668 ULMUS 



U. montana With, (vvych elm) and U. campestris L. (elm) in Brit. 

 Growth sympodial, the term, bud being suppressed. L asymmetri- 

 cal, one side larger than the other (cf. Begonia). The fls. are 

 and come out before the 1. as little reddish tufts, each a short axis 

 with a number of 1., beginning 2-ranked at the base and going over 

 to 5-ranked above. There are no fls. in the axils of the lowest to or 

 12 ; in the axils of the upper 1. are fls. arranged in small dich. cymes 

 (cf. Betulaceae), which are reduced, in U. campestris and others, to 

 the one central fl. Each fl. has ?4 8 and as many sta. with i-loc. 

 ovary. [See Chalazogamae.] Fr. a samara. The elm supplies a 

 valuable timber. 



Umbel, an infl. in which the stalks of the fls. all spring from the top of 

 the main stalk. 



Umbellales (BH.}. The i5th order of Polypetalae. 



Umbelliferae (EP., BH.}. Dicots. (Archichl. Umbelliflorae). 200 gen., 

 2700 sp., cosmop., chiefly N. temp. Many in Brit. Most can be 

 recognized by habit ; herbs with stout stems, hollow internodes, and 

 alt. exstip. sheathing 1. with their blades much divided pinnately. A 

 few, e.g. Hydrocotyle and Bupleurum, have entire 1. Infl. usu. a 

 cpd. umbel. At the top of the stalk of each partial umbel, an invol. 

 of bracts is often found (the bracts of the outer fls.), and a similar 

 larger invol. often occurs at the top of the main stalk bearing the cpd. 

 umbel ; the latter is sometimes termed the involucre in contradis- 

 tinction to the involucels of the partial umbels. A term. fl. often 

 occurs, e.g. in Daucus. In a number of genera (e.g. Astrantia, Hydro- 

 cotyle) simple umbels occur, cymose in type (as the non-centripetal 

 order of opening of fls. shows) and often arranged in cymose groupings, 

 e.g. in Sanicula. Eryngium has a cymose head. Some sp. of Xan- 

 thosia and Azorella have such cymose infls. reduced to single fls., and 

 these infls. have commonly invols. of bracts. 



Fl. usu. 5 and reg. (see below), epig. K 5, usu. very small, the 

 odd sepal post. ; 5 (rarely o), usu. white or yellow; A -,, intr. ; 

 G (2), antero-post., 2-loc. ; in each loc. one pend. ovule, anatr., with 

 ventral raphe. On top of the ovary is an epig. disc, prolonged into 

 two short styles. 



The massing of the fls. into dense infls. makes them conspic. 

 (cf. Compositae), and this is aided by the zygomorphism of the C often 

 seen; the outer petals of the outer fls. are drawn 

 out (cf. Cruciferae) so as to form a sort of ray. 

 Honey is secreted by the disc; it is accessible to 

 all insects (fam. in class A). The chief visitors 

 are flies ; fls. very protandrous, the cf stage being 

 most commonly over before the ? begins. 



The ovary ripens into a very char, fruit, a dry 

 schizocarp, which splits down the septum between 

 cpls. into 2 mericarps, each containing one seed. 

 The two are generally held together at first by a 

 thin stalk (carpophore} running up between them. Floral diagram. 

 The structure of the pericarp is of great import- 

 ance in determining the gen. It is nearly always necessary to have 

 ripe fr. in order to identify one of the U. The shape is often im- 



