722 Hens low .— The Origin of Monocotyledons from Dicotyledons , 
torella , Drosera , Pinguicula , Menyanthes , Samolus , Primula , and most 
bulbous plants, &c. 
It must not be forgotten that starvation and strong light can produce 
the same arrest of the internodes, as seen in plants growing on walls, &c., 
as Dr aba, Sedum , Arabis Thatiana , and many others. So that this 
peculiarity of Monocotyledons is not caused by the arrested habit, but 
this itself may be the result of varying degrees of water, or else in conse¬ 
quence of other inducements. 
Degeneracy is very obvious where the aquatic form is contrasted with 
the land form of amphibious plants, such as Bidens cernua, Ranunculus 
Lingua , Polygonum amphibium , &c. As these plants grow equally well in 
either environment, they retain the capacity for adapting themselves to 
both conditions ; hence neither form is hereditary, so as to develop the 
characters of any one form when grown in a different environment. 
It is only, as a rule, after a prolonged residence of many generations 
(in water or in great drought, for example) that the acquired characters of 
adaptation are developed when the seeds are grown in totally different 
circumstances. Thus Ranunculus heterophyllus , the Water Crowfoot, retains 
the dissected and floating types of foliage on land ; and the fleshy Cactaceous 
plants ‘come true ’ to seed in England. 
Miss Sargant observes that ‘ Monocotyledons may be shown to be 
on the whole a decadent race, of which some branches have been driven to 
an aquatic habit to escape the severer competition on land ’. l Unfortunately, 
they do not escape it. Rivers, ponds, &c., soon get choked with a mixture 
of aquatic plants ; e. g. Water Crowfoots or Elodea. If by ‘ decadent * she 
means prior to their entry into water, the question arises—What caused 
the decadence on land? The author does not appear to see that it is zvater 
itself which has caused the degeneracy in all aquatic plants. 
‘ We may look on living Monocotyledons as a race which has been on 
the whole unsuccessful in the struggle for existence; and in consequence 
maintains itself chiefly in situations where the local conditions are excep¬ 
tionally favourable to its peculiar characters.’ 2 But grasses with 3,200 
species in all kinds of soils and climates are ubiquitous; Palms have 1,100 ; 
Orchids, 4,000 to 5,000 species, &c. Such do not seem to warrant Miss 
Sargant’s hypothesis. 
Degeneracy is well seen in the structure of the stems. The cylinders 
of wood of a Dicotyledon form a combination of girders, and whether 
hollow or not, afford ample strength to support the weight of the tree 
or herb ; but the dislocation of the strands in Monocotyledons brings about 
a mechanical weakness. Hence, palm stems made into walking-sticks are 
sometimes very brittle. The petiole of rhubarb leaves, naturally a hygro- 
1 Reconstruction, &c., p. 175. 
2 Reconstruction, &c., p. 176. 
