The degree of pubescence on the surface of the twigs varied considerably and was found to frequently follow group location patterns. Thus nearly all of the individuals growing in one field might be found with dense pubescence on the twigs while a similar group several miles away might have, for all practical purposes, no pubescence on the twigs. In general, the most rapidly growing trees (or twigs) had the least amount of pubescence on the twigs.
LEAVES—There was extreme variability found with the leaves of the 158 individual trees observed. All trees were found to have compound leaves, but the leaflet numbers varied greatly. The typical number for shagbark is 5, but 3 to 7 were found; three leaflets were common, 5 were abundant and 7 leaflets were rare. Six cases of leaves with 7 leaflets were obtained from the vast number of leaves checked on the 158 trees; thus the frequency of occurrence is quite low for the group as a whole. Where 7 leaflets were observed, 5 of the leaves were normal pinnately compound leaves (Fig. 4a), while one leaf consisted of five palmately arranged leaflets plus two normal pinnately compound leaflets (Fig. 4b). The leaflets on each tree were fairly uniform in shape but the shape of leaflets between trees varied considerably. Thus one tree might have 5 leaflets quite broadly ovate to obovate in shape while another equally valid shagbark would be found with narrowly elliptical to lanceolate leaflets similar to those of red hickory (oval pignut hickory), Carya ovalis (Wangenh.) Sarg.
[Illustration: Fig. 5a Fig. 5b Fig. 5c
Shagbark Hickory Fruits (1/2X)]
The margins of the leaflets were generally finely serrate and disposed to be ciliate—i.e. with a fringe of hairs along the serrate margins. The presence of cilia tend to differentiate shagbark hickory from red hickory in the field. This feature is a consistently good one if a hand lens is available but the degree of ciliation varies considerably from tree to tree and during different parts of the growing season. The presence of cilia on the margin of the leaflets should not be used as a means of differentiating shagbark from shellbark hickory, Carya lacinoisa (Michx. f.) Loud., since shellbark also has a ciliate margin on the leaflets.
FLOWERS—The female flowers of shagbark are found on short 1 to 5 flowered spikes produced on the current season's growth. Most of the flowers are around 1/3" long, sessile and covered with a tawny tomentum. Each flower tends to have two yellowish green stigmatic lobes but three-lobed stigmas may be found and one case of a 4-lobed stigma was observed. Various amounts of an amber, or yellow scurfy, substance was also observed on the new flowers. The male flowers occur on 3 parted, slender, glandular-hairy aments from the basal portion of the current season's growth. The aments are usually 3-4 inches long with individual flowers consisting of 4 stamens with their surrounding bract and calyx lobes. The anthers are yellowish or greenish yellow. Occasionally a two branched ament may be found but this seems to occur when one branch of the ament has failed to develop due to an injury of some sort. One case of an unbranched ament was observed.
Both female and male flowers are found to be mature after the leaves have grown to nearly their fully expanded mature size. There are more male aments to be found on the lower branches than female spikes of flowers, which would tend to aid in cross pollination of the flowers by wind action. In general the stigmatic lobes are not quite mature at the time that the bulk of the pollen is being shed, yet individual trees, at a considerable distance from another pollen bearing shagbark tree, will bear considerable quantities of nuts indicating self fertility.
FRUIT—The husk of the shagbark is extremely variable in size, shape, thickness and opening habits. In general the husk consists of 4 segments which split along 4 sutures and fall apart at maturity dropping the nut to the ground. In many cases the husk falls to the ground with the nut and does not break apart until it reaches the ground. A few of the trees examined had husks which were not quite deciduous to the base and were retained on the tree until after the nut had been released. One tree among the 158 examined consistently had a 5 parted husk.
The husks varied considerably in thickness, the dried measurements ranging from 1/8 to 1/2 inch with the bulk of the measurements averaging around 1/4" thick. Two trees had husks so thin as to be more typical of red hickory while only 6 trees had husks 1/2 inch thick or more.
The overall shape of the husk around the nut ranged from globose (Fig. 5a) to ovoid (Fig. 5b) to obovate (Fig. 5c).