498 Watson. — Structure and Origin of U to dendroid Scar. 
10. The increase in diameter of lepidodendroid stems, owing to 
secondary growth, is very slight. 
11. The growing points of Lcpidodendron must have been of very 
great size. 
I wish to express my thanks to Professor Sir T. H. Holland, in whose 
department in Manchester this paper was written some time ago, and to 
Professor F. E. Weiss and Dr. D. PI. Scott, for advice and criticism in 
relation to it. 
EXPLANATION OF PLATE XXXVIII. 
Illustrating Mr. Watson’s paper on the Structure and Origin of the Ulodendroid Scar. 
Fig. 1. ‘ Wild’s UlodendronC Transverse section of a large stem giving off a lateral branch, 
the stele of which is just cut tangentially at the extreme top of the photograph. The lighter 
coloured tissue surrounding this stele and the corresponding light area in the main stem are the 
middle cortex. The separative tissue is clearly seen cutting across this, and at the extreme right it 
comes in contact with the periderm of the main stem. Specimen in the Manchester Museum. 
Fig. 2. Transverse section of a stem of Lepidophloios Harcourtii , showing a lateral branch in 
median longitudinal section. This is fully described in the text, p. 491. A 20, D. M. S. Watson 
Collection. 
Fig. 3. Ulodendron viajus. Photograph ot an exceptionally well-preserved scar ; everything 
visible is on a coal film and hence represents the real exterior surface. Further described at p. 489. 
X. I., Manchester Museum. 
Fig. 4. Ulodendron. Photograph of a scar still retaining some of its coal film. Further 
described at p. 490. X. I., Manchester Museum. 
