724 Hens low .— The Origin of Monocotyledons from Dicotyledons , 
6. Leaves of Large Size characteristic of many 
Aquatic Plants. 
With regard to the foliage, the enormous size to which the leaves can 
attain is a characteristic feature of certain hygrophytes and hydrophytes. 
Of the former are the Ferns just referred to, Gunner a, Rheum (from Rha, 
the old name of the Volga), Petasites (as contrasted with Tussilago ), &c. 
Of the latter may be mentioned the Victoria regia. Of Monocotyledons, 
Aroids, Bananas, and Palms illustrate the same fact, whether they be 
hygrophytes or not at the present time. On the other hand, the largest trees 
among Dicotyledons or Gymnosperms, such as Eucalyptus and Sequoia , 
have no such leaves. 
7. Water-storage Organs. 
If plants had been more or less aquatic, and subsequently became 
xerophytes, it is presumable that they would only be able to sustain life 
during great and prolonged droughts, by adopting methods of storing 
water. Such is not infrequent in both classes. Species of Erodium and 
many others utilize various internal structures for storing water in the 
deserts near Cairo. Oxalis cernua does the same in South Africa and 
Malta, &c. Poa hulbosa has swollen nodes in dry ground, but not in moist 
soil. 
Hence, tuberous roots, swollen internodes, bulbs, and corms are often 
acquired in adaptation to arid conditions on land. The prevalence of them 
among Monocotyledons, as seen in the orders Orchideae, Iridaceae, Amaryl- 
lidaceae, and Liliaceae, would seem to indicate an ancestral aquatic life. 
I would, therefore, regard the object of providing plants with corms, bulbs, 
and rhizomes to be threefold, viz. to enable them to be perennials, to 
be reservoirs of food, and if they be hydrophytes or hygrophytes which 
became xerophytes, then their third use is for water storage. 
8. The Requirement of much Water by many Terrestrial 
Monocotyledons. 
In support of this contention, not only are there still living aquatic 
members of the above-mentioned families, but under cultivation they all 
require a fair amount of water during growth, while some, such as Lilies, 
Aspidistra , &c., revel in it. 
£ Watsonia , for example, succeeds best when the saucer is kept full of 
water.’ This genus in cultivation 6 requires to be dried off gradually and 
then to be submitted to a baking in the sun ’, evidently in adaptation to the 
South African droughts. 
‘ Liliaceae, on the other hand, requires an abundance of water, and the 
genera never like being very dry ; so their bulbs should not be taken up. 
