ADDENDA. 
OPUNTIA SUBULATA, Engelm. In the grounds of Mr. Thomas Hanbury at Mortola, near 
Mentone, the interesting Cactus which is well known in cultivation as Peirescia subulata, 
Muhlenpfordt, has bloomed this spring (February), and is now maturing its fruit, and through Mr. 
Hanbury’s kindness I have been enabled to examine fresh specimens ; these have fully convinced 
me of the necessity, long suspected, of removing the species from Peirescia to Opuntia. My atten- 
tion was first drawn to this by the observation that the spines of this plant have, at least when first 
developed, barbs toward their points, and barbed spines (and bristles) are a singular peculiarity of 
all the members of the genus Opuntia, and are not found in any other cactus. This is a curious 
instance where a vegetative character of apparently minor importance becomes so constant and so 
exclusive as to at once readily distinguish all the members of this large genus from any other cactus. 
The barbs in this species are, however, slight, and are apt to disappear in older spines, and the 
smaller bristly spines generally so abundant (and annoying) in most Opuntie are almost entirely 
absent in this species. Another, and the most essential character of the genus Opuntia, is found 
in the expansion of the funiculus, which envelops the ovulum, and finally forms the whitish bony 
covering of the seed, which, if it was softer, we should call an arillus. This I first discovered in our 
plant several years ago in an otherwise incomplete specimen, kindly sent by Professor Todaro, of 
Palermo, and I find it so again in the flower now under inspection. This character is peculiar to all 
Opuntias, and is not seen in any other cactus. Peirescia, on the other hand, has the smooth spines 
and the dark-colored, mostly black, crustaceous seeds (destitute of a bony arillus) of all other Cac- 
tacee. The leaves, being somewhat persistent in O. swbulata, have probably been the cause of the 
plant having been referred to Peirescia before flower or fruit were known, but more or less persistent 
leaves are of not rare oceurrence in allied Opuntia, which on this ground have sometimes been 
referred to Peirescia ; subulate leaves have thus far not been found in any true Peirescia. In this 
species they are the largest of any Opuntia known, 3 to 5 inches in length. 
The narrowly pyriform ovary of O. subulata is about 3 inches long, and is covered with some- 
thing like twenty obcordate or rhombo-obcordate depressed tubercles, which bear in the notch a 
grayish woolly areola, rarely with a few bristles, and under it the thick, subulate, suberect, at last 
deciduous leaves (outer sepals) 14 to 2 inches long. About eight small dirty purplish petals, 
obovate to orbicular, very obtuse, form the corolla; and a few similar but acute sepals make the 
transition to the calyx. The slender style has about five branches. The only fruit seen was pear- 
shaped, 4 inches long and 2} inches thick ; the obcordate tubercles still showed their contour quite 
distinctly in 8; order, but were entirely flat; a few of the upper short sepals were still attached ; 
umbilicus narrow and very deep; eighteen very large seeds were found densely packed in the 
centre. The seeds were altogether the largest Opwntia seeds and. probably the largest cactus seeds, 
seen by me, 5 to 6 lines in the longest diameter, and 3 to 4 or even 5 lines thick, of irregularly 
angled shape and not flat as Opuntia seeds commonly are. A very narrow commissure, the external 
