25 



about half of the length, and is perfectly flat, never convex as in 

 L. dilatata ; the rachis is more or less clothed with thin, almost 

 diaphanous, rounded or oval scales, terminating with a little point, 

 but not at all acuminated. The pinnae are rather distant; the 

 pinnules more or less deeply pinnatifid, and sometimes even almost 

 again pinnate, especially in the lower part of the large fronds. All of 

 the segments are deeply serrated, the serratures terminating in a 

 sharp point or mucro curving towards the apex of the pinnule. 

 The venation is somewhat complicated, a branch of the lateral vein 

 extending to each serrature: the sori being produced upon the 

 uppermost branch of each lobe, are opposite to the sinuses, and 

 form a line on each side of the midvein ; in luxuriant specimens 

 this arrangement is often disturbed by superdevelopment. Fruc- 

 tification is perfected on the earlier fronds in July, and on the 

 later in September. The sori are generally small, the indusium 

 persistent, reniform, flat, a little waved on the margin, but never 

 ciliated with glands. As the thecse expand, the clusters frequently 

 become confluent, especially where the plant occupies an exposed 

 situation. 



The ordinary compost, shade, and moisture, are the only requi- 

 sites for the successful cultivation of this fern. It will bear expo- 

 sure, if well supplied with water ; but, to obtain it in its beauty, 

 it must be screened from the direct rays of the sun : the mottled 

 and ever-shifting light and shade produced by the intervention ol 

 trees, is always favourable to the growth of this beautiful tribe of 

 plants, even of those species which in a natural state occupy the 

 most unsheltered habitats. Compared with some others, this, like 

 L. rigida and L. cristata, is not perhaps so remarkably ornamental 

 that it would be included in a selection for planting with a view to 

 effect, but its character is much improved by judicious appropriation 

 of a site sheltered from wind and sun. 



In retaining this as a species, I am by no means inten ding to decide 

 that it has any positive claim to be so considered. The diversity 

 in habit, outline, and division of the frond, and other anomalies, 

 so frequently met with in ferns the specific identity of which can- 

 not be questioned, forbid any such assumption ; but amidst the 

 uncertainty and difference of opinion that prevail respecting the 

 species of this and the following genus, Polystichum, it seems better 

 to retain a name that has been applied to a certain well-known 

 form like that before us, than to discard it altogether. In appoint- 

 ing the limits between species and varieties, our conclusions are too 

 frequently drawn from very partial or imperfect data. 



LASTREA DILATATA. Broad prickly-toothed Fern. TAB. XIII. 



Fronds arched, ovato-lanceolate, bipinnate : pinnules pinnatifid 



D 



