80 



near East London, Port Alfred, Alexandria, 

 Albany, Bathurst, Port Elizabeth, Grahamstown, 

 King Williamstown, Uitenliage, Humansdorp, 

 and Hankey, the valley of the Gamtoos River, 

 Fort Beaufort district, Capetown, Stellenbosch, 

 Paarl, and Malmesbury. 



Macdonald's "Doornblad" (1897 a, p. 28), 

 with spines two inches long, from Addo and 

 Grahamstown, is evidently this species. He men- 

 tions (p. 29) the occurrence of the Cochineal 

 Insect on the form with small " leaves" and 

 long spines. 



Opuntia decdmana. — The history of the 

 introduction of the Prickly-pear into South 

 Africa is briefly given by MacOwan (1891) and 

 by Macdonald (1891 a, p. 21), who stated that 

 it was brought via India by Dutch East India- 

 men. 



The Western Province of Cape Colony was 

 first invaded, the pear becoming spread east- 

 wards by human agency. Thunberg, in his work 

 published in 1823, recorded its presence; and 

 Sparrman found a cactus, which appears to have 

 been the pest pear, in the Sneeuberg in 1776. 

 Macdonald (1891 a, p. 21) has traced the in- 

 troduction of the pest in 1750 from Capetown to 

 Buffiels Hoek, and a little later from this place 

 to the Pearston district, which has now become 

 the centre of a densely-covered area. The slow 

 progress of the invasion is no doubt accountable 

 for the fact that Drege has not included this 

 cactus amongst his list of plants found in the 

 locality between 1826-1834 {see Bolus " Flora of 

 South Africa," 1886, p. 23). In 1847 the pear 

 had established itself in the Cookhouse and 

 Somerset East districts (R.S.C., 1898, p. 19), 

 whence it gradually spread. 



It has already been mentioned that a great 

 deal of confusion has arisen regarding the name 

 of this pest pear (0. decumana) of South Africa. 

 In that country it has been called 0. vulgaris 

 (Grobelaar, 1891; MacOwan, 1881), 0. tutm, 0. 

 triacantha, 0. decumana, and 0. cochineUfera. 

 It is usually known under the names of its two 

 more or less well-marked varieties — Doornblad or 

 " thorny-leaved " pear, and Kaalblad or 

 " smooth-leaved " pear. There seems now to be 

 little doubt that the two forms belong to the same 

 species, as it is not a difScult matter to obtain 

 a series in which the specimens may be ranged 

 in such a way that one passes from the typical 

 Doornblad to the Kaalblad, Intermediate forms 

 are quite common. 



A good description of the two varieties of 0. 

 decumana was given by Dr. Marloth in his report 

 on "The Prickly-pears of South Africa" (1892 

 b, pp. 19-20), where the species is regarded as 

 0. tuna or 0. ficus-indica. Both names are held 

 to belong to the same plant, but on account of the 

 confusion of names he has adopted the former 

 (R.S.C., 1906, pp. 22-3). He also referred to 

 some well-marked variations which may be met 

 with, all of which have also come under the notice 

 of the Commission. For a long time the Kaalblad 

 and the Doornblad were held to be distinct, 

 though the possibility of hybridisation was recog- 

 nised. "With a view to settling the question, 

 which, as will be seen later, was one of much 

 importance in the matter of destruction, experi- 

 ments were suggested by Dr. Marloth and 

 carried out by the Department of Agriculture 

 (Nobbs, R.S.C., 1906, p. 89 ; Fischer, 1892, p. 18 ; 



Marloth, 1906, p. 16). There is now little doubt 

 but that the thorny variety or Doornblad is 

 simply a reversion from the cultivated Kaalblad 

 or " smooth-leaved " form. 



The two kinds differ in a few particulars. 

 In the latter instance, sometimes spoken of by 

 Dutch farmers as the female Prickly-pear 

 (wyfetje), the joints are less sweet, but rather 

 thicker, more succulent, and less spiny, and 

 may in large plants be spineless. The fruit 

 is stated to be rather less sweet and less spiny, 

 but somewhat larger. The general appearance 

 of the plant and the flowers is similar. The 

 young joints of both varieties are equally spiny, 

 but as they mature, the spines persist in the 

 case of the Doornblad (the mannetje or male 

 Pear of the Dutch farmers), while they become 

 more or less aborted in the case of the Kaalblad. 

 The flowers vary from yellow to orange in both, 

 the usual colour being orange. The Kaalblad is 

 generally restricted to the rich soils found in 

 valleys, while the Doornblad thrives just as well 

 amongst the rocky hills as in those. 



Wallace (1896, p. 90) recognised that the 

 Kaalblad was the true Cochineal Cactus, and men- 

 tioned that specimens of the insect might be 

 seen living on it in the Botanical Gardens at 

 Capetown. 



Distribution. — In regard to the agencies 

 which are at work in distributing this species in 

 South Africa, undoubtedly the chief is man. Be- 

 fore the seriousness of the introduction was 

 realised, farmers commonly took joints from one 

 centre and planted them in another. Then, 

 again, the fruits being edible and abundantj 

 they have formed an important article of diet 

 for natives and for the " poor white" popula- 

 tion, and as a result the seeds have become dis- 

 tributed in the excreta. Cattle, birds, goats, 

 horses, pigs, baboons, &c., are responsible for 

 much of the distribution.* Though ostriches are 

 fed at times on the joints and fruit of this cactus, 

 they are probably not responsible for spreading 

 the pest by means of the seed in their excreta, 

 owing to the pulverisation of the contents of the 

 digestive tract of the bird. Rivers have also 

 assisted in scattering the pest pear. Then, 

 again, the Boer hereditary system (R.S.C., 1906, 

 p. 55; Macdonald, 1891, b, p. 27; 1897, a, 

 p. 31) has been partly responsible for the neglect 

 M'hich has allowed the weed to obtain such a 

 strong foothold. 



In regard to the distribution of the pest 

 pear, there is an area in the Karoo, in the 

 Eastern Province of Cape Colony, where 0. 

 decumana has spread to such an extent as to 

 constitute a very serious pest, to which public 

 attention has been called on many occasions 

 (R.S.C., 1890, 1891, 1898, 1906). This area 

 ranges from about 1,000 feet to 4,500 feet in 

 height, receives a low annual rainfall, and pos- 

 sesses a soil rich in lime. Though this species is 

 widely spread in South Africa, it has not proved 

 itself a pest except in certain regions. 



It occurs abundantly in the following dis- 

 tricts in Cape Colony: — Graaffi Reinet, 

 Aberdeen, Pearston, Willowmere, Jan- 

 senville, Humansdorp and Hankey, 



* The weight of evidence in regard to the germina- 

 tion of the seed appears to be in favour of the conclusion 

 that it is hastened by the passage through the alimentary 

 canal of a bird or manunal. 



