Medullary Spots in Wood. 247 



Explanation of Figures 



Fig. I. Lateral and dorsal views of a larva of Opostega nonstrigella 

 Ch., taken from a twig of Ribes vulgare. (After GrossEnbacher). 



Fig. 2. Young scarcely half-grown dipterous (?) larva taken from a 

 shoot of 5"c7/;.tr rubra Huds. (After Kienitz). 



Fig. 3. Much enlarged lateral view of the head of a larva similar to that 

 in Fig. 2. (After KiEnitz). 



Fig. 4. Lower portion of a peeled mountain ash stem (Sorbus aucuparia 

 L.) showing the lower ends and turning points of three tunnels of which 

 one reaches down into a root. On the cross-section a few pith flecks are 

 visible. (After Kienitz). 



Fig. 5. Cross section of a stem of birch (Betula pubcscens Ehrh.) show- 

 ing numerous pith flecks. Natural size. (After Kienitz.) 



Fig. 6. Cross section of a willow shoot (Salix rubra Huds.) showing a 

 portion of a tunnel deserted by the larva for a long time, (a) New 

 cambium which has been formed to replace that destroyed, (b) Cells which 

 originally belonged to the bark but later became wood cells, (c) Margin 

 or border of the wound formed by the walls of the destroyed cells and 

 excrement of the larva. (d)The layer (c) has been broken through in sev- 

 eral places 'by the outgrowth of the bark cells and the division of the 

 bubble-like 'filling cells' (tyloses?) has begun. From the woody portion 

 only one 'fiUing cell' (e) has emerged; it is from a ray. (After Kien- 

 itz.) 



Fig. 7. Cross section of one-half a pith fleck from a stem of Betula 

 papyrifera Marsh, (a), (a'), (a"), rays, (b) Margin or border almost 

 obliterated, (c) The 'filling cells' are thick walled, densely pitted, and 

 filled with starch. (Original.) 



