ERICOID LEAVES. 



By D. Thoday, M.A. (Cantab.), 

 Professor of Botany, Uni rcrsifj/ of Capefoini. 



[Abstract.) 



Read July 15, 1920. 



A striking- feature of the Maquis of the south-west region 

 of Cape Colony is the hirge number of species with ericoid 

 leaves. These are characterised by a groove, either on the 

 upper or lower side, the stomata being- confined to the epidermis 

 lining the groove, which usually bears numerous hairs. In 

 contrast with tiie Maquis, the flora of the Karroo, if one may 

 judge from observations at Matjesfontein and Prince Albert 

 Eoad, lacks such plants almost entirely. 



A feature of these plants which apparently has not hitherto 

 been noticed is that the grooves vary in the width of their 

 opening with changes in the conditions. If leaves are allowed 

 to dry up, they close their grooves, in many cases completely. 

 Even under natural conditions, during drought the leaves of 

 various species of Erica, of Passerina filifoTmis, of Stilbesp., 

 have been found quite or nearly closed on plants in specially 

 dry situations. Under experimental conditions these species 

 close their grooves when left to transpire without water, and 

 open them again when supplied with water in a moist 

 atmosphere. Some species of Erica, especially E. Phihenetn, 

 also raise and approximate their leaves as they lose water, and 

 spread them again as their water content increases. 



