I12 EVANS—EFFECT OF ENVIRONMENT ON THE 
3 mm. even in arborescent forms, and being often much shorter 
than the external limits of the hypocotyl. My hope of finding a 
more gradual passage from root to shoot arrangement was thus 
not realised. 
SUMMARY. 
1. Under natural conditions the hypocotyl in the genus 
Luzula is actively concerned in raising the plumule of young 
seedlings to the surface of the soil, if the seeds have become 
buried. The fact that this elongation has not been noted in 
previous papers on the subject is probably due to the method 
usually employed in such observations—germination upon the 
surface of moist material such as cotton, blotting paper, &c. 
Under such conditions the hypocotyl remains unelongated. 
2. Seedlings grown at the surface, but in darkness, show a 
similarly elongated hypocotyl, the stimulus to elongation being 
probably lack of sufficient light. 
3. The amount of elongation always corresponds exactly to the 
depth of the sowing of the seed, 
4. Normally the epicotyl takes no part in the elongation, 
remaining quite unelongated when the hypocotyl may be as 
much as 3 in. long. 
5. The primary root and the hypocotyl are very short-lived, 
being early replaced by secondary roots arising just below 
the leaves. 
6. The stele of the elongated hypocotyl shows typical sym- 
metry of a diarch root. 
7. 1 have not observed similar phenomena in the genus 
Juncus. 
LITERATURE CITED. 
1. LAURENT, M. Recherches sur le Développement des Joncées. Ann. des Sci. 
Nat. Série 8., t. xix. 1904. 
2. BuCHENAN, F. Jeriencets | in Engler’s Pflanzenreich. 
3- SoravER, P. Handbuch der Pflanzenkrankheiten. Vol. i., pp. 110-112. 1905. 
4- Hitt, T.G. The Seedling Structure of certain Piperacee. New Phytologist. 
Vol. iii., No. 2. 1904. 
5- TANSLEY, A. G., and Thomas, E. N. Root Structure in the Central Cylinder 
of the Hypocotyl. New Phytologist. Vol. iii., No. 4. 1904. 
6. SARGANT, Miss E. A Theory of the Origin of Monocotyledones, founded on the 
Structure of their Seedlings. Annals of Botany, Vol. xvii., No. 65. 1903. 
