10 THE WEEDS OF NEW SOUTH WALES. 



2. Weeds with silky hairs. 

 These may be in three forms. 



(a) Fruits with a pappus or parachute arrangement, as with so many of 

 the Thistle or Daisy family (Composite). A good example is the Thistle. 

 The seeds of thistles go sailing along like shuttlecocks. 



(fr) The carpels may terminate in long silky tails as in the Clematis, a 

 white-flowering climber which adorns the bush. A pui! of air sends them 

 flying. 



(c) Hairs may cover the seed, as in the case of the true Cotton plant 

 (Gossypium) , or Cape Weed (Cryptostemma}. These seeds are not so light 

 and feathery as those in (1) and (2). Still, the cottony hairs catch the breeze 

 and facilitate the transport of the seeds to congenial soil. 



3. Weeds with wing-structure. 



We have what I may term the wing or aeroplane structure. This is 

 readily recognised in the case of Pines, She-oaks, and a surprising number 

 of our native plants. Sometimes the wing encircles the seed; sometimes the 

 wing is at one end of a seed. In the case of a pine, for example, the ripe 

 cone opens and the wing, weighted or balanced by the more solid seed, floats 

 away to its destination,, lazily if the air be still, but, if there be a fresh wind,. 

 a surprising distance. 



4. Weeds with " tumble-weed " structure. 



The entire panicle breaks off near the base of the culms and rolls over the 

 ground, its progress being facilitated by the horizontal spreading branches, 

 which act as sails. 



We have this in grasses. For instance, the inflorescence of the common 

 grass Deyeuxia Forsteri, breaks off and is rolled about by the wind. The 

 Windmill grasses move about in the same way, and very often we notice 

 how they accumulate in the corner of a paddock, sometimes overtopping 

 the fence, and blowing over into the next paddock. Sometimes the grasses 

 are carried along the railway-line, and the rush of the train keeps them in 

 active motion. Standing on the Sydney Station I have often seen the 

 inflorescence of grasses in front of the engine which must have been carried 

 along for many miles. 



Some plants are called " Roly-Poly " in Australia because of this tendency 

 to take on this tumble-weed character. Salsola Kali is an example. 



Weeds Distributed by Floods. 



Floods bring down seeds good and bad, generally bad, and deposit them 

 in nice moist alluvial soil under conditions very favourable to germination. 



In our own State it is notorious that the Prickly or Mexican Poppy 

 'Argemone mexicana) and the Noogoora Burr (Xantliium strumarium) are 

 transported and propagated in this way. 



Sling Fruits. 



Such include the pods of Leguminosse (the Pea, &c., family). 

 The mechanism by which the seed of the common Broom ( Ulex europceus} 

 is propelled some distance was described as far back as the year 1546. 



