ANATOMY OF WtddriugtoJiia axd Callitris. 



283 



A part of this section is shown in more detail in Figure 2, 

 where the following points may be noted : (c) the very thick, 

 occasionally ridged, cuticle; (b) the position of the .stomata; 

 (c) the thick-walled hypoderm; (d) the single layer of rather 

 narrow palisade cells; (e) the Tannin-sacs. The position of 

 transfusion cells, conjunctive parenchyma and mesophyll is also 

 indicated. 



A few of the transfusion cells from another section are shown 

 in detail in tigure 3. Bordered pits are present, at least in 

 some cases, but their structure is usually entirely obscured by 

 irregular thickenings of the cell wall protruding into the cavity. 



Fig. 3. 



Fig. 4. 



Fig. 3. Transfusion tracheids, Callitris verrucosa. F = Fibres. (X415.) 

 ,, 4. Stoma of Callitris robusta. G = Guard-cells. (X415.) 



Callitris robusta shows an essentially similar structure, ex- 

 cept that the stomata are to be found on the outer, exposed, 

 surface of the leaf as well as in the angle between two leaves. 

 In the immediate neighbourhood of the stomata the hypoderm 

 is interrupted. A stoma is shown in F"igure 4. Except for 

 differences in thickness of the cuticle the stomata are exactly 

 alike in all three species examined, but of the type normally 

 met with in other Coniferae. The cuticle is by no means so 

 thick in Callitris robusta as it is in C. verrucosa, and, taken as 

 a whole, the xerophytic character of the leaf is clearly much 

 less pronounced in the former species. 



Fig. 5. 



Fig. 6. 



FiE 



Transfusion tracheids, Callitris robusta. (X415.) 

 Part of a transverse section of a leaf base of Widdringtonia cupres- 

 soides. Lettering as before. ( X 145.) 



