No. 2, March, 1921] MORPHOLOGY, ETC., VASC. PLANTS 159 



author's interpretation of the leaf structure on the basis of that theory is given. The species 

 studied belong for the most part to the Asphodeloideae and Allioideae. The evidence, which 

 is given in detail for each species studied, is considered to indicate that in different cases the 

 leaf is morphologically (1) leaf-base phyllode, (2) petiolar phyllode, (3) chiefly leaf-base with 

 small petiolar region, and (4) chiefly petiole with small leaf-base region. — W. P. Thom-pson. 



1052. Arber, Agnes. The vegetative morphology of Pistia and the Lemnaceae. Proc. 

 Roy. Soc. London B. 91 : 96-103. 8 fig. 1920. — Engler's early work on lemnaceous homology 

 of Pistia is confirmed and extended. Presence of row of inverted bundles in "limb" of Pistia 

 indicates that it is a petiolar phyllode, and this finding is applied to Spirodela, in which the 

 inverted bundles are missing. In the latter plant, buds are borne in lateral pockets formed by 

 ligules on either side of limb or frond. In Pistia the limb is fused along its median line 

 with the rudimentary plant axis, leaving no space for axial buds; consequently buds occur 

 at one side in recessed pockets com.parable with those in Spirodela. — Paid B. Sears. 



1053. Boodle, L. A. The mode of origin and the vascular supply of the adventitious 

 leaves of Cyclamen. Ann. Botany 34: 431-437 6 fig. 1920. — When seedling tubers of CycZa- 

 7nen are decapitated, adventitious leaves develop usually from near the margin of the cut and 

 occasionally from the cut surface itself. The development of these leaves and particularly of 

 their vascular supply is described. The internal tissues of the leaf are always derived from 

 the sub-epidermal tissues of the tuber; but the epidermis of the leaf may be either epidermal 

 or subepidermal in origin, depending on whether periderm had previously been developed. 

 The procambial strands develop rapidly from the leaf rudiment inwards, soon forming con- 

 nections with two or three bundles of the tuber. All the cells in a transverse section of a 

 strand are derived from a single cortical cell. No definite opinion is reached in regard to the 

 nature of the stimulus requisite for the initiation of the leaf trace, but reference is made to 

 Simon's conclusion that in somewhat analogous cases the stimulus depends on the distri- 

 bution of water in the tissues.— W^. P. Thompson. 



1054. Brewster, A. A. Aril of Cupania and Synoum. Australian Nat. 4: 170. 1920. 



1055. Brewster, A. A. Microzamia or burrawang. Australian Nat. 4:162-164, 167, 

 169. PI. 3. 1920. — A popular account of the morphology of the flower, seed, and seedling.— 

 T. C. Frije. 



1056. Brown, Elizabeth Dorothy Wuist. Apogamy in Osmunda cinnamonea and O. 

 Claytoniana. Bull. Torrey Bot. Club 47:339-345. 10 fig. 1920.— Only one case has pre- 

 viously been reported of apogamy in Osmunda. Descriptions are given in this paper of 

 one case in 0. cinnamonea, and of three in 0. Claytoniana, but none occurred in cultures of 

 0. regalis. — P. A. Munz. 



1057. Brown, Forest B. H. The silicious skeleton of tracheids and fibers. Bull. Torrey 

 Bot. Club 47: 407-424. 5 fig. 1920.— Secondary xylem, when it shrinks or swells, does not 

 change in length, yet details of anatomy have not shown why one dimension of the cells con- 

 cerned should vary independently of another. A study of the minute structure of the sec- 

 ondary thickening of the walls in fibers and tracheids of wood and in fibers of bast, shows 

 that there is a greater mineralization in parts of this wall than in the rest. These mineralized 

 tracts run longitudinally and form a skeletal structure going from one end of the cell to the 

 other. These rods imbibe little or no water and allow practically no change in length, but the 

 matrix between them, by swelling or shrinking, permits tangential or radial change in volume. 

 The structure of the fiber wall was found to be essentially the same in some 500 species 

 studied, the skeleton consisting of sparingly branched rods which become reticulate in the 

 vicinity of pits or have transverse connections. These skeleton rods seem to be silicious in 

 many cases, although there is variation in different families, genera, or even species as to com- 

 position. They can be demonstrated by partial combustion of a section on a slide, the por- 

 tions along the burned margin showing small noncombustible rods. — P. A. Munz. 



