346 LYCOPODIALES 
to its base: it is clear that the relation of the apex to the intersection of 
the first walls has been a close one (Fig. 183 4). The axis soon proceeds 
to form successive leaves spirally arranged. The cotyledon and subsequent 
leaves have the ordinary characters of the foliage leaves of the species. 
The tissue below soon becomes elongated as the hypocotyl, the length of 
which is determined by the level at which the prothallus lies in the soil: 
where it is at or near to the surface the hypocotyl may be quite short: 
where deeply seated it lengthens, so that the first leaves are exposed 
above ground (Fig. 184). It is 
traversed by a vascular strand, 
which is monarch below, but 
near to the first leaf, or later, it 
becomes diarch, and shows two 
lateral tracheidal strands. The 
first root originates exogenously 
from the upper tier, just above 
the foot, and is succeeded by 
other roots of endogenous origin 
at higher points (Fig. 183. B). 
Here, then, is an embryogeny 
characterised by its great direct- 
ness and simplicity. The only 
complication is the varying elon- 
RAKNG ae . 9 Olea eae 
\\ ANS : to t e evel of t epee allus in 
RS the soil; and there is good reason 
to think that this is an immediate 
Fic. 183. adaptation to meet the varying 
Lycopodium Selago. A=yotng embryo. x150. levels of development of the game- 
#=foot; 1V.-IV.=wall separating the foot from the Bs + es 
stem-tier; AK=cotyledon; @=apex; #f=suspensor. tophyte in the soil, in an embryo 
base of the axis. x 20. (After Brachaianti) pep ine Oe NUESINE of the embryo by the 
prothallus is not long continued, 
nor is it structurally provided for, there being no development of an 
elaborate ‘*calyptra,” as in some other species: the embryo soon escapes 
from the prothallus, and fends for itself. The whole condition of the 
embryo is such as bespeaks a simple and primitive state. Probably this 
view would never have been in doubt had it not been for the existence of 
different arrangements seen in other species of the genus, which happened 
to have been described some years earlier. 
Of these the type which corresponds most nearly to Z. Se/ago-is that 
of LZ. Phiegmaria, so accurately described by Treub.1 Here the segmen- 
tation of the embryo, as well as the origin of all the parts and their 
proportions while young, have been fully made out, and appear to be 
1 Ann. Jard. Bot. de Buitenzorg, vol. v., p. 87, etc. 
