Pinus is a genus of coniferous trees that are xeromorphic with tracheids instead of vessels in the xylem and albuminous cells instead of companion cells in the phloem. They are seed-bearing plants that produce two types of spores, megaspores and microspores, in separate heterosporous cones on the same monoecious tree, with megaspores in megasporangia on female cone scales and microspores in microsporangia on male cone scales, and wind pollination leads to fertilization through pollen tube development.

1. PHYLUM
CONIFEROPHYTA
Pinus

2. Characteristics
• Big trees with xeromorphic features
• Vascular
o Xylem has no vessels, only tracheid present
o Phloem has no companion cells, but has albuminous cells
• Seed-bearing plants, no fruits
o Naked seeds (no ovary to protect ovule)
• Dominant sporophyte generation (2n)

3. Reproductive Structure: CONES
• Monoecious
o Having both M & F reproductive organs
in the same plant
• Heterosporous
o Producing 2 types of spores
• Megaspore found in megasporangia.
Each scale in cone has 2 megasporangia at
upper surface of the scale in F cone.
• Microspore (pollen grain) produced by
microsporangia. Each scale has 2
microsporangia at the lower surface of
the scale in M cone.
• Pollination by wind
• Fertilization is siphonogamous
o Pollen tubes are developed to fertilize the
F gametes