BEAUTIFUL FERNS. 
15 
monly there is but one fruit-dot to a lobe, but sometimes 
there are two on the upper side, and rarely a third on the 
lower. The involucre is like a little cup, and is formed partly 
from the reflexed tip of the fertile tooth or lobule, and partly 
of a special true involucre, which meets the other part and is 
united with it. Inside the cup are found about a dozen spo- 
rangia, which have from twenty to twenty-four articulations 
in the ring. The spores are trigonous with somewhat im- 
pressed sides, and three faint vittas along the angles. 
There has been a great deal of confusion respecting the 
names of this fern, both generic and specific. The genus 
Dicksonia was proposed by L’Heritier in 1788 for two species, 
D. Culcita of the Azores and Madeira, and D. arborescens of 
St. Helena. In these the involucre is very distinctly two- 
valved, the outer valve formed from the apex of a lobe. About 
a dozen other species are now known, which are plainly con- 
geners of these two. In 1801, Bernhardi proposed a genus 
Dennstc€dtia for the Trichomanes Jlaccidum of Forster, a fern 
much more like our own, and, like it, having a cup-like, and 
not two-valved, involucre. But the proposed genus was 
promptly rejected by Swartz, Schkuhr and Willdenow, and 
the plant referred to Dicksonia, which by 1810 was made 
the recipient of as many as twenty species. Since then Sit- 
obolimn (or Sifolobium), Patania and Adectum have been 
proposed for some of these species with cup-like involucres. 
Some of these names have met with a limited acceptance, 
but all were rejected by Hooker. The authors of Species 
