ia ts eye ee ey 
OBSERVATIONS ON LESSONIA 321 
This is the explanation given by Areschoug' of the leaves of 
Léssonia nigrescens Bory. In Lessonia fuscescens Bory the older 
eaves are two-horned at the apex,this being caused by the carry- 
ing away of the upper part when decayed, as described by 
Hooker and Harvey.? In this species the sorus itself falls away 
from the frond and the old leaves must present a very different 
appearance from the younger ones. In Lessonia littoralis the 
_ latger leaves have lost their tips, but this does not seem to be 
due to a sloughing off of the sori, since the position of the 
latter is basal. The position of the two kinds of leaves in the 
in th 
species under consideration makes it somewhat difficult to 
believe that their difference is purely a matter of age. Unfortu- 
nately young material is not at hand, and this, as well as a large 
umber of other interesting questions, must be held in abeyance. 
tis true that the sporophylls are more coriaceous than the 
-Sknder sterile leaves, and as will appear in the histolological 
portion of this paper the general structure of the sporophyll 
. neatly equivalent to that of the midrib in sterile leaves. 
Nevertheless, from the very constant position of the leaves upon 
the ultimate branches of the stipe, it is difficult to assign them 
different ages unless some modification of the ordinary devel- 
pment by basal splitting has arisen. Indeed some evidence e 
» May be derived from the specimen under observation, in 
Which very often but a single lamina of the narrow form appears 
“Notch between two of the broad laminae, and in a a 
stances the single central lamina is split at the base, thus giv- 
= tWo petioles. It is therefore possible to conceive how by 
the continued Srowth of the plant the pair of leaves of one year 
: . ‘eparated by the pair of the succeeding year. This 
a Very much as described for Lessonia nigrescens by 
Ateschoy 
+. 18 in the work cited, and it may be said also of Lo 
alis with tolerable certainty that there is a ‘true defoliation 
4 true foliation.” 
fall laminae at the end of a branch could be regarded as 4 
oe Observ. Phyc. 5:8. 1884. 
00K 
ER and HARVEY: Flora Antarctica 2:457. 1847. 
