231 
Pteridophytes , Are they vestigial? 
25. Z. verticillatum , Linn. fil. One of the least differentiated 
species, as regards sterile and fertile zones: there is no distinction 
between sterile leaves and sporophylls, while isolated sporangia are 
dotted here and there in the sterile region. In extreme cases there 
is no distinct fertile region at all, but only isolated sporangia among 
sterile leaves. 
2 r L. setaceum , Hamilt. | Alternating sterile and fertile zones. 
28. Z. mollicomum , Mart, j 
30. Z. affine , H. & G. 'j 
31. Z. Lindeni , Spring. > Alternating sterile and fertile zones. 
32. Z. attenuatum, Spring. J 
35. Z. Trencilla , Sodiro. This ‘giant of recent Lycopodiaceous 
types' shows, in the Kew specimens, sporangia down to its very base: 
there is no differentiated strobilus. 
( Alternating sterile and fertile zones, 
usually with a sterile region at the 
base : some isolated sporangia in the 
sterile regions. 
38. Z. dichotomum , Jacq. There is usually a long sterile basal 
region : the sterile and fertile leaves are alike ; the fertile zones are 
irregular : a few sterile leaves may intervene in a fertile zone, and 
isolated sporangia may be found in a sterile zone. At the limits 
abortive sporangia have been seen. 
39. Z. taxifolium , Swartz. There is a long sterile region at the 
base of the plant : above it alternating sterile and fertile zones : there 
is a tendency to fine off at the fertile apices, forming ill-defined terminal 
strobili, with smaller leaves: but the graduation is very slight and 
gentle. Mr. Baker notes for Z. passerinoides , H. B. K., the leaves that 
* subtend sporangia rather abbreviated.’ 
The above species constitute the sub-genus Selago , which 
includes mostly ground-growing plants : the characters are 
based on the sporangia being c placed in the axils of unaltered 
leaves all down the stem V The following are the most 
important points brought out in the above notes : — 
1. Most species have a sterile basal region of considerable 
length: but sporangia have been observed down to the base 
of the mature plant, in Z. compacium , and Trencilla , or close 
1 Baker, Fern- Allies, p. 8. 
