THE WEEDS OF CULTIVATION 



is found in cornfields, creeping 

 along the ground. When the corn 

 has been cut, the plant is in fruit, 

 and its dehiscence should be noted. 

 It splits transversely, allowing the 

 top to be lifted off like a lid. The 

 majority of capsules split longi- 

 tudinally, therefore this transverse 

 dehiscence is interesting. The 

 bright scarlet flowers expand only 

 in fine weather, hence the name 

 Poor Man's Weather-glass has been 

 given to the plant. The Petty 

 Spurge (Euphorbia Peplus) is an 

 annual. The peculiarity of structure 

 in the Spurges is that each appar- 

 ent stamen is a flower, for each 

 has a minute scale at its base. The 

 cup-shaped structure, which at first 

 sight may easily be taken for a . 



FIG. 38. Petty Spurge (Euphorbia 



corolla, is an involucre furnished p e pius\ s , Staminate flowers , p, P is- 



with four Or five teeth and with tillate flower ; g, glands ; *, involucre. 



brownish yellow glands. The pistillate flower 

 in the centre has a three-celled ovary ; the 

 styles are three, and the whole flower hangs 

 down. In the Spurges then, what appears to 

 be a single flower is an inflorescence. All the 

 Spurges have a milky juice which is often 

 poisonous. Many well-known foods are pre- 

 pared from plants belonging to this order. 

 Tapioca comes from the West Indian Cassava. 

 There are two species of Cassava common in 

 the West Indies. The root of the Sweet 

 Cassava is eaten as a vegetable ; the Bitter 

 Cassava is highly poisonous, but a flour is 

 prepared from it by extracting all the 

 poisonous juice, and out of this the thin 



Fir, 39. Field Pennycress J , ,., ... 



i arveme) Cassava cakes, which visitors to the West 



