From the prevalence of cycads we may conclude that the climate of the Wealden and Lower Greensand was sub-tropical.
But these specimens found at Luccombe show that cycads at that time were developing into flowering plants.
Cycads and other vegetable remains are found in this neighbourhood.
But these flowering cycads must have formed a marked addition to the landscape,--if indeed they did not already exist in the Wealden times.
Among the cycads the predominance of Zamites and Nilsonia, and among the ferns the numerous genera with leaves having reticulated veins (as in fig.
Cycads are extremely rare, and of Monocotyledons there are but few.
Among the cycads the predominance of Zamites, and among the ferns the numerous genera with leaves having reticulated veins (as in Figure 349), are mentioned as botanical characteristics of this era.
The angiosperms seem, therefore, to have been at the least comparatively rare in these older secondary periods, when more space was occupied by the Cycads and Conifers.
Alongside these vegetable families, which passed upwards from the preceding age, an entire family--the Cycads (Fig.
The Cycads were still represented by the Zamias, and by many species of Pterophyllum.
Cycads sharing at once in the organisation of the Conifers and the elegance of the Palms, now decorate the earth, which reveals in these new forms its vast fecundity.
Closely bound up with this topic were his studies on the Cycads and Conifers.
In the Triassic period, however, the remains ofCycads belonging to such genera as Pterophyllum (fig.
So with some Cycads and other plants of distinct habit--the very things best fitted to add to the attractions of the flower-garden.
Webber, and more recent work enables us to assume that all cycads produce ciliated male gametes.
The roots of some cycads resemble the stems in producing several cambium-rings; they possess 2 to 8 protoxylem-groups, and are characterized by a broad pericyclic zone.
Similarly in the sporophylls of some cycads the bundles are endarch near the base and mesarch near the distal end of the stamen or carpel.
The anatomical structure of the vegetative organs of recent cycads is of special interest as affording important evidence of relationship with extinct types, and with other groups of recent plants.
Surrounding the pitted wall of the ovum there is a definite layer of large cells, no doubt representing a tapetum, which, as in cycads and conifers, plays an important part in nourishing the growing egg-cell.
The cycads constitute a homogeneous group of a few living members confined to tropical and sub-tropical regions.
The leaf-traces of cycads are remarkable both on account of their course and their anatomy.
The spermatozoids constitute the most striking link with both cycads and ferns.
Orchid& display sprays of yellowish-green flowers, which contribute a decided savour to the medley of scents, and palm-like Cycads meander from the low bank out Into the forest.
The large pinnate or rarely bipinnate leaves give the Cycads a superficial resemblance in habit to Palms.
Similarly, Cycads may have got what practically amounted to flowers at the time when they were the dominant group, and it is very conceivable that they did not lead on to the main line of flowering plants.
Whether they led directly on to theCycads is as yet uncertain, the probability being rather that they and the Cycads sprang from a common stock which had in some measure the tendencies of both groups.
The morphological leap from the leaves and stems of cycads to those of the flowering plants seems a much more serious matter to presuppose than is at present recognized.
The Cycads The group of the Cycadales, which has a systematic value equivalent to the Ginkgoales, contains a much larger variety of genera and species than does the latter.
Thus can the flowering plants be linked on to the series that runs through the Cycadsdirectly to the primitive ferns!
Plant of Cycas, showing the main stem with the crown of leaves and the irregular branches which come on an old plant] In their fructifications the Cycads stand even further apart from the rest of the Gymnosperms.
In Mesozoic times the most striking group is that of the Cycads and Bennettitales, the latter branch suggesting a direct connection between the fern-cycad series and the flowering plants.
These fossils appear to be ferns, though their modern allies have not been indicated with certainty; associated with them are rare cycads and conifers.
Cycads predominate, accompanied by conifers, and a fair number of ferns and Equisetaceae.
It has been noted in the last chapter that the gymnospermous flora of the Jurassic period, in which cycads form a considerable percentage of the whole flora, was prevalent in Lower Cretaceous times.
Palms are so like cycads that we may regard them as the descendants of some cycad type.
Many supposed fossil Cycads are looked upon by Carruthers as Coniferæ.
In the Wealden at Brook Point, Isle of Wight, Cycads have been detected allied to Encephalartos.
The greater part of the cycads of the Mesozoic age would seem to have had short stems and to have constituted the undergrowth of woods in which conifers attained to greater height.
Some plants referred to the cycads have proved veritable botanical puzzles.
In the Jurassic rocks of Europe and India some flowers not very unlike these have been found, which have been named Williamsonia, and referred to cycads by Carruthers.
The ferns and cycads of the so-called Lower Cretaceous of Greenland are nothing but a continuation of the previous Jurassic flora.
The berries and nuts of the numerous yews and cycads were capable of affording much food.
The cycads have usually simple or unbranching stems, pinnate leaves borne in a crown at top, and fruits which, though somewhat various in structure and arrangement, are all of the simpler form of gymnospermous type.
The reign of cycads and pines holds throughout the Lower Cretaceous, but at the close of that age there is a sudden incoming of the higher plants, and a proportionate decrease, more especially of the cycads.
Whether they were winged fruits or seeds, or fruits with a pulpy envelope like those of cycads and some conifers, may be considered less certain.
But among the Conifers and Cycads our modern flowering plants were beginning to show face tentatively, just like birds and mammals among the great reptiles.
But let us try the tree-ferns and cycads of the coal beds of the "older" rocks.
The Cycads are absolutely restricted to the tropics, a few forms reaching into semi-tropical conditions, as in southern Florida.
If a comparison be made between the eastern and western tropics, it will be discovered that the Cycads are almost equally divided between the two regions.
For an unknown time, but certainly a very long one, these eastern and western Cycads have been separated from one another.
The cycads reached their culmination in the Jurassic period, but they still exist in modified form in some parts of the world.
In fact, thecycads are distantly related to the palms, which belong to a higher group of plants.
These were the cycads and conifers, which were the most conspicuous trees during the first two periods of the Mesozoic era.
There were now palmlike cycads and many tropical conifers, though as yet there were no flowering plants and no grasses.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "cycads" in a variety of sentences. We hope that you will now be able to make sentences using this word.
