THE LOWER DICOTYLEDONS. 333 



keeps out short-tongued insects ; this is especially marked in 

 flowers like those of Quince, which are largely visited by bees 

 (the shorter- ton gued ones only getting pollen) and whose 

 receptacle is often bored by the bees. The flowers are often 

 more or less protogynous (Hawthorn, Sloe, Avens, Bird 

 Cherry, Japanese Quince, etc.), though (often in allied forms) 

 sometimes homogamous (Common Cherry, dean, Dropwort, 

 etc.) or protandrous (Roses, Potentillas, Meadowsweet, etc.). 

 Self-pollination is apparently possible in all cases. 



343. The Cow Parsnip or Hogweed (Heracleum sphon- 

 dylium) is one of the commonest, largest, and most easily 

 recognised of British Umbellifers. It grows in moist fields 

 and hedgerows, often beside streams, and in favourable places 

 reaches a height of 5 or even 6 feet. 



The erect annual shoots arise from a short thick rhizome 

 which is perennial, though lasting only a few years. The 

 stem, is hollow, furrowed, and branched a few times in the 

 upper part. The whole plant is more or less rough with 

 short stiff hairs. The leaves are large (often a foot long) 

 and pinnate, with 3, 5, or 7 largo broad leaflets which are 

 toothed and lobed ; there is a good deal of variation in the 

 number, size, and lobing of the leaflets. The base of the 

 leaf -stalk is broad and forms a concave sheath. 



The umbels are compound (Fig. 80), as in most Umbelli- 

 fers, and often measure 4 or 5 inches across. Each has 

 about 20 rays (branches), each ending in an umbel. In 

 many Umbellifers there are bracts below the whole compound 

 umbel, forming the involucre, and bracts below each of the 

 small umbels, forming the involucel, but the Cow Parsnip 

 either has none in either place or else small ones which soon 

 fall off. The whole inflorescence is flat-topped ; when young, 

 it is protected by the sheathing base of the leaf -stalk. 



The flowers (June to September) have an inferior ovary, 

 crowned by a very narrow rim (calyx) with 5 small lobes ; 5 

 white, cream, or pinkish petals, each notched on the outer 

 margin, with a small process arising from the notch and 

 curving inwards ; 5 stamens, alternating with the petals ; and 

 2 short stigmas, surrounded by a honey-disc on the roof of 

 the ovary (Fig. 135 ). The ovary is 2-chambered, with a single 

 ovule hanging from the top of each chamber. The young 



