236 Bower . — Imperfect Sporangia in certain 
Group of L. cernuum . 
In the cernuum group of ground-growing species the strobili 
are clearly defined. Transitions from the strobilus back to 
the vegetative shoot are decidedly rare : none were observed 
in L. cernuum itself, in a very large number of specimens: 
a slight indication of it was seen in L. obscurum , but none in 
L . casuarinioides . 
Group of Z. clavatum. 
These are all terrestrial, with trailing habit, and ascending 
branches, which bear well-defined strobili : reversions from 
strobilus to vegetative shoot have not been observed. A com- 
parison of the species illustrates the way in which the strobilus 
may have come to be lifted on a long pedicel above the ground, 
with the result of a better dissemination of the spores : this is 
shown by the following notes. 
76. Z. Sprucei , Baker. This species having solitary spikes sessile 
on leafy branches, connects the group with Z. inundatum. 
77. Z. magellanicum , Sw., has also spikes ‘ sessile or nearly so/ and 
‘ often many to the branch/ as in Z. clavatum. 
80. Z. annotinum , L. The leaves at the base of the strobilus are 
frequently smaller than either foliagq leaves or sporophylls, but they 
occupy no specially elongated zone : the leafy branches, which rise 
from the creeping rhizome and bear the strobili, attain a height 
of six inches. 
78. Z. contiguum, Klotzsch. The zone may be a quarter of an 
inch in length : the strobilus simple or sometimes branched. 
81. Z. diaphanum , Sw., has a considerable zone of narrower linear 
leaves between the strobilus and the larger foliage leaves. The 
strobilus is simple or branched. 
84. Z. clavatum , L., has an elongated stalk, of length varying from 
two to six inches, covered with distant appressed scales, i. e. the axis 
has lengthened, and the scales are correlatively reduced. Z. arista- 
turn, , H. B. K., is a form with specially elongated stalk, and several 
spikes. 
86. Z. paniculatum , Desv. The stalk, nearly a foot long, may arise 
direct from the rhizome, and bears many branched spikes. 
