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CYCADS. 



By Mr. W. Caeeuthees, F.R.S, 



[Bead October 18, 1892.] 



In appearance cycadaceous plants resemble Palms, and are not 

 unlike Tree-Ferns, but they are really related to the Pine family. 



The earlier botanists could not make out what they were. 

 Now we know that, associated with two other groups, they form 

 a distinct division of flowering plants. 



In the fertilisation of the plants we are most familiar with, 

 the pollen-grain falls upon or is conveyed to the stigma, and 

 then sends down a slender tube through the substance of the 

 style until it reaches the ovule and fertilises it. Plants thus 

 fertilised belong to the higher class of phanerogamous or 

 flowering plants. In the Cycadea?, however, the pollen-grain 

 does not rest upon a stigma, nor pass through the substance of 

 the style before reaching the ovule, but comes into direct contact 

 with it. The ovule is not enclosed in a carpel, but is more or 

 less freely open to the air ; they are consequently called naked- 

 seeded or gymnospermous plants. The group is a small one, con- 

 taining not more than 400 species, which are distributed into 

 three orders, viz. : — 



(1) The Gnetacea3, represented by Gnetum Ejphredra and the 

 marvellous Welwitschia — a huge vegetable baby which lives for 

 a century or more, and produces only one pair of leaves after the 

 cotyledonary ones. 



(2) The second order is the Conifer a?, to which belong the 

 Pines, Larches, Firs, Yews, &c. Coniferous plants are distributed 

 over large tracts of the northern hemisphere, and are compara- 

 tively rare in the southern. 



To-day I ask your attention to the third order, the Cycadea?. 

 But first let me say that gymnosperms are most important 

 plants in the history of the vegetation of our globe. They form 

 a part of the first dry-land flora with which we are acquainted, 

 petrified fragments of their wood being preserved in rocks of 

 Devonian or Old Bed Sandstone age. In the carboniferous rocks 

 many genera and species related to the Yews have been found. 

 Some of them attained a great size, At the Natural History 



