THE WEEDS OF NEW SOUTH WALES. 



2. Plants which are indigestible, and therefore injurious. 



In this section we have two plants which are typical of many others. The 

 first is the "Bean Tree" or " Moreton Bay Chestnut" (Castanospermum 

 australe), a pride of our Northern rivers, but frequently ringed by stock- 

 owners because the pods are believed to be poisonous. I do not presume to 

 say that they are not, but if so, the poison is of a kind which is not revealed 

 by chemical science. They are undoubtedly exceedingly indigestible, more 

 than nuts usually are, and the mischief they do may perhaps be attributed 

 to this cause. The woody fibre they contain forms a ball in the stomachs of 

 animals which feed on them. 



The weak-stemmed shrub (Trema aspera), which goes under the name of 

 " Elm," "Rough Fig," and (only in Queensland apparently), "Peach-leaved 

 Poisonbush," has often been recorded as poisonous, but neither chemical nor 

 physiological experiments can detect a poison. But it is a very fair fibre 

 plant, and would prove almost as indigestible to cattle as if they ate string. 



3. Hair-halls. 



There are many plants in which the presence of an injurious active prin- 

 ciple is certainly absent, but portions of the plant contain hairs which have 

 the property of felting, or of breaking up, and, while being unacted upon by 

 the stomach, agglutinate together and form substances called bezoars, or 

 from their origin, phytobezoars or hair-balls. 



The best known instance of this kind is afforded by the woolly inflorescence 

 of the Crimson Clover (Trifolium incarnatum), which has done much harm 

 to stock. See the paper on " Crimson Clover Hair-balls," by F. V. Coville 

 (Circular, U.S. Dept. of Agric. Botany, viii, 4). 



The spinules of the Prickly Pear (Opuntia) not only inflame the mouths 

 of cattle, sheep, and horses, but, when swallowed* form hair-balls. The 

 woolly seeds of the Cape Weed (Cryptostemma calendulaceum) are licked up 

 in great abundance by stock in summer and they readily produce hair-balls. 

 So do the stiff awns of oats, both the crop oat and the wild oat (Avena 

 fatua), and indeed other species. / 



Certain Brome grasses (Bromus) work similar mischief. 



4. Plants which irritate the mucous membranes. 



I have briefly referred to the Prickly Pear (Opuntia) with its barbed 

 spinules like a black-fellow's spear, designed to penetrate and not to 

 return. They cause intense irritation to the lips, tongue, stomach, and anus 

 of animals. When ripe, a puff of wind will blow them on to an animal; 

 it is not necessary to eat the plant on which they are found. 



Certain grasses have awns which are barbed, e*g., one of the barley 

 grasses (Hordeum murinum), figured and described in the Agricultural 

 Gazette for October, 1904, with an illustration of its work on the jaw of a 

 sheep. 



Then we have Chwtochloa (Setaria) Foxtail Grass, Avena sterilis (wild 

 oats), Bromus of many species (Brome grasses). All these are furnished 

 with barbed hairs or awns. 



Many such irritating grasses could be enumerated, but the present object 

 is to draw attention to them in a general way. 



