CREPIS

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Crepis is generally recognized by the rosettes of coarse, often pinnately lobed leaves, erect heads, epaleate receptacles, calyculate involucres, yellow corollas, subcylindric or fusiform, ribbed cypselae, and pappi of barbellulate bristles. The taxonomy and evolutionary relationships of Crepis were studied by E. B. Babcock (1947) and his associates. Their work was thorough and important because of the effort to incorporate cytogenetic information in the evolutionary analysis. Extensive survey of chromosome number and karyotype indicated two major ploidy groups in Crepis, corresponding to New World and Old World species complexes. Of the 12 species of Crepis native to North America, 10 are polyploids with x = 11. The core diploid populations commonly occupy discrete ecologic zones and are thought to be entirely distinct from one another, yet they are interconnected by a continuous complex series of intergrading polyploid forms that are partly or completely apomictic (Babcock). The polyploids are of two forms, autopolyploids that are similar to the diploids, and allopolyploids that combine the characteristics of two or more diploid species. The allopolyploid forms of hybrid origin may exhibit the characteristics of multiple parental species and therefore are difficult to classify. Some of the heterogeneous apomictic populations, or groups of populations, have been grouped together and recognized as subspecies; those taxa are often difficult to identify and further study is clearly needed. Despite these difficulties, the subspecific taxa of Babcock were tentatively included in the present study. The Old World species are mostly diploid (n = 3, 4, 5, or 6). Babcock concluded that there was a progressive decrease in the chromosome numbers, from n = 6 to n = 3. Along with the decrease is a corresponding increase in chromosome asymmetry and reduction in chromosome length.

Facts about "CREPIS"
apex shapeacute +, acuminate +, tapered + and beaked +
array architecturecymiform +, corymbiform + and paniculiform +
base shapekeeled +
base widththickened +
blade shapeelliptic +, ovate +, lanceolate +, linear +, spatulate +, oblanceolate +, lyrate + and runcinate +
bractlet shapesubulate +, lanceolate + and deltate +
bractlet sizereduced +
bristle architecturebarbellulate +
bristle colorationwhite + and tawny +
bristle external texturecoarse +
bristle fusiondistinct + and connate +
bristle height or lengthshorter +
bristle positionouter +
bristle variabilityequal +
bristle widthfine +
calyculus external textureglabrous +, tomentulose + and setose +
calyculus sizeunequal +
caudex internal texturewoody +
chromosome count3 +, 4 +, 5 +, 6 + and 11 +
corolla colorationyellow +, orange +, white +, pink + and reddish +
cypsela architecturemonomorphic +
cypsela colorationyellow +, brown +, green +, red + and black +
cypsela course or orientationcurved +
cypsela habitdimorphic +
cypsela shapesubcylindric +, fusiform +, terete + and subterete +
distally shapelobing +
face architecture or exudationstipitate-glandular +
face external textureglabrous +, tomentose +, setose +, with appressed hairs + and hispidulous +
face positionadaxial +
hair architecture or exudationstipitate-glandular +
hair orientationappressed +
head arrangementsingly +
head orientationerect +
involucre shapecylindric +, campanulate + and turbinate +
keel prominencepronounced +
leaf architecturepetiolate +
leaf positionbasal + and cauline +
lobe countpresent +
lobe positioncauline +
lobe shapetoothed +, lobed + and entire +
lobe sizereduced +
margin shapeentire +, dentate +, serrate +, toothed + and lobed +
palea widthnarrow + and thin +
pappus behaviourfalling +
pappus durationpersistent +
peduncle architecturebracteate +
peduncle shapeinflated +
petiole architecturewinged +
phyllary colorationgreen + and yellowish +
phyllary external texturescarious +
phyllary shapelanceolate +
phyllary sizesubequal +
phyllary variabilityequal +
receptacle architectureepaleate + and paleate +
receptacle external textureglabrous + and hairy +
receptacle reliefpitted +
receptacle shapeflat + and convex +
rib external texture or internal texturespiculate-roughened +
root depthdeep + and shallow +
root internal texturewoody + and fibrous +
series count1 +
stem architecturesimple + and branched +
stem coloration or external texture or reliefstriate +
stem external textureglabrous +, hairy +, hispid + and setose +
stem habitdecumbent +
stem orientationerect +
whole organism architecturetaprooted + and rhizomatous +
whole organism life styleannual +, biennial + and perennial +