FLOWERS OP CONIFEROUS PLANTS. 23 



within a few weeks after it is produced, especially if the plant is 

 exposed to the direct action of the sun's rays. Partial variegation in 

 vigorous growing kinds often disappears entirely in the course of a few 

 years; it is also greatly influenced by the soil in which the plants 

 are growing, being heightened in some situations or soon becoming 

 obliterated in others. 



Glaucescence is quite distinct from variegation ; it makes its appear- 

 ance indifferently in young and old plants. It is always present in 

 the foliage of many species, in some of which it becomes greatly 

 heightened by age ; it also frequently appears with great intensity in 

 the young plants of species that are normally quite green or show it 

 but very faintly. The effect of glaucescence, as regards the aspect of 

 the trees, is to give them a greyish silvery hue, particularly pleasing 

 and beautiful in many plants belonging to the Cypress tribe and to 

 the Firs ; while it imparts a venerable hoary appearance to aged Pines, 

 and especially to the Cedar of Lebanon. It is believed to be due in 

 one form to the stomata of the leaves, and it is. not improbably an 

 optical effect arising from their close proximity and formal arrangement, 

 especially in the case of the white lines seen on the under surfaces of 

 the leaves of the Silver and other Firs, and in the leaves of Pines, 

 Junipers, &c. In another form it is caused by a resinous secretion 

 which" is easily rubbed off by the finger, leaving the leaf quite green. 



Flowers. — Trie Flowers are always without perianth, and are either 

 monoecious, as in the Fir and Pine tribe, or dioecious, as in the Tew 

 and Juniper.* Taking the flowers of the common Spruce, 

 the Larch, or the Scotch Pine (they are identical in 

 their general structure) as the type, we find the arrange- 

 ment of their parts to be thus : — The male flowers are 

 short catkins, consisting of a central axis to which are 

 attached minute imbricated scales, each scale bearing 

 at its extremity on the under side a pair of anther 

 or^ther^earing lobes, which burst longitudinally ; the female catkins 

 Kr^NahufS! also consist of a central axis, with closely imbricating 

 spirally arranged scales, each having at the base on its 

 upper surface a pair of inverted ovules. The pollen grains fall 

 direct upon the ovules, so that fertilization takes place without the 

 intervention of style or stigma. In the Cypress and Yew tribes 

 this type is slightly departed from, but they agree in having naked 

 ovules • in the former the scales of the male catkins bear generally 



* With a slight qualification— The Junipers and Taxads are not absolutely ' dicecious, 

 but relatively so, monoecious plants having been observed. 



