II ARISTOLOOHIACE^ — EUPHORBIACE.E 351 



insect visitors are principally small flies. A Soutlieru 

 European plant found in several English counties, but 

 regarded by Watson as a denizen. 



EUPHOEBIACE^ 



Euphorbia 



The plants are protected by a milky acrid juice. 

 The flowers secrete nectar, which lies quite exposed. 

 The apparent flowers are really flower-heads. The cup- 

 shaped involucre has 4 or 5 rounded or moon-shaped 

 glands, which secrete a thin covering of nectar. It 

 contains 10-15 stamens, each of which is jointed, 

 showing that it represents a stalk bearing a flower 

 which is reduced to a single stamen,^ and in the centre 

 is a single female flower consisting of a 3 -celled ovary 

 and 3 styles, each terminating in 2 stigmas. The 

 flower -head is protogynous. The flowers are occa- 

 sionally visited by bees and wasps, but fertilisation is 

 almost exclusively due to flies. According to Kerner 

 the anthers close in wet weather. The seeds difier con- 

 siderably. Some are smooth (E. hyberna, E. Paralias, 

 E. amygdaloides); some pitted \E. Peplus, E. pep- 

 loides, E. Helioscopia, E. segetalis); some wrinkled 

 [E. exigua, E. Lathyris); others dotted, or tubercular. 

 The capsule, as a rule, opens both loculicidally and 

 septicidally, so that each valve consists of one half of 

 a carpel. 



Merctjrialis (Dog's Mercury) 



Wind flowers ; generally dioecious. 



AVe have two species — one annual, the other peren- 

 nial. In both, male flowers sometimes, though rarely, 

 occur on the female plants. There are Only two carpels. 

 The outer skin of the fruit of M. annua,^ which is 



■' An interesting confirmation of this view is afforded by a foreign genus, 

 Anthostema, which has a distinct perianth. 



^ Lcclerc du Sablon, Ann. Sci. Kat. xviii. (1884). 



