of the other joint back of the palea (shown, exaggerated somewhat, in Fig. 30). In all but a few genera the Fic. 35. Spikelet of Cala- . . . magrostis canadensis, Yachilla is entirely suppre ce Compare Fig. 35 with Fig. 32 and note that Trisetum reduced to a single floret would closely resemble Calamagrostis. In Agrostis (Fig. 36) the rachilla is normally suppressed. In two species in the far West it is present as a minute rudiment. In most of the species 46 florets is the minute rachilla ee Ae ee a ee PEDICELED ONE-FLOWERED SPIKELETS 47 the palea also is suppressed or represented by a rudiment only (Fig. 36, Agrostis hiemalis, the floret with palea wanting, raised from the glumes). Here we have specialization through elimination, the spikelet reduced almost to its lowest terms, one floret with no palea, no awn, no callus hairs. In this particular species the very open panicles break off and roll before the wind as tumbleweeds, scattering the we. 36. spike- seed. Several species of Agrostis have [< SZ ie our native grasses, form- S Bes Up eS ing the genus Amphicar- EIA NN pon, related to Panicum, Fic. 72. Base of plant of Amphi- : carpon Purshit. are remarkable in that they produce large cleistogamous spikelets under- ground from subterranean branches (Fig. 72). The plants also bear terminal panicles of ordinary and much smaller spikelets, but these seldom perfect seed. SUMMARY In Panicee, the millet tribe, the spikelets fall entire. They bear one perfect floret with a sterile floret below it. The lemma and palea of the perfect floret are indurate. The sterile lemma resembles the second glume, the two simulating a pair of glumes, while the first glume is small and looks like an addi- 78 . FIRST BOOK OF GRASSES tional one (in some older works it is called the acces- sory valve or glume) or is entirely suppressed. The genera differ chiefly in the arrangement of the spike- lets in the inflorescence. In afew genera some of the panicle branches are without spikelets and are transformed into bristles or burs. REVIEW Collect the inflorescence of broom-corn millet, old witch-grass, or of as many species of Panicum as are available, and dissect the spikelets. Collect heads of barnyard-grass and compare the spikelets with those of Panicum. Compare the spine-like hairs with those of Nazia, Fig. 54. - | Collect the inflorescence of crab-grass and of any species of Paspalum available; note the arrangement of spikelets and com- pare the form and texture of the fruit (fertile floret) with that of Panicum. Collect heads of common millet or of yellow or green foxtail. Remove enough branches from the axis to show clearly the form and arrangement of the few remaining. If available, examine a sand-bur, splitting the bur with a sharp knife. | | LESSON XI PAIRED SPIKELETS WITH HARDENED GLUMES AND THIN LEMMAS In the sorghum tribe, which we are about to study, the spikelet, as in the millet tribe, falls entire and is dorsally compressed, but the glumes are hardened and the lemmas thin, while in the millet tribe the glumes are thin and the fertile lemma and palea are hardened. The glumes entirely inclose the two florets. The midnerve of the first glume is com- monly suppressed, while a pair of nerves near the margin is often prominent and sometimes keeled, or — even winged. ‘he second glume may be like the first or the midnerve may be slightly keeled. The lower floret consists of an empty lemma only, the upper of a perfect flower with a small thin often awned lemma (sometimes so small as to appear like a bit of membrane at the base of the awn) and a minute palea (sometimes suppressed). Examine Fig. 73, A, and compare it with Figs. 21 (p. 30), 22 (p. 31), 30 (p. 40), 40 (p. 49), 52 (p. 61), and 53 (p. 62). In all the figures referred to, fertile spikelets are associated with sterile ones. These are grouped in various ways. In the sorghum tribe the typical arrangement is a jointed raceme with a sessile perfect spikelet and a pediceled sterile spikelet , 79 80 FIRST BOOK OF GRASSES (staminate or neuter) at each joint, the rachis dis- articulating at the summit of each joint, this and the pedicel of the sterile spikelet remaining attached at | their base to the per- ) fect spikelet as a pair of little stalks. In |/ this group of grasses - specialization consists chiefly in modifications of the axes of inflores- cence and secondarily in the modification of the spikelets. In Fig. 73, A (Johnson-grass, Holcus halepensis), are two views of a single joint, consisting of the sessile perfect spikelet ‘( with the attached ra- i chis joint and the ped- “4 icel with its staminate iV, spikelet. Fig. 73, B, is ~ a diagram of a raceme Fie. 73, A, two views of single joint of four such joints and of raceme of Holcus halepensis; B, 73, C, a, diagram of the diagram of raceme of four joints; i i C, diagram of rachis and pedicels; D, rachis and pedicels, the ie ee spikelets removed and the points of disarticulation shown by dotted lines. In sorghum, or Holceus, these little racemes are borne on the ultimate branchlets of a panicle (Fig. 73, D). iin SV — . It y Y y < PAIRED SPIKELETS 81 In the closely related Indian-grass, Sorghastrum, the racemes are reduced to one or two joints, and the sterile spikelets are wholly suppressed, the slender hairy pedicel alone being developed. Compare Fig. 74, A, a diagram- matic single joint of Hrianthus sac- charoides, with Fig. 73, A, and Fig. 74, B, three joints of a long raceme, with Fig. 73, B. It will be seen that, while the spikelets are pared, the pedi- _~ celed spikelet is as large as the sessile one and, like it, is awned. In this genus the pediceled spikelet is usually perfect. The ra- -eemes are long and slender and _ co- piously hairy, and are crowded on a Fig. 74, A, diagram of single joint of raceme of Erianthus saccharoides; B, three joints of raceme. stout main axis forming large, dense, woolly panicles. In sugar-cane the inflores- cence is like that of Erianthus, but the spikelets are awnless. 82 FIRST BOOK OF GRASSES Examine Fig. 75, A, a joint of a raceme of one of the broom sedges (Andropogon scoparius). It will be seen to have the same general plan as a joint of sorghum, and the racemes, shown in Fig. 75, B, im though slender and flex- uous, are in structure similar to the racemes of sorghum. The entire in- florescence, however, is very different. In sorg- hum and Erianthus the j; inflorescence is a leafless , terminal panicle, such as is common in grasses. The diagrammatic inflores- cence (Fig. 75, B) shows Mi that the racemes of the | } broom-sedge are borne on Hie 75. A, single joint of raceme a aeatcrcaas slender lealy of Andropogon scoparius; B, branches arising in the SE fempound into axils of | leaves) amen main culm or branches, the whole forming a compound inflorescence. The leaves, especially the ultimate ones immediately below the racemes, are mostly reduced to blade- less sheaths and are sometimes bright colored. Such transformed leaves subtending or surround- ing single inflorescences are commonly termed spathes. In some species the racemes are partly inclosed