233 
Pteridophytes. Are they vestigial? 
In some Madagascan forms of this species there is a basal rosette 
of larger foliage leaves, from which springs at once the rather definite — 
branched strobilus condition, suggesting a comparison with Phyllo- 
glossum. 
4 6. L. dacrydioides , Baker. The basal limit of the strobilus is ill- 
defined. 
47. Z. squarrosum , Forst. There is a specialization of the strobilus 
from below upward, as shown by the very gradual decrease in size of 
the sporophylls : at the base these equal the sterile leaves in size. 
The base of the fertile zone is not always sharply limited ; occasionally 
isolated sporangia may be found below, in the sterile zone. 
49. Z. Dalhousiaeanum , Spring. There is a considerable difference 
between foliage leaves and sporophylls, but the transition is gradual : 
sporangia appear first on the transitional leaves, about half-way between 
the two types. The strobili are apt to be interrupted by sterile zones, 
where however the leaves remain small. 
The sub-genus Sub-Selago , introduced by Baker into 
Spring’s system, shows the sterile leaves ‘a little different 
from the bracts, but passing into them gradually. Sporangia 
aggregated into indistinct terminal spikes.’ The few species 
thus grouped show many of the characters of Selago. All 
have a basal sterile region, but recurrence of sterile and fertile 
zones is rare, though occasionally seen (Z. Dalhousiaeanum ) : 
reversion from the fertile strobilus to a sterile state is more 
frequent (Z. carinatum, gnidioides). The progressive diminu- 
tion of size of the fertile leaves upwards is sometimes gradual 
(Z. squarrosum ); this was already indicated in Z. taxifolium , 
in the Selago group: it is sometimes more sudden {L. Dal- 
housiaeanum). Isolated sporangia in the sterile region are 
more rare, but do occur (Z. carinatum, gnidioides, squarro- 
sum)'. also partially abortive sporangia at the base of the 
strobilus (Z. carinatum). Thus all the characters together 
show a very close similarity to what is seen in the Selago 
group, but with gradually increasing definition of the strobilus 
from the lower vegetative region. 
