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multicellular glandular hairs (Fig. 39, 5) (cf. Woopnear) 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 # 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 Secersrenr 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. 
I have not examined the roots. 
Summary of the Zricacew. 
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-tissue; 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 
