248 ALPINES AND BOG-PLANTS 
in the rock-work. Lastraea thelypteris is a larger, rather 
uninteresting fern for the bog ; Lastraea oreopteris is stift 
and stark in its upright growth, from open, heathy banks 
on the fells. Lastraea rigida, if one could get it, 
has the attraction of extreme rarity, and still lurks 
undiscovered among the common Lady- ferns on the 
upper slopes of Ingleborough, whence it was first 
recorded. On the same slope occurs the Parsley Fern—a 
mere caricature of itself as it luxuriates on the slates and 
primary formations of the Welsh mountains. But 
though I have seen Allosorus crispus making stout bushes 
by the stream-sides that flow down to Llyn Idwal, I have 
had so uniformly disheartening an experience with this 
fern on my limy soil, that I will not give it any recom- 
mendation for the bog. 
Finally comes the one grass that is really of prime 
value for the rock-garden and the bog (not mentioning 
Festuca varia, beautiful neat cushion of finest emerald 
fur, even in midwinter). Poa alpina is indistinguishable 
in growth from the tufts of any common grass that one 
rends up as a weed. But in its viviparous form the plant 
produces rich heavy masses of living baby plants, the 
whole blossom-head being a great tassel of plumy emerald 
touched with crimson. Beneath their load the frail stems 
bend earthward, and there in due time deposit their load, 
each sprouting bulblet producing a young plant. Poa 
alpina vivipara is quite common in the Alps, and occurs 
very rarely in the Highlands and in western Ireland— 
notably on one mountain overhanging the sea. In 
cultivation it is perfectly easy and robust, thriving in any 
rich, damp loam. Its only drawback is its very close 
resemblance, while out of flower, to its common cousins, 
which often causes Poa alpina to be weeded up, while the 
real weed next door is left untouched. 
In dry clefts of every wall in the Ligurian vineyards 
