70 Transactions. 



exceptions in the eases of miro,f niatai, and Dacrydiuni Kirhii. 

 It might be noted here again the frequent occurrence in the 

 Podocarpece of tannin-sacs in the layer next to the epidermis. 

 Daguillon does not mention anything of the kind as occurring 

 in the Abietinece. 



6. It is interesting to note the almost complete absence of 

 " pericyclic sclerenchyma " in the Podocarpece ; one or two 

 isolated fibres alone occur. The only strengthening development 

 here is the row of sclerenchyma cells round the resin-canal. 

 This must, however, form a very strong support for the leaf, 

 owing to the arrangement of these cells in a circle. Daguillon 

 also notes the presence of transfusion tissue in the pericycle, 

 but its distribution is very different in the two groups. In the 

 Abietinece it generally extends right around the bundle, often 

 appearing to be connected with the phloem ; in the Podocarpece 

 this tissue generally occurs in groups at the sides of the bundle. 

 From the position of the transfusion tracheids, as shown in 

 Daguillon's figures, it seems more likely that they originated 

 from the centrifugal than from the centripetal xylem. Daguillon 

 himself says nothing about their origin, evidently regarding 

 them as modified pericyclic cells. Tannin-sacs occur in the 

 pericycle of many Podocarpece. 



7. A bifurcation of the bundle like that occurring in the 

 later stages of the Abietinece does not occur in the Podo- 

 carpece. The bundles of the mature leaves are, however, 

 broken up by medullary rays. It is in the case of a co- 

 tyledon — i.e., that of totara — that we find the most parallel 

 development. 



8. In both groups the " number of conducting elements of 

 the xylem and of the phloem augments when the primordial 

 passes into the mature leaf." 



9. In both groups also " when the parenchyma is hetero- 

 geneous and bifacial the differentiation of the palisade paren- 

 I'livma is generally accentuated in the adult leaves." 



We see from this summary and comparison that in the 

 Abietinece there are many anatomical developments similar to 

 those we have noted in some of the Podocarpeo?. This similarity 

 in development must not be confounded with the entirely different 

 matter — similarity of structure. The leaves of the two groups 

 are generally very different both in external form and in the 

 arrangement of their component anatomical elements. But in 

 both groups, to put the mutter generally, disregarding all specific 

 differences, the development tends to the differentiation of 

 tissues for protection and strength, and also, both in the bundle 

 and in the parenchyma, to modifications for increasing the 

 power of conduction. 



