226 



are spread out or re flexed. In spring and early summer the 

 plant developes leaves (see fig. 52) which are linear-lanceolate, 

 2 3 centimetres long, and white-haired, but the leaves fall 

 off later in the summer so that the branches become the 

 only assimilating organs. In late summer the larger plants 

 are leafless, globular and spiny shrubs. The spines are 

 formed by the year-shoot branches of secondary and tertian 7 



Fig. 53. Convolvulus erinaceus. A, Transverse section of the green cortex 



and part of the wood; two vessels are represented; c, Cambium; I, Secreting 



cell. B, Stoma. C, Epidermis with hairs, seen from above. D, A similar 



view of Convolvulus fruticosus. (X 203). 



order, and also by the uppermost ones of primary order 

 which as a rule have formed only one internode and the 

 beginning of a second one when growth ceases, hence the 

 branch remains as a spine, terminated by a dead, withered 

 point. 



The white flowers occur singly on these small branches, 

 and open in June and July. AITCHISON says that they open 

 at sunrise, but I have found them open in the middle of the 

 day in a broiling sun. 



