PHANEROGAMIA 



489 



Fio. 455. Longitudinal .section of a young 

 macroeporangium of (linkgo biloba, m, 

 micropyle ; ', integument ; p, pollen- 

 chamber ; e, embryo-sac ; w, outgrowth 

 of siwrophyll. The possession of a well- 

 developed pollen-chaml^r jxiints to the 

 relationship with the Cycadaceac. (x 

 35. After COULTER and CHAMBERLAIN.) 



becomes filled with a continuous tissue and forms the embryo at the end farthest 

 from the micropyle. This grows out and 

 penetrates the endosperm, but there is no 

 clear distinction into suspensor and embryo. 



Order 3. Coniferae ( 7 ) 



The Coniferae include conspicuous 

 trees or shrubs with woody stems. 

 The possession of small, undivided, 

 firm leaves, flat or needle-shaped, and 

 usually lasting for several seasons, 

 is a common character of the plants 

 of the order ; they are thus for the 

 most part evergreen. All Conifers 

 are profusely branched, arid a distinc- 

 tion into long and short shoots is 

 usually evident. In many cases the 

 direction and rapidity of growth of 

 the main axis differs from that of the 

 lateral branches. This is especially seen in young individuals ; old 

 trees are often more irregular in outline. 



The absence of vessels from the xylem of young plants and from 

 the secondary wood is an anatomical characteristic (cf. p. 134). Their 

 place is taken by large tracheides with peculiar bordered pits on the 

 radial walls ; these form a very uniform wood. The majority of the 

 Coniferae have resin abundantly present in all the parts of the plant. 



The Coniferae in contrast to the Cycadinae are mostly inhabitants 

 of temperate regions, and are among the trees which approach nearest 

 to the polar regions. Within the tropics they are mostly confined to 

 mountains. 



The Coniferae are divided into two families on account of differ- 

 ences in the floral structure. 



The Taxaceae have female flowers with one or few macrosporangia ; 

 the latter are usually provided with an arillus. The flowers are 

 usually not definite cones. Mostly dioecious. 



The Pinaceae on the other hand have a number of ovules in each 

 female flower, the latter being a cone with numerous sporophylls 

 borne on an axis. Arillus not present, usually monoecious. 



Family Taxaceae. The plants belonging to this family are grouped in a 

 number of small genera distributed in the southern hemisphere. The most 

 important genus is Podocarpus, the numerous species of which are widely distributed 

 in temperate East Asia and in Australia and New Zealand, and also occur as stately 

 trees on the mountains of the Asiatic tropics. The female flowers are small 

 shoots, the sporophylls of which are swollen and succulent : one or two of them 

 bear at the summit a single anatropous ovule surrounded by a fleshy arillus. 

 The male flowers, which are borne on the same or on distinct individuals, are small 



