94 



hood of St. John's and in other parts of the 

 island. It causes the plant affected to become 

 stunted in habit, and indeed parts may perish, 

 brown spots with zoned markings gradually 

 covering the entire green surface of all parts of 

 the plants victimised, and so interfering with 

 iinportant functional activities. 



As it does not appear to have been generally 

 noticed, some account of its outward features 

 may be given. It commences with the develop- 

 ment of small, slight raised, sub-circular spots, 

 each 2-3 millimetres in diameter, havine a pale- 

 brownish colour with a distinct nucleus of a 

 darker hue. These spots increase in size and 

 meanwhile lose their circular outline, their mar- 

 gins, however, maintaining an irregularly waved 

 pattern. They are now from 5 to 10 mm. in dia- 

 meter and are better defined on the general ereen 

 stem-joint surface than previously, having be- 

 come buff-coloured, resembling blotches of yellow- 

 ish-white paint. They are usually bordered by 

 a paler and more translucent encircling zone, indi- 

 cating the fact of their gradual extension to form 

 larger spots. Meanwhile, innumerable greyish- 

 black, densely distributed points have appeared, 

 these being arranged in lines or bands running 

 one within the other, following the outline of the 

 spot — Whence the term "zone-spot." These spots 

 often merge, but their general concentric 

 character and independent origin are always 

 manifest. 



The points when viewed under the lens are 

 seen to be short, racemose, grey-coloured, raised 

 figures, with minute linear fissures exposing a 

 blackened interior, evidently indicative of fungus 

 growth. They occupy the affected surface with 

 less or greater completeness, according no doubt 

 to the time that has elapsed since the spot 

 originated. Meanwhile these zone-spots become 

 larger and larger until they may attain indi- 

 vidually a diameter of 5 centimetres or even more, 

 their dark, striated appearance being now very 

 noticeable. Usually, before the dimensions stated 

 have been attained, neighbouring spots have 

 coalesced, but the separate origin of adjoining 

 spots is, however, still shown in those that have 

 become so confounded. Thus a larger and larger 

 area of the stem- joint may be involved, until this 

 may be outwardly wholly affected, more or less 

 numerous originally isolated spots contributing 

 to this result in different cladodia. 



With regard to the effects produced where 

 these spots occur, the epidermis of the stem-joint 

 often dies, and so the surface implicated may 

 become fissured. For a while the segment which 

 has been attacked remains alive, but under some 

 circumstances — perhaps rainy weather — evidently 

 often realised, gradually dies, becomes decayed 

 internally, and ultimately dries up, there being 

 left a mere shell, still exhibiting the original 

 surface areas of fungus, growth. 



This peculiar disease, which occurs also on 

 other "West Indian islands as will be subsequently 

 seen, was found to occur exclusively on 0. dil- 

 lenii, even when related kinds of prickly-pear 

 were growing adjacent to affected individuals of 

 this species. 



No natural enemy was observed in associa- 

 tion with the low-growing 0. triacantha, but, 

 many cactus areas on the island having remained 



imvisited by the Commission, it cannot safely be 

 concluded that this plant everywhere maintained 

 tliis healthy character. The remark applies also 

 to other Antiguan species of Opuntia. 



ST. KITTS. 



On this island the high and rugged unculti- 

 vated country to the south of Basse Terre was 

 examined, and the road along the foreshore all 

 around the island traversed. In the rocky and 

 dry brush-clad situations, prickly-pear (0. dil- 

 lenii and 0. triacantha) was very plentiful, being 

 sufficiently dense in some places to impede one's 

 progress. Along the seaboard outside the agri- 

 cultural land, apparently only the former of these 

 species occurred, and then grew sometimes in 

 clumps but more commonly as isolated plants. 



The Agricultural Superintendent, Mr. F. E. 

 Shepherd, stated that the prickly-pear could never 

 obtain any hold in the agricultural areas as it 

 was the custom to extirpate and burn it, and 

 on certain lands where no cultivation had been 

 carried on it apparently was choked out by other 

 vegetation. He also stated that, although he had 

 not paid close attention to the local Opuntias, 

 no natural enemy affecting the plant had come 

 under his notice— not even the cochineal insect. 



The only disease noticed on this island was 

 the Zone-spot Disease occurring sparingly on 0. 

 dillenii, and the White Diaspis Scale of Cacta- 

 ceous plants. 



NEVIS. 



On visiting this island the more or less bar- 

 ren area along the new road, that extended for 

 some miles, was examined; also the interior 

 between the town and Gingerlands. The circuit 

 of the island by the coast road was also made. 



The kinds of pricMy-pear endemic on Nevis 

 are (1) 0. dillenii, (2) 0. triacantha, and (3) a 

 peculiar hybrid combining the characters of these 

 two, of which specimens had been pointed out to 

 us in the New York Botanic Gardens by Dr. 

 Britton, who, in company with Dr. Rose, discov- 

 ered the hybrids on St. Kitts. 



(4.) In addition, Nopalea cochinelifera was 

 met with as a garden plant. The first two of 

 these Opuntias grew in abundance, especially to 

 the west of the town and in much of the arid and 

 barren country traversed by the new road. 



As bearing on the question as to whether 

 prickly-pear plants have always been a compo- 

 nent of the island's flora, or whether they were 

 introduced at some remote period, it may be men- 

 tioned that whereas Smith, in his ' ' Natural His- 

 tory of Nevis," printed in 1745, makes mention 

 of several other plants, he omits all reference to 

 such curious members of the vegetable world as 

 are the Opuntias. 



Disease Occurrence. 

 Plants of 0. dillenii were commonly affected 

 by the Zone-spot Disease, and the action of the 

 latter in rendering its host-plant stunted with a 

 great arrest of growth was very noticeable, 

 especially along the roadside in approaching 

 Gingerlands. 



