The northern limit of the distribution of Quercus imbricaria Michx. and Quercus palustris Muench, in the valley of the Iowa River is reached near Hills in Johnson County. Here and southward both species occupy the alluvial bottom lands, and before the extensive clearing of the alluvial forests they were freely intermingled. In view of this fact and of the well-known tendency of oaks to hybridize it is not surprising that forms which are evidently hybrids occur

Shimek, B.

English

University of Northern Iowa

Proceedings of the Iowa Academy of Science Volume 15 Annual Issue Article 11 1908 A Hybrid Oak B. Shimek Copyright ©1908 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Shimek, B. (1908) "A Hybrid Oak," Proceedings of the Iowa Academy of Science, 15(1), 77-83. Available at: https://scholarworks.uni.edu/pias/vol15/iss1/11 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu. A HYBRID OAK. BY B.  SHIMEK. The northern limit o f  the distribution of Quercus imbricaria M ichx. and Quercus palustris Muench, in the valley of the Iowa river i s  reached near Hills in Johnson county. Here and southward both species occupy the alluvial bot­tom lands, and before the extensive clearing of the alluvial forests they were freely intermingled. In view of this fact and of the well-known tendency of oaks to hybridize it  is  not surprising that forms which are evidently ·hybrids occur. It  is obviously difficult to determine the fact that hybridization has taken place in plants which require many years. to reach maturity, when they first fully display their hybrid characters, and the only criterion which m ay be em­ployed is the mingling of recognized specific characters. Where species are very closely related this is  manifestly difficult, if  not impossible, but the task is much easier when the species are a·s well marked as the two here noted. Among the two or three probable hybrids which were found in a scattered clump of Q. imbricaria and Q. palustris on the alluvial bottom land south of Old Man's creek, near Hills,  the one here discussed shows this mingling of the characters of the parent llpecies most clearly. A probable hybrid o f  these species has already been reported by Engelmann. Sargent says o f  it : "The leaves were broadly lanceolate, mostly acute at the apex, and entire or usually furnished with coarse triangular-toothed acute bristle­pointed teeth ; they were pubescent at first, especially on the lower surface, but soon became glabrate, and lustrous above, paler below, from four to six inches long and from one to two inches wide. The fruit was mostly sol itary and was borne on a stout peduncle sometimes half an inch in length ; the nut was oblong, full and rounded at the apex, about as broad as it was long, light brown, and inclosed for about one-third o f  its length in the thin cup-shaped o r  turbinate cup covered by ovate scales rounded at the apex and clothed, except on the bright red-brown margins, with hoary pubescence." It  may b e  of  interest to note that our hybrid agrees substantially with this description, but many of the leaves are ·quite deeply lobed, and these in some cases reach a width of more than three and one-half inches. * Trans . St . Louis Academy of  Sci . , vol . III , p. 539 , 1877 .  Also quoted in Sargent ' s  Silva of North America,  vol . VIII , pp . 176-177 , foot-note 9; 1895 . 7 ( 77 ) 1Shimek: A Hybrid OakPublished by UNI ScholarWorks, 190878 I OWA ACADE MY OF SCIENCE The parent oaks in this case are easily distingui'shed by the following char­acters : Q. palustris DuRoi. Young l eaves : Lower surface quite densely pubescent, with more prominent tufts of hairs in the axils of the large veins. Upper surface with few reddish-brown or purplish club-shaped trichomes. Margins red, not thickened, not revolute. Petioles short. MattlrO Iea-ves : Q u ite regularly 5 to 7-lobed, each lobe long bristle-pointed. Rather thin. Veins rather distinct, the m idrib pro­j ecting above both the upper and J (nvcr surfaces. l\fa rgin scarcely revolute, and not thick­ened. Lower surface smooth, except for tufts of  hairs i n  axils of veins. Dlack 4 to 6 % inches long and 4 to 5 % inches ·wide.  Petioles 1 to 2 inches long, smooth. Flo\.Vf'rs : S t i gmas recurved or spreading, terete, rf' d .  Stam inate flowers with calyx of 4 or 5 ,  n1 of'tly unequal, broad, often irregu­larlv sl ightly lobed sepals, with . la­cin iate m argins, and without abruptly tapering apex. Fruits : C u p  YCrj.,. flat belo\V, shallow, covered with closely appressed tomentum within. A corns sub-spherical or even depressed at apex, and often showing slight longitudinal ribs or angles. Q. imbricaria Michx. Young leaves : Lower surface more densely pubescent, without special prominent tufts in the axils of the l arge veins. Upper surface with numerous reddish­brown or purplish club-shaped tri­chomes. Margins green, thickened, distinctly rev­olute. Petioles long, often nearly equal to blade. Mature leaves : Entire, or somewhat 3 - lobed, and some­times i rregularly repand-lobate on young shoots. Moro leathery. Veins n1ore prominent, the midrib in a groove above, at least in its lower half. Margin usually distinctly thickened, an<l somewhat revolute. Lower surface Quite uniformly pubes­cent. Bln d e  � ;1:: to 4 11z inches l o n g ,  and 1 t o  1 : : �  inches \Viele.  