84. CLASS-BOOK OF BOTANY, 
each cell. During ripening the outer involucre becomes hard 
and woody, and the ovaries mature into 3-angled winged 
nuts, in which only 1 seed is found, 
the other (if originally present) 
having its development arrested, 
The seed is exalbuminous, and 
has thick fleshy folded cotyledons 
enclosed in a thin testa; but thig 
feature is not readily visible until 
the seed is very ripe. 
Fig. 163. Tnvolucre of 
Fagus after the nuts 
have fallen (mag.). 
Fig. 164. 3-cornered Fig. 165. Nut of Fig. 166. Nut of Fagus, 
nut of Fagus Fagus, long. sec- trans, section (mag.). » 
(mag). . tion (mag.). 
The Oak and Hazel may be compared with the preceding. The de- 
velopment of the acorn furnishes a good example of the process of arrest, 
as out of the 6 ovules originally present in each ovary only one comes to 
maturity. | 
23. EuPHORBIA GLAUCA. 
This Spurge is common along the sea-coasts of these 
Islands, and perhaps is most familiarly known from the 
burning milky juice (latex) with which it abounds. Where 
this particular species cannot be readily obtained, one of the 
common introduced species, H. heltoscopia, H. peplus (a very 
abundant weed in many gardens), or the large H. lathyris, may 
be studied. The general structure of all these will be found 
to be the same. 
Fig. 168. Staminate flower 
Fig. 167. Inflorescence of of Euphorbia glauca 
EHuphorbia glauca (mag.). ee on to its pedicel 
mag.). 
_ The flowers are moncecious, one ? and several ¢ flowers 
being collected into an inflorescence, which is popularly 
termed the flower. This inflorescence is surrounded by » 
