The President's Address. By Lord Avcbury. 139 



outer or lower whorls remain small and infertile ; the scales are 

 triangular, with an acute cuspidate point, and arranged in six rows. 

 The leaves of one or two of the inner whorls alone are fertile, each 

 bearing one or two ovules. These enlarge, gradually envelop the 

 seeds, become fleshy and more or less connate, forming what 

 appears to be a berry, at first green but ultimately blue-black and 

 glaucous. It takes two years to mature. Each fruit contains three 

 to six, or even more, seeds. The seeds are ovoid or trigonous, or 

 variously angled by mutual pressure, and contain much resin. The 

 testa is hard and bony. 



In J, nana the fruits are rather longer in proportion. 



Taxiis (the Yew). — In the Yew the flowers are mostly dioecious ; 

 the scales remain small and infertile, while a single ovule at the 

 apex of the twig develops, and is surrounded by a large, cup-like, 

 pulpy aril. This is a favourite food of thrushes, which either 

 swallow the fruit entire, or reject the stone when swallowing the 

 aril. In either case the hard woody coat of the seed preserves it 

 from digestion, and it passes through the alimentary canal without 

 injury to the embryo. 



CYCADAOEiE. — The Cycadacea?-, which used to be placed near the 





r 



Fig. 21.— Cycas. Section through Fig. 22.— Mature anthe- 



nearlv ripe spermatozoid. x 300. rozoid of Zamia. x 90. 



After" Ikeno. (From Journ. Coll. After Webber. (From 



Sci. Imp. Univ. Tokio, 1898-1900, Bot. Gaz., xxiv. 1897, 



pi. xiii. fig. 32.) p- 18, fig. 4.) 



Palms, or even the Tree-ferns, are evidently more nearly related 

 to the Conifers. 



The ovules are naked, sessile, and orthotropous. The seed is 

 drupe-like, with several openings corresponding to the embryonic 

 vesicles, from which proceed folded cords, terminating in embryos, 

 one of which only is developed. The testa is fleshy outside, 

 crustaceous within' ; the albumen is fleshy, with a central cavity in 

 which is the embryo. The cotyledons cohere so closely, that there 

 seems to be only one. 



A very remarkable point connected with the Cycadacea? is that, 

 as already mentioned, they possess mobile so-called spermatozoids. 

 The large pluricellular pollen-grains are sucked into the pollen 

 chamber, which is provided with a special strand of tracheides 



l-2 



