During seed germination of Justicia procumbens, the formation of lithocysts, trichomes
and diacytic stomata in the epidermis of cotyledons was following a specific distribution pattern.
During the first 1-3 days, many young stomata and trichome initial cells were formed sporadically in
the adaxial and abaxial epidermis, but no lithocyst was found. Three to five days after seed sawing,
two cotyledons were exposed to light and then opened. In the meantime, some lithocysts were
recognized on both adaxial and abaxial epidermises. The lithocysts on the adaxial epidermis occurred
in the radially arranged cells located between the central area and the margin. However on the abaxial
epidermis, they were found only in the marginal cell layer and their axes were along the margin of
cotyledons. The total number of lithocysts in a cotyledon at this stage was 32.2 ± 4.3 and the cystolith
inside the lithocyst was spindle in shape and 48.2 ± 21.1 µm in length. Three weeks after seed sowing,
the cotyledons were mature and the total number of lithocysts in a cotyledon was 112.2 ± 10.1 and
the cystolith in the lithocyst was enlarged to be 119.8 ± 27.8 µm in length. The cystolith was
extracellularly formed in the cell wall of lithocyst. Its surface was with many protuberances and
surrounded by a cystolith sheath connecting to cytoplasmic strands. The core of cystolith was
surrounded by concentrically stratified fibrils and the calcium carbonate was concentrically
accumulated. The waved stratified fibrils were also deposited in the protuberances. The EDX spectra
showed that the main mineral elemental compositions of cystoliths were Ca and P. Ca was deposited
more in the central part of cystolith than in the marginal area.