ARID PORTIONS OF SOUTH AUSTRALIA. 129 



are on both sides of the leaves, or there is but little difference between 

 the dorsal and the ventral sides in this regard. The leaf-structure 

 of E. rotundifolia is also dorsiventral. In this species there is no well- 

 marked palisade, but fairly small cells, somewhat elongated in a di- 

 rection at right angles to the leaf-surface, constitute a distinct stratum 

 on both sides of the leaf. The cells of these strata have the appearance 

 of paUsade cells which have undergone division by cross-walls sub- 

 sequent to the formation as such, but this procedure probably did 

 not take place. A somewhat similar condition, but not so noticeable, 

 is to be seen in E. neglecta. As will appear presently, only in Pholidia 

 scoparia and in Eremophila longifolia, of the species having well- 

 defined palisade tissue, is there a covering of hairs. In the latter 

 species the covering is sparse and in the former it is of a peculiar type 

 and not heavy. The correlation between leaf-cover and the presence 

 of palisade tissue and the dorsiventral condition of the leaf apparently 

 breaks down in E. oppositifolia, which has both of these features, the 

 cover hairs being present in abundance. It was noted, also, that the 

 walls of the epidermis of the species were heavy. All of these features 

 might point to the need of relatively good water-relations of the species, 

 but this remark needs further observation to substantiate it. 



The cover-hairs are various. In E. freelingii they consist of a single 

 row of cells with fairly heavy walls. The cover-hairs of E. brownii 

 appear to be only of this kind, although Solereder states that branched 

 trichomes occur in the species. Both the simple and the branched 

 types of cover-hairs weie found in E. neglecta stems, although only 

 the former, and that sparingly, occur on the leaves of the species. 

 In E. alternifolia (fig. 18) and rotundifolia theie were no proper tri- 

 chomes of either kind above described, but the epidermal cells of the 

 young stems, and not of the leaves, project as short papillae. In E. 

 neglecta there appear to be such papillate cells also, but not to the 

 exclusion of cover-hairs and not in abundance. In the two species 

 mentioned such epidermal cells are wanting in the leaves, nor are cover- 

 hairs present. It is possible, therefore, that the papillate cells may be 

 considered as simple cover-hairs. The leaves and stem of Pholidia 

 scoparia bear shield-shaped trichomes which generally have a short 

 stalk and are closely pressed to the leaf-surface. In young leaves and 

 stems, at least, they overlap and form a very perfect cover. 



Ftjsanus acuminatus. 



The leaves of Fusanus acuminatus are fairly large, narrow-lance- 

 olate, and rather thick. There appears to be no structural difference 

 between the dorsal and the ventral sides. The following may be said 

 to be the most striking structural features of the leaves: The chlor- 

 enchyma consists of relatively short palisade cells which maintain this 

 character throughout. Crystals are to be found scattered through the 



