86 PLANTS AND saline a 
the Otchids belong, sepals ae petals ssuigity combine 
in form and colour to form one corolla-like envelope 
(then called a perianth). In many other plant groups 
—for instance, the Dipsacacee (such as the Scabious), 
Umbellifere, and Composite—conspicuousness is 
obtained by a grouping together of a large number of 
small flowers. In the Cow Parsnep (Heracleum 
Sphondylium) the outer petal of the marginal flowers 
Fic. 15.—UMBEL OF ASTRANTIA CARNIOLICA, SHOWING PETAL- 
LIKE RING OF COLOURED LEAVES (BRACTS). 4, 
of the large umbel is much enlarged, which enhances 
this effect. In Astrantia, an interesting genus of 
Umbellifere, the bracts take on the appearance of a 
ring of large petals, and surround the group of small 
flowers (Fig. 15). The same thing may be noticed 
in the outer blossoms of the close flower-head of the 
Field Scabious (Knautia arvensis). In many Com- 
posite the process is carried still farther; in the Com- 
