232 Bower . — Imperfect Sporangia in certain 
to the base in others, e. g. Z. fir mum and rigidum . There are, 
however, no records for young states of these species. 
2. The sterile and fertile zones are imperfectly differentiated : 
this is illustrated by all the species. 
3. The sterile and fertile leaves are mostly alike : and though 
the fertile leaves show in some cases a smaller average size than 
the sterile (Z. serratum ), this is not constantly the case even in 
that species. 
4. Isolated sporangia have been frequently found in the other- 
wise sterile region, in the axils of leaves resembling the sterile 
leaves in size (Z. Selago, Hamiltonii , reflexum , miniatum , ceylani- 
cum , lucidulum , myrsinites, verticillatum , setaceum, mollicomum , 
sarmentosum, linifolium , dichotomum). 
5. Sterile leaves have been found in the fertile zone (Z. dicho - 
tomum). 
6. Incompletely developed sporangia have been found at the 
limits of the fertile zones in Z. Selago, and dichotomum : this is 
not readily observed in herbarium specimens, and most of the 
species have only been available in the dry state. 
It is clear from these facts that the fertile and sterile 
regions are, in the sub-genus Selago , very imperfectly differ- 
entiated, a conclusion which has important bearings on any 
view as to the evolution of the genus. 
Sub-genus II. Sub-Selago. 
42. Z. carinatum , Desv. The foliage leaves graduate by gentle 
steps to the sporophylls : the spike is terminal but not distinctly 
defined, and the lower limit of sporangia is not sharply marked. 
Straggling sporangia, and sporangia of smaller size, i. e. partially 
abortive, are found at the base of the spike. Occasional reversions 
from the strobilus to the sterile state have been seen in this species, 
a condition similar to that in the Selago group. 
45. Z. gnidioides , L. fil. The delimitation of the strobilus in this 
species is by no means exact : interruptions of the fertile zone occur 
at the base, and isolated sporangia are frequent, irregularly scattered 
in the sterile region below. The strobili often resume a vegetative 
condition at the apex. 