Petioles :;,;, to 11{? inch long, pubescent. 11..,lo\\"ers : Stigmas short, yellowish-green. St;irnin ate flowers with calyx of 4, n1 o�tly equal,  l rtnce-ovute, entire sep­als,  with abruptly tapering tips which arc laciniatc-tufted at the apex. Fru its : Cup somewhat obconical or turbinate, somewhat deeper, the scales rather loose, especially toward margin of cup, and its inner surface nearly smooth. Acorns more conical, and terete. ·with special reference to the characters here brought out the hybrid may be described as follows : fn general aspect and habit it resembles both parents, which are very similar in this respect. 1'he young leaves have the lower surface densely tomentose, without promi­nent tufts in the axils of  the large veins, resembling Q. imbricaria. In other respects the young leaves are intermediate, having margins somewhat revolute, slightly thickened, and in part red, especially toward the base, and with medium petioles. In division of blade the young leaves are also intermediate between the parent species. The mature leaves vary from quite entire to deeply lobed, the sinuses ex­tending fully half way to the midrib. The lobes are rounded or acute, more or less spreading or curved outward at apex, and when distinct terminating in a long bristle point, as in Q. palustris. From one to three lobes may appear on each side, and they are usually unequal and irregular. In texture they re­semble Q .  palustris, but the venation is intermediate i n  prominence and the midrib rises to the level o f  the upper surface, or is  sometimes sl ightly depressed in an imperfect groove at the base of the blade. The margin is 'Somewhat thickened and sometimes slightly revolute. The lower surface is  smooth except for tufts of hairs in most of the axils of large veins and occasional patches o f  scant pubescence, especially toward the base o f  the blade. The blades vary in 2Proceedings of the Iowa Academy of Science, Vol. 15 [1908], No. 1, Art. 11https://scholarworks.uni.edu/pias/vol15/iss1/11IOWA ACADE MY OF SCIENCE 79 length from 414 to 6 inches, and in width from 1 % inches in the entire form to 3% inches in the deeply lobed forms. The petioles vary from % to % of an inch in length, and are smooth or irregularly pubescent. The stigmas resemble those of Q. palustris in form and color. The sepals of the staminate flowers are mostly unequal, broad and somewhat lobed, in these charactern resembling Q. palustris, but being narrower, and showing a some­what tapering rather abrupt tip which is somewhat laciniate tufted, in this respect approaching Q .  imbricaria. The cup is interme diate in form and arrangement of scales and is almost smooth within.  The acorn resembl es some of the more spherical forms of Q .  imbricaria a n d  is also intermediate. I t  will b e  noticed that in form, dimensions and division of the blade, margin, venation, and lower surface of the leaf, the surface of the petiole, the form of the sepals, the form, arrangem ent of scales, inner surface and depth o f  the cup,  and in the form of the acorn , the hybrid is intermediate between the parent species, sometimes approach ing one, sometimes the other. The form and color of the stigmas, and the texture of the leaves are more nearly like those o f  Q .  palustris, but the length of t h e  petiole a n d  t h e  lower surface of t h e  young leaf suggest Q. im bricaria. The accompanying plate s I and I I  illustrate both the p arent species and the hybrid . The hybrid here described is a double tree growing at the eastern edge of a mixed oak grove east of the railroad, in the south half of sec. 2 7 ,  T. 78 ,  R. VI ·w. The following oaks were found in this grove : Q. imbricaria, Q . palustris, Q .  velutina, Q .  macrocarpa, a n d  Q .  imbricaria x palustris.  O n e  of the o aks may be a hybrid,  Q. imbricaria x ve l 11 ti11a,  but this was not satisfactorily determined.  3Shimek: A Hybrid OakPublished by UNI ScholarWorks, 190880 IOWA ACADEMY OF SCI;FJNCE Fig. 1 .  Leaves. ( See p .  8 1 . )  Quercus palustris DuRoi. The two lobed leaves. Quercus imbricaria Michx. The three entire leaves. Fig. 2. Leaves. ( See p.  8 1 . )  Quercus imbricaria x palustris. Three leaves showing variation i n  form . _ ... 4Proceedings of the Iowa Academy of Science, Vol. 15 [1908], No. 1, Art. 11https://scholarworks.uni.edu/pias/vol15/iss1/118 I OWA ACADEMY O F  S C I ENCE PLATE I .  FIG. 1. FIG. 2 . 81  5Shimek: A Hybrid OakPublished by UNI ScholarWorks, 190882 I OWA ACADE M Y  OF SCIENCE Fig.  1 .  Acorns.  ( See p .  8 3 . ) Quercus imbricaria Michx. The four left-hand figures in the lower row. Quercus va lustris DuRoi. The four right-hand fi gures in the lower row. Quercus imbricaria x va lustris . . The upper row. Fig. 2 . Leaves. ( See p. 8 3 . ) Querous im bricaria x palustris. Three leaves showing variation in form. 6Proceedings of the Iowa Academy of Science, Vol. 15 [1908], No. 1, Art. 11https://scholarworks.uni.edu/pias/vol15/iss1/11I OWA ACADEMY OF SCIENCE 83 PLATE I I .  FIG.  1 .  FIG. 2 .  7Shimek: A Hybrid OakPublished by UNI ScholarWorks, 1908

A Hybrid Oak

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A Hybrid Oak

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