表皮
wood cross section
annual ring
background
bark
biology
biotechnology
botany
cambium
cell
cellular
cross section
detail
education
genetic
histology
laboratory
light
magnification
micro
microbiology
micrograph
microscope
microscope wood
microscopic
nature
organisms
photomicrograph
photomicroscopy
pine
pine tree
pine wood
pinus
plant
plant stem
research
science
scientific
sclerenchyma
secondary xylem
section
slide
stele
stem
tree
vascular
vascular cambium
wood
wooden
xylem