ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 647 



one another in the centre. The secondary increase in thickness of 

 the root is anomalous in several respects. The thin-walled parenchyma, 

 whether it increases radially or tangentially, i. e. whether it forms 

 medullary rays or wood-parenchyma, remains capable of growth in all 

 directions, and therefore of forming new cambium. Details are 

 also given of the structure of the root in other species of Polygala. 



Partition of the Axis.* — M. D. Clos applies this term to any mode 

 of division of the stem or root, restricting the term " dichotomy " to 

 its older signification, the elongation of two buds produced in the axil 

 of two upper leaves. 



Partition of the root, or polyrhizy, may be of four different 

 kinds: — (1) The fasciculate roots of monocotyledons and of some 

 dicotyledons, where the main axis is more or less destroyed, or very 

 feebly developed (Inula Conyza). (2) Partition of the main axis into 

 two, three, or four equal or unequal branches (Scorzonera, Daucus, 

 Bumex, Cucurbita Pepo and maxima). (3) Bipartition of adven- 

 titious and especially of fleshy roots (Dioscorea Batatas). (4) 

 Arrangement of the secondary roots in small bundles along the main 

 axis (Beseda, Fumaria.) This may occur also on cladodes of Opuntia 

 kept some time in water. 



Partition of the axis generally may be classed under the three 

 heads of Bipartition, Tripartition, and Multipartition or Polyclady. 

 Bipartition may be equal or unequal, and either of these may be 

 normal or abnormal. 



A large number of special cases are described, taken from a great 

 variety of natural orders. 



Relation between the Bloom on Leaves and the Distribution 

 of the Stomata.f — Mr. F. Darwin finds a connection between the 

 relative number of stomata on the upper and under surface of leaves 

 and the presence of " bloom " or the coating of wax which protects the 

 stomata from the rain which would otherwise close them and render 

 them useless. In those leaves which have no bloom on either surface 

 there is a strong tendency towards the accumulation of stomata on the 

 lower surface ; in all those in which the bloom occurs on the upper 

 surface only, there are also stomata on that surface ; while of those 

 which have bloom on the under surface only, 83 per cent, are entirely 

 destitute of stomata on the upper surface. 



Double Flowers. $ — Rev. W. Woolls remarks that few double 

 flowers have as yet been found amongst the Australian plants in the 

 wild state. He mentions the Epacrids as having an especial tendency 

 to produce double flowers, e. g. Epacris purpurascens, E. microphylla, 

 E. impressa, Sprengelia incarnata, Astroloma humifusum. Amongst 

 other orders he has found the following plants : Banunculus lappaceus, 

 Eriostemon obovalis, Boronia pinnata, Wahlenbergia gracilis ; the last 

 is remarkable as it so soon loses its stamens after flowering. Although 



* Mem. Acad. Sci. Toulouse, vii. (1885) pp. 222-56 (2 pis.), 

 f Jouru. Linn. Soc. Lond. (Bot.), xxii. (1886) pp. 99-116. 

 X Proc. Linn. Soc. N. S. Wales, x. (1885) pp. 455-8. 



