209 



SHORTER NOTES 



Relation of Sunshine to the Habitat of Rottboellia 

 exaltata (Poaceae) — In the Philippine Islands Rottboellia exaltata 

 is a good example of a plant, which although relatively intolerant, 

 does not long survive full sunshine. Because it grows throughout 

 the year, the consequences of this relation become conspicuous 

 at certain seasons. At the borders of woodlands and in the edges 

 of thickets Rottboellia grows luxuriantly all the year round. 

 Within woods and thickets however it is not present. Rott- 

 boellia is a weed common to corn and rice fields. When the land 

 lies after the harvest, Rottboellia frequently becomes entirely 

 dominant. This takes place in the latter part of the rainy 

 season when there is a high percentage of cloudiness. The 

 luxuriant growth reaches an average height of six feet in the open 

 but at the edge of woods it is somewhat higher and more spindling. 



As the amount of sunlight increases with the approaching dry 

 season, a great change takes place. Gradually the grass growing 

 in the full sun dries up and falls over, resulting in the reduction 

 of the height of the vegetation from that of Rottboellia (6 feet) 

 to that of the plants heretofore growing beneath it, for example, 

 Mimosa pudica (i foot). Meanwhile plants of Rottboellia in the 

 partial shade of the edge of thickets continue to develop and 

 flower throughout the dry season. If, however, the partial 

 shade be removed, the Rottboellia plants dry up and fall over. 



Thus we have in Rottboellia exaltata an example of a plant 

 whose habitat in the dry season is restricted to partial shade on 

 account of its inability to withstand full sunshine. 



F. C. Gates. 



Douglas Lake, Michigan, 

 August, 1915. 



REVIEWS 



Dixon's Transpiration and the Ascent of Sap in Plants'" 



For over seventeen years botanists have been familiar with 

 Prof. Dixon's papers, embodying the results of his scholarly 

 investigations on the subject of transpiration and the ascent of 



* Dixon, Henry H. Transpiration and the ascent of sap in plants, pp. i-vi 

 and 1-216. figs. 1-30. Macmillan & Co. London, 1914. $1.40 net. 



