486 



PART III. THE CLASSIFICATION OF PLANTS. 



preceding genera, the seeds are all borne on the placental region of the macro- 

 sporophyll and are inverted ; in the following genera the seeds are axillary and 

 erect. Cryptomeria has an erect fringed placental outgrowth. Taxodium, is 

 the deciduous Cypress of North America ; its leaf-bearing twigs are thrown off 

 each year (T. distichum), or persist for two years (T. mexicanum) : the placental 

 outgrowth overgrows the macrosporophyll as the cone ripens. Glyptostrobus 

 is the Chinese Water Pine ; it differs from Taxodium only in that the seed has 

 a wing. 



Fam. 4. Cupressinece : monoecious, sometimes dioecious: macrosporophylls 

 with a projecting placental outgrowth: seeds axillary, erect, often winged: 

 microspores without expansions of the exine : leaves always arranged in whorls. 

 In the sub-family Actinostrobince, including the genera Actinostrobus, Calli- 

 tris, and Fitzroya, the ripe cone is woody and the constituent macrosporophylls 

 are arranged in a valvate manner. 



In the sub-family Thujopsidince, including the genera Thujopsis and Thuja 

 (incl. Libocedrus and Biota) the ripe cone is woody and the constituent macro- 

 sporophylls are arranged in an imbricate 

 manner. The most familiar species are 

 Thuja occidentalis, the American Arbor 

 Vitae, and Thuja (Biota) orientalis, the 

 Chinese Arbor Vitse. 



In the sub-family Cupressince, includ- 

 ing the genera Cnpressus and Chamaecy- 

 paris, the ripe cone is woody and con- 

 sists of 2-6 pairs of peltate macrosporo- 

 phylls coherent by their margins in a 

 valvate manner. The genus Cupressus, 

 the Cypress, has several seeds on each 

 macrosporophyll : in Chamaacyparis each 

 macrosporophyll bears only two seeds. 



The sub-family Juniperince, including 

 the single genus Juniperus, is distin- 

 guished from the preceding sub-families 

 in that the flowers are, as a rule, dioe- 

 cious ; the ripe cone is somewhat fleshy, 

 resembling a berry or a drupe ; it usually 

 consists of one whorl of macrosporophylls 

 each bearing one or two wingless seeds. 

 The section Caryocedrus (Arceuthos), containing the single species Jumper us 

 drupacea, has a cone consisting of 3 or 4 whorls of macrosporophylls ; whereas 

 in the section Oxycedrus (including Juniperus communis, the Juniper ; J. Oxy- 

 cedrus, J. macrocarpa, and other species), the cone consists of 1-2 whorls ; and 

 in the section Sabina (including J. Sabina, J. virginiana, etc.), it consists of 2-3 

 whorls ; the innermost or uppermost whorl alone is fertile as a rule, in Caryo- 

 cedrus and in Oxycedrus, but is sterile in Sabina : in Caryocedrus the (2-3) seeds 

 are coherent, in the other two sections they are free : in Sabina the flowers 

 are generally monoecious ; in Sabina also the leaves (including sporophylls) are 

 usually in whorls of 2, whilst in the other two sections they are in whorls of 3. 



FIG. 306. A Branch of Thuja occi- 

 dentalism (x6) showing heterophylly ; fe 

 flank-leaves ; / surface-leaves ; 7i resin- 

 receptacle (see p. 464). B Fruit of Biota 

 orientalis (nat. size) : / macrosporophylls 

 with ventral outgrowths d; d (in the 

 middle line) sterile sporophylls. 



