i\\RT III.] Beeson: Beehole Borer of Teak. 53 
The writer has not been long enough in one spot to estimate the 
time taken for the formation of the large pore-zone but there are 
indications that it is rapid, i.e., 2 or 3 weeks. A number of trees 
examined in various stages of leaf formation appeared to show that 
the formation of pores is coincident with the appearance of the new 
leaves, but isolated vessels may be formed, when the buds are Swelling 
and only a few have opened. 
The large vessels are first formed singly or in lateral groups of 2 and 
3, and when the bark is removed they separate easily from the cambium 
and appear on the tangential surface of the autumn wood as conspicuous 
ridges. Almost complete pore-zones, one vessel thick, occur when the 
leaves are still limp and not fully expanded, and a certain amount of 
intervascular tissue is formed before the flush of leaves is complete. 
The short time occupied in the formation of the pore-ring gives a 
sharply defined period from which we can date the attack of the borer 
larva. From what is known of the life-cycle it is probable that the 
majority of larvae make the initial excavation in the wood at a time 
when the pore-ring is in active process of formation, and the outermost 
zones of sapwood are flooded with sap. There is, nevertheless, a large 
number of larvae, that make their attacks before or after the pore-ring 
is formed. The criteria by which the date of attack may be determined 
are the effect on the pore-ring and the age of the callus. 
The effect of the three kinds of attack on the pore-ring may now be 
considered. 
1. Before Pore-ring Formation. A larva attacking before growth 
is resumed bores a shallow groove in the autumn wood of the previous 
season. When the cambium renews activity the effect of the injury is 
marked for some distance on all sides of the wound. The vessels formed 
in the pore-ring on the surface of the autumn wood decrease in size and 
thin out as the ring approaches the excavation, and in their place dense. 
homogenous tissue is formed, often inseparable from the wood of the 
previous year. As the annual ring continues to grow the larva enlarges 
its excavation and extends the chamber deeper into the sapwood, cutting 
through the pore-rings of previous years. The criteria by which 
this type of attack is dated are a normally formed pore-ring sharply 
excised by the margins of the sapwood chamber or beehole, followed by 
an abnormal or incomplete pore-ring in which the vessels disappear 
in the direction of the wound. 
2. During Pore-ring Formation, An initial attack taking placS 
while pore formation is in process affects the building of tissues near 
the wound in various ways. If the pore-ring is not far advanced its 
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