ic)2 PLATE 47 



Fam. 1 6. Polygonaceae. 



The genus Polygonum is represented in South Africa by several introduced 

 as well as indigenous species. Among the former is the ubiquitous Pulxgonuni 

 aviculare (knotweed, Varken8gra8), which readily invades gardens and roads. 

 It is able to thrive in the driest situations where almost all other plants perish, 

 except perhaps Alternanthera Achyrantha t tor like this American intruder it 

 produces a very long tap root, which even in young plants, hardly a few weeks 

 old, may measure 12 inches or more, while in old plants it descends to two or 

 three feet. These plants are thus enabled to obtain their water supply from 

 the deep-seated moisture and to flourish in the driest summer. 



Polygonum serrulatum [Duiz&ndktWOp) is tairly trequent along all perennial 

 rivers of the country and easily recognised by the serrate edges of its Leaves. 

 Otherwise it is somewhat similar to the introduced weed P. Persicaria. 



Fam. 19. Nyctaginaceae. 



BoERHAAVIA # . 



All species possess a stout, deep-seated rootstock (big. 85), from which 

 several branches rise to the surface of the ground. From them originate the 

 thin trailing shoots which appear at the beginning of summer when the rains 

 have soaked the soil. The largest species is Boerhaavia petitioning which 

 spreads on the ground or ascends in bushes, the shoots being three or more 

 feet long. The flowers stand in umbel-like racemes and are bright coloured 

 but very fugacious. The coloured part is not a corolla, but the limb of the 

 simple perianth, while the persistent basal portion acts as a protection for 

 the fruit and assists in its distribution. Being provided with numerous viscid 

 knobs it is easily detached by passing animals and thus carried away. 



Farmers look upon it as a good food for stock. 



Phaeoptilum spinosum. This is a rigid, spiny shrub, 2 to 3 feet high, very 

 conspicuous when bearing its numerous, mostly bright red fruits. Neither 

 when in flower nor when fruiting would one at first "lance recognise its 

 relationship to Boerlunivia or Bougainville^ for the cream-coloured flowers 

 look, if not examined in detail, almost like those of some species of Lyduw, 

 and the four-winged fruits resemble those of some Combrctaccac. 



The shrub is recorded from Calvinia, and we have seen it on the Asbestos 

 Hills near Griquatown as well as in the mountainous parts of Great Namaqua- 

 land. 



* Named after Herm. Boerhaave, a famous physician and professor of botany at 

 Leiden, 1668 — 1 738. The city of Leiden erected a monument in his honour with his 

 favourite motto: 



u Simplex sigillum veri." 



