720 Hens low .— The Origin of Monocotyledons from Dicotyledons , 
Now if the order Cycadaceae, represented by the Bennettiteae, per¬ 
haps a very characteristic group of the Secondary Epoch, gives us any clue as 
to climate, then it might be inferred from the present distribution of the 
Cycadaceae that Monocotyledons arose in the warmer regions of the 
world. 
4. Degeneracy of Monocotyledons. 
Professor Sacco draws the conclusion from Palms being almost entirely 
restricted to the tropics, that they cannot adapt themselves to cooler 
temperate climates, either morphologically or physiologically. 1 
This would seem to apply, however, to the great majority of Mono¬ 
cotyledons in different degrees, and the explanation of the fact, I would 
suggest, is, that having become degenerate in structure by having lived 
originally in water, they cannot now, as land plants, recover to the full the 
power necessary to construct such tissues as are found in Dicotyledons 
capable of resisting the injurious effects of a cold climate. Moreover, having 
lost the power of making massive timber of concentric cylinders of wood— 
really girders in combination—they cannot support large trunks. 
The degraded condition of all Monocotyledons is also insisted upon 
by Prof. Hugo de Vries. He says: 2 ‘Monocotyledons are obviously 
a reduced branch of the primitive Dicotyledons. In Orchids and Aroids, 
in Grasses and Sedges, reduction plays a most important part, leaving its 
traces on the flowers as well as on the embryo of the seed. 
‘ The whole evolution of Monocotyledons from the lowest orders [?] of 
Dicotyledons implies the seeming loss of cambial growth and many other 
qualities.’ 
* Retrogression is everywhere so active, that it can almost be said to 
be the prevailing movement. Reduction in the Vegetative and Genera¬ 
tive organs, in the Anatomical structure and growth of the stems, and 
in sundry other ways, is the method by which the Monocotyledons, as 
a group, have originated from their supposed ancestors among the lower [?] 
dicotyledonous families. Retrogression is the leading idea in the larger 
families of the group, as for instance in the Aroids [especially their allies 
Lemnaceae] and Grasses. Retrograde evolution is also typical in the 
highest and most highly differentiated family, the Orchids, which have 
but one or two stamens.’ Prof, de Vries might have added the rudi¬ 
mentary condition of their ovules and seeds, and consequently the difficulty 
in securing the germination of Orchids. 
Prof, de Vries, like other writers, fails to see that water has been 
the cause of degeneration in Monocotyledons ; though all the now ter- 
1 L’Evolution biologique et humaine, p. 201. 
2 Species and Varieties, their Origin by Mutation, p. 15. 
