324 BOTAXICAL GAZETTE ' [october 



The investigations of Bowman were in the Dry Tortugas, and include 

 many details regarding the morphology and structure of the various organs 

 of the tree, including development and growth rate of the viviparous embryos. 

 Measurements of the latter show a 4.7 cm. elongation of the emerging hypo- 

 cotyls in 34 days. The results of transpiration studies show a lower rate of 

 water loss with higher concentrations of sea water. The red mangrove is 

 facultative in its growth in fresh and salt water, but requires the latter for 

 optimum development. At least 2000 sq. miles of the tidal flats of the Philip- 

 pine Islands are occupied by mangrove forests. The floristic, ecological, and 

 economic characteristics of these forests of the sea have been described by 

 Brown and Fischer. 1 * Keys are provided for the recognition of the 30 prin- 

 cipal species belonging to 16 different families. In addition to the well known 

 aerial roots and viviparous habit of the mangroves, some of the notable 

 features of these woodlands are the scanty undergrowth, the fairly numerous 

 epiphytes, the myrmecophilous plants, and the frequent fringing of Nipa 

 palms. 



While the original stands of this forest contain trees of fair size yielding 

 hard cabinet woods of excellent quality, the greater portion of the area is 

 important only for the production of a good quality of firewood and for tan 

 bark. The Nipa palm is important for alcohol production, and seems to 

 present a possibility of utilization for sugar. Some cultivation of both the 

 mangroves and the Nipa palms has proved successful; the former has also 

 been used with good results in planting dykes and embankments to prevent 

 the erosive action of the sea. — Geo. D. Fuller. 



Age and area hypothesis. — The development of this hypothesis by Willis 

 has been noted in this journal, 15 and now an analysis of the flora of New Zealand 

 seems to strengthen his contentions. 16 The evidence in favor of the majority 

 of endemics being of recent origin rather than relics is rather convincing. 



Recently a floristic study of the plants of Stewart Island 17 yielded results 

 supporting the hypothesis of the families and genera being represented in 

 proportion to the number of genera and species respectively contained in 

 them in New Zealand. The oldest forms are best represented in the flora, 

 and the endemics are in the largest (in general, oldest) families and genera 

 of New Zealand. 



14 Brown, Wm. H., and Fischer, A. F., Philippine mangrove swamps. P.I. 

 Dept. Agric. and Nat. Res., Bur. For. Bull. 17:132. pis. 47. 1918. 



15 Box. Gaz. 61:82. 1916; 62:160. 1916; 63:419. 1917; 64:263. 1917; 6 5 : 

 116-117, 486. 1918. 



16 Willis, J. C, The sources and distribution of the New Zealand flora, with a 

 reply to criticism. Ann. Botany 32:339-367. 1918. 



17 % The flora of Stewart Island (New Zealand): a study in taxonomic 



distribution. Ann. Botany 33:23-46. 1919. 



