130 FAMILIAR TREES 



he so deeply lobed as to appear like several. Their 

 lowers are invariably " unisexual " — " dicecious," for 

 ■example, or with stamens and seed-bearing flowers 

 on distinct trees, in the Yew, " moncecious," or 

 with stamens and carpels in distinct flowers but on 

 the same tree, in most others ; and, with hardly 

 an exception, the flowers are without any perianth. 

 Pollination is eSected by the wind, and there is 

 accordingly an abundant production of pollen. 



Each male flower consists of an elongated axis, 

 bearing scale-like staminal leaves, arranged either 

 spirally or in whorls : each of these scales may bear 

 two or more pollen-sacs ; and the round pollen-grains 

 have sometimes two bladder-like expansions filled 

 with air to aid in their dispersal. Unlike those of 

 Angiosperms, these pollen-grains undergo division 

 into two or more distinct cells ; and in one of these, 

 in a few cases, some Japanese botanists have recently 

 •detected spirally-coiled " antherozoids " or motile 

 sperm-cells resembling those of ferns and club- 

 mosses. This is the most striking confirmation of 

 the view that the group finds its nearest affinities 

 with the ferns and their allies. The female flower 

 has generally carpellary leaves; these are absent in 

 the Yew, and, when present are never close together 

 to form an ovary and stigma as in Angiosperms. 



The group comprises less than five hundred living 

 species, forming some forty-six genera, and these fall 

 into four larger groups or Orders. The Cycads of the 

 southern hemisphere, thick, cylindrical - stemmed 

 plants with a palm-like crown of leathery pinnate 

 Jeaves, are the lingering remnants of what was one 



