THE LOWER DICOTYLEDONS. 331 



340. Some of the commoner Wild Roses are easily identified. The 

 Burnet Rose or Scotch Rose (R. spinosissima) is a small erect 

 bushy plant (1 to 3 ft. high), chiefly found on sand or shingle at the 

 coast, with crowded prickles varying in size and shape, but mostly 

 straight, and passing into mere bristles and glandular hairs ; seven to 

 nine small leaflets ; flowers small, solitary ; fruit nearly black ; sepals 

 persistent and erect on top of " hip." The Sweet Briar (R. rubiginosa) 

 is more closely allied to Dog Rose, but its leaves have a pleasant smell 

 when rubbed owing to an aromatic substance produced by numerous 

 small reddish gland hairs on leaf-stalks and lower side of leaflets ; the 

 prickles are hooked but mixed with bristles and hairs ; flowers usually 

 solitary. The Field Rose (R. arvensia) has leaves and prickles as in 

 Dog Rose, but is a more trailing plant ; the flowers are white, scent- 

 less, in clusters (3 or 4) ; "hip" globular ; sepals not fringed ; styles 

 united into a column which projects from mouth of "hip"; this 

 species keeps on flowering later than the Dog Rose. The Downy 

 Rose (R. villosa) is distinguished from the downy varieties of Dog 

 Rose by the globular fruit, which bears small prickles ; the stem- 

 prickles are straight or only slightly curved, the leaflets downy on 

 both sides. 



341. The Rose Family. One of the chief features dis- 

 tinguishing this large family (Bosaceae) from the Buttercup 

 family is the presence of what is often wrongly called a " calyx- 

 tube." If you imagine a Buttercup flower in which the recep- 

 tacle, during the development of the flower-parts, grows up 

 at the sides as a ring which carries on its edge the sepals, 

 petals, and stamens, leaving the carpels on the central knob, 

 you would have a flower like that of a Cinquefoil, Strawberry, 

 or Blackberry. The cup-like outgrowth involves the sepals 

 more than the other parts, which can easily be detached from 

 the cup. This upgrowth of the receptacle not only tends to 

 enclose and protect the carpels, but also makes the flower 

 tubular and conceals the honey to some extent (there is 

 usually a honey-disc within the bases of the stamens). In 

 Apple, Pear, Hawthorn, Quince, Medlar, etc., the receptacle- 

 cup grows up closely around the carpels, and later on becomes 

 joined to them. 



The great variety of fruits (akenes, drupes, drupelets, fol- 

 licles, and pomes) found in this family is due to various 

 causes the degree of perigyny shown by the flower, per- 

 sistence or non-persistence of receptacle (" calyx-tube "), 

 dryness or fleshiness of pericarp or receptacle, number and 

 form of ripe carpels, etc. 



