ADVERTISEMENTS:
Learn about the comparison of habit and anatomy of members of Lyginopteridaceae, Medullosaceae and Cycadales (Based on Bierhorst, 1971):
Comparison # Lyginopteridaceae:
1. Lyginopteridaceae are relatively large and fern-like.
2. Lyginopteridaceaes stems are weak, aerial and well- branched.
ADVERTISEMENTS:
3. Leaves of lyginopteridaceae are bi-pinnate or tri-pinnate, large; ultimate leaf units dissected.
4. In Lyginopteridaceae circinate vernation is seen.
5. In Lyginopteridaceae pinnules had free venation.
6. Stem stele of discrete vascular bundles or protostelic.
ADVERTISEMENTS:
7. Xylem of lyginopteridaceae is in stems mesarch.
8. Leaf traces in lyginopteridaceae develop by tangential division of cauline strand.
9. In Lyginopteridaceae leaf traces is first single and then becoming double.
10. Pith is well-developed in it.
11. Mucilage canals are absent in lyginopteridaceae .
12. In lyginopteridaceae secondary xylem is soft- textured and contains a high proportion of ray tissue and long tapering tracheids.
13. Pericycle are present around the entire vascular region in it.
14. In lyginopteridaceae the secondary growth is monoxylic.
15. In lyginopteridaceae secondary xylem is exocentnc in development.
Comparison # Medullosacceae:
ADVERTISEMENTS:
1. In medullosacceae there are large, fern-like, small trees.
2. Stems of medullosacceae are aerial, erect and un-branched.
3. Leaves of medullosacceae are bi-pinnate or tri-pinnate, large.
4. In medullosacceae vernation is not seen.
ADVERTISEMENTS:
5. Venation was free, pinnate, reticulate or even dichotomous in it.
6. In medullosacceae stems polystelic, advanced types contain a complete cylinder with smaller vascular bundles.
7. Xylem in medullosacceae stems are mesarch.
8. Leaf traces in medullosacceae is not clearly comparable.
ADVERTISEMENTS:
9. Leaf traces is multiple In medullosacceae.
10. In medullosacceae steles embedded in well-developed ground tissue.
11. Mucilage canals are present in stems of medullosacceae.
12. In medullosacceae xylem same as in Lyginopteridaceae.
ADVERTISEMENTS:
13. Pericycle surrounds each stele separately in medullosacceae.
14. The secondary growth in medullosacceae monoxylic.
15. Secondary xylem in medullosacceae is endocentric in majority of the genera.
Comparison # Cycadales:
ADVERTISEMENTS:
1. In cycadales there are medium-sized trees.
2. Stems of cycadales are aerial, columnar, erect, slow-growing, only rarely branched.
ADVERTISEMENTS:
3. Leaves of cycadales once pinnate or bi-pinnate.
4. In cycadales there is circinate vernation in some species.
5. In cycadales there are venation pinnate or open dichotomous.
6. Stems in cycadales are essentially a complete ring.
7. Xylem in cycadales stems are endarch.
8. In cycadales leaf traces develop generally by tangential divisions.
ADVERTISEMENTS:
9. Leaf traces of cycdales are multiple; some girdle stem.
10. Pith is well-developed in it.
11. Mucilage or resin canals of cycadales are in stems.
12. Same as in Lyginopteridaceae.
13. Pericycle indistinct in cycadales.
14. Cycadales is monoxylic in most of the genera and polyxylic in some (e.g. Cycas, Encephalartos).
15. Secondary xylem in cycadales are usually exocentric.
