2008 



A TEXTBOOK OF THEORETICAL BOTANY 



flowers and edible fruits, which is sometimes cultivated in southern 

 parts of Britain as a wall climber. 



ARALES 



The Arales are Monocotyledons in which the flowers are either herma- 

 phrodite or unisexual, consisting of dimerous or trimerous whorls or some- 

 times reduced to a single stamen and carpel. The ovary is superior. The 

 fruit is a berry with the testa of the seed fleshy and enclosing endosperm in 

 many cases. 



The plants are mostly herbs, often of large size, occasionally shrubs, of 

 very variable habit. The leaves are usually radical but if attached to the 

 stem they are arranged alternately. The small flowers are arranged in a 

 spadix or spike, usually subtended by a spathe. 



This order, which is due to Hutchinson, includes two families, Araceae, 

 sometimes termed the Aroideae by earlier writers, and the Lemnaceae, the 

 latter containing very greatly reduced floating aquatic plants collectively 

 termed the Duckweeds. Though the Araceae are represented in Britain only 

 by two genera, the family is of sufficient general interest to be considered 

 in detail. The Lemnaceae however are of minor importance except from a 

 morphological standpoint and in that connection they have already been 

 discussed in Volume L We need therefore only refer to them briefly here. 



I 



Fig. 1945. — Lemna tnsulca. A, Germinating seed with oper- 

 culum being pushed off by the cotyledon. B, Young seed- 

 ling. Primary root (with cap) and plumule arising from the 

 cotyledon. C, First and second fronds arising from the 

 plumule. {After Hegelmaier.) 



