Lastrea. 
149 
intervals. The fronds are of two kinds ; the barren ones, which are developed about May 
or early in June, are usually from one to two feet high, although often much smaller, 
smooth or slightly hairy, the lower pair of pinnae being a little, but only a little, shorter 
than those above them. The barren fronds have narrower pinnae, this difference in appear- 
ance, which is easily recognisable, being due in no small degree to the incurving of the 
margins over the sori. The stipes in the fertile fronds, 
which is developed a month or more later than the barren 
ones, is longer in proportion, and the whole frond is taller 
and stouter. The small round sori are produced in large 
numbers upon the back of the frond, being situated near 
the base of the venules, as shown in the figure ; these 
venules proceed from the central vein, or midrib, becoming 
forked, and terminating at the margin of the pinna. The 
accompanying figures — which are of the natural size — will 
show the difference in form between the barren and the 
fertile pinnules. 
This species is by amateurs sometimes confused with 
the next, L. Oreoptcris, but is very easily distinguished 
from it, not only by its slender creeping rootstock, but 
by the form of the fronds, the pinnules of which, in L. 
Oreoptcris, become gradually smaller towards the base ; L. 
Thelypteris is also quite destitute of the pleasant balsamic 
odour which characterises L. Oreoptcris. It is widely 
distributed throughout northern and central Europe, but 
becomes rarer towards the south ; it is absent from the 
Spanish peninsula, and is rare in Italy. In northern Asia 
it occurs in Amur-land and Mandschuria ; in northern India 
it is reported from Khasia and Kashmir, at an elevation 
of from five to six thousand feet. It is found also in New 
Zealand ; and in Africa it is reported from Angola, Cape 
Colony, and Natal. It is common in Canada, and extends 
throughout the United States to Florida. 
Lastrea Thelypteris is known in books as the Marsh 
Fern ; in the Isle of Wight it is called Ground Fern, but, 
like many more of its class, it has no generally recognised 
English name. Its specific name is a Greek compound, 
signifying Lady kern, and was probably originally (*) pinnule of fertile frond. 
bestowed upon the plant on account of its delicate appear- 
ance. It is not a difficult plant to grow, but requires a very great quantity of moisture ; 
indeed, it is cultivated to the greatest advantage in the neighbourhood of water, as on the 
boggy margin of a small pond, if such a situation can be obtained for it. The fronds are 
annual, and are cut off by the early frosts. It is not at all a variable plant. Milde dis- 
tinguishes two forms, one of which has the segments of the pinnae deeply and irregularly 
pinnatifid, while in the other the fronds are somewhat glandular; but no marked deviation 
from the type exists. 
