129 



multicellular glandular hairs (Fig. 39, 5) (cf. Woodhead) which 

 are probably of importance as protective devices in the bud- 

 condition only, if indeed they have any importance in the above 

 connection. Besides these, ordinary unicellular hairs occur in 

 the same situation. The palisade-cells are of one layer only, 

 about 35 p. in height, and loosely connected. The spongy 

 parenchyma is few-layered and has large intercellular spaces. 

 Aqueous tissue and stereom are absent. The whole of the 

 leaf is loosely built. 



The stem. I shall not enter more fully into the structure 

 of the stem, but shall only refer the reader to Segerstedt and 

 Simon. There is no great difference between the spring and 

 summer (or autumn) wood, and the limits between the different 

 annual rings are not very distinct. 



1 have not examined the roots. 



Summary of the Ericaceœ. 



In the present summary I shall briefly compare the chief 

 results arrived at from the special consideration of the biological 

 anatomy of the individual species. I shall begin by comparing 

 the species with each other in regard to protection against the 

 danger of excessive transpiration as indicated by the structure 

 of the leaf; and in regard to the adaptation to light as expressed 

 in the structure of the palisade-tissne; comparing in fact, the 

 separate types of leaf-structure in their relation to external 

 factors. The results thereby arrived at will be viewed in the light 

 of the geographical distribution of each species. In the com- 

 parison of species according to the developmental stage 

 reached by their leaf-structure in relation to the climate, 

 they should, of course, occur in the same habitats or at least 



XXXVI. 9 



