60 



WOODPECKERS IN RELATION TO TREES. 



To recapitulate, figures 9A to 9D show wounds 1 year old 

 healed in various ways. Least progress is shown in B and C, in both 

 of which the wound has failed to close. A conical projection is 

 formed on the inside of the bark, which makes a deep depression in 

 following wood layers, as is illustrated by figure 10A. Figures A 

 and D show wounds promptly closed by more vigorous growth. 

 In figure A, as the peck extended only to the sapwood, the succeed- 

 ing annual layer is smooth internally and because of small growth 

 only slightly distorted externally under the bark hole. In figure D 

 one ring of sapwood is entirely and another partly pierced. The 

 new growth has been so thrifty that the original peck has been filled 

 and a plug also pushed out into the bark opening. Methods of heal- 

 ing as illustrated by figures 9 A, 9D, and 10B produce a pit on the 



inner side of the bark which 

 causes corresponding eleva- 

 tions in succeeding layers of 

 wood. As a rule, then, if the 

 growth following sapsucker 

 wounds is vigorous, succeed- 

 ing layers of wood will be 

 bent outward over the 

 wound; if weak, the grain 

 will bend inward. In either 

 case radial sections (fig. 10) 

 of the wood reveal the curl 

 in the grain and tangential 

 sections cutting through the 

 curls show a condition re- 

 sembling natural bird's-eye 

 (PI. IX, fig. 6). As it can 

 usually be recognized from the arrangement of the bird's-eyes in 

 rows (see PI. XII) corresponding to the well-known type of sap- 

 sucker work in the hark, it may well receive the name of sapsucker 

 bird's-eye. 



The question now arises, What is the effect of sapsucker work 

 upon the commercial value of hard maple wood? The bird's-eye 

 and curl, and even small stains if hard and sound, may be considered 

 as ornamental and as enhancing the value of the wood. But exten- 

 sive staining, a common accompaniment of sapsucker, work in hard 

 maple, is detrimental. Furthermore, the original pecks, if on the 

 surface, appear as cavities surrounded by bleached and stained wood 

 (PI. IX, fig. 4), which must be planed off before the wood can be 

 put to decorative use. The strength of the wood is not greatly 

 affected except when pecks are numerous in a single annual layer, 

 in which case (his Layer constitutes an easy splitting plane. 



Fig. 10. — Effects of sapsucker work on wood of sugar 

 maple (.leer saccharum). (From Hopkins.) 



