HYPOCOTYL IN THE GENUS LUZULA. 109 
or less buried before germination—which is often long delayed 
amongst luzulas—commences. A means of bringing the leaves 
of the seedling above the material covering the seed would 
give the young plant a much more favourable start in its 
ife 
Apparently, under ordinary conditions, the internodes of the 
stem itself take no part in the work performed by the hypocotyl, 
but remain quite as short as in a surface-grown seedling. The 
possibility of their elongating if necessary is, however, hinted at 
by the fact that one of my seedlings of L. maxima, DC., germin- 
ated below ground, showed the first internode of the shoot 
elongated as well as the hypocotyl (Fig. 3). | Why this seedling 
should have developed in this exceptional way I am unable to 
explain, as the seed was no more deeply covered by the soil than 
any of the others,.and the internode between the base of the 
cotyledon and the first foliage leaf projected entirely above the 
earth. According to Sorauer (3), two internodes (apparently the 
so-called mesocotyl and the first internode of the stem) take part 
in bringing to the vicinity of the surface the leaves of too deeply 
sown rye seedlings. In surface-sown plants these two internodes 
remain contracted and closely superposed. 
An experiment was made to test the effect upon the hypocotyl 
of lack of sufficient light at the time of germination. A surface 
sowing was made of seed of L. campestris, DC., and the pots of 
soil placed in almost complete darkness. |The seed germinated 
readily, and, as I had expected, the hypocotyl became elongated 
in the same way as before, though to a rather less extent. 
longitudinal section through the median plane of one of these 
seedlings is shown in Fig. 8, the drawing being, unfortunately, 
in part diagramatic, owing to the large cortical cells having 
become much crushed in the process of embedding in paraffin. 
It is probable, then, that lack of light is the chief stimulus 
in causing the elongation of the hypocotyl in seedlings of 
Luzula, which would hardly ever be so deeply buried in the 
soil as the rye seedlings mentioned by Sorauer (3), who 
attributed the elongation in their case to a need for better 
aeration. 
I have not been able to observe any phenomena such as those 
described above in the genus Juncus. 
