38 ECOLOGY, PLANT GEOGRAPHY [Bot. Absts., Vol. IV, 



262. Sharples, A. The laticiferous system of Hevea brasiliensis and its protective func- 

 tion. Ann. Botany 32:247-257. 1918.— See Bot. Absts. 1, Entry 1409. 



263. Shreve, Forrest. The Jamaican filmy ferns. Amer. Fern. Jour. 3:65-71. Sept., 

 191S. — Though forty-nine species of filmy ferns have been reported for Jamaica, the author 

 was able to find but thirty-three; eighteen of Trichomanes and fifteen of Hymenophyllum. 

 These filmy ferns show a considerable diversity of habit, structure, and habitat which does 

 not seem to be true of those from Ceylon and Java. An abundant supply of surface moisture 

 is necessary because of the delicate structure of the fronds which are but one cell thick and 

 have no epidermis, stomata or intercellular spaces. They occur on the deeply shaded floor 

 of the lowland forests; at higher elevations, where the moisture is more abundant, they grow 

 as climbers or epiphytes above the forest floor. Brief descriptions are given of some of the 

 main types, and attention is directed to two special adaptive features; (1) in some of the 

 more segmented forms a hairy coat is developed which aids in the retention of moisture, thus 

 preventing extreme desiccation; (2) some of the epiphytic forms growing well above the forest 

 floor where the air is relatively dry have undergone a physiological adaptation by reason of 

 which the cells are enabled to lose a great amount of water for a short period without serious 

 results. — P. D. Strausbaugh. 



264. Small, James. The origin and development of the Compositae. Chapter IX. Fruit 

 dispersal. New Phytol. 17 : 200-230. 4 fig- Nov., 1918. Experiments with a special appa- 

 ratus on the fruits of Taraxacum and other composites definitely prove the efficiency of pap- 

 pus in wind dispersal over wide areas. Discrepancies with observers who have minimized 

 the efficiency of pappus are explained by assuming that the problem is one of hydrodynamics, 

 instead of hydrostatics, as it has been commonly regarded. A pappose fruit is more com- 

 parable to an aeroplane or kite than to a parachute or balloon. It is concluded that with a 

 relative humidity not exceeding 0.77, a horizontal wind with a velocity of 1.97 miles per 

 hour can transport a Taraxacum fruit any distance; when the air becomes moist, the pappus 

 closes up and the fruit falls to the ground. A pappose composite fruit under proper meteo- 

 rological conditions can be blown many hundreds of miles, thus doing away with the neces- 

 sity of postulating land bridges, in order to account for the presence of the Compositae on 

 oceanic islands. This is an important point, because this family is almost certainly of recent 

 origin. [See also Bot. Absts. 2, Entry 75.] — H. C. Cowles. 



265. Stakman, E. C, and M. N. Levine. Effect of certain ecological factors on the 

 morphology of the urediniospores of Puccinia graminis. Jour. Agric. Res. 16:43-77. Jan., 

 1919. — An attempt to ascertain whether the structure of the urediniospores of biologic forms 

 of Puccinia graminis changes readily in response to environmental conditions. It is con- 

 cluded that these biologic forms are as constant morphologically as they are parasitically, 

 and that the morphologic differences between them are as considerable and as distinct as 

 between many established species of fungi. The morphologic stability of a biologic form is 

 exhibited in the constancy of size, shape, and color of the urediniospores; oat stem-rust 

 (Puccinia graminis avenae) is an exception in that the urediniospores are very plastic in 

 respect to shape and size. [See Bot. Absts. 2, Entry 1081. Also abst. in Exp. Sta. Rec. 

 40; 641-642. 1919.]—//. C. Cowles. 



266. Stevens, O. A. The panurgine bees of North Dakota and a new Epeolus. Canadian 

 Entomologist 51: 205-210. 1919. — A list of the flower visiting bees, together with the names 

 of the plants at whose flowers they were found. The locality and dates given for the collec- 

 tion of the bees give also an index to the flora and the time of blooming of the species cited. 

 Petalostemon villosum is reported to occur only near Sheldon, whereas P. oligophyllum and 

 P. purpureum are common throughout the state. — Wanda Wenigcr. 



267. Tischler, G. Untersuchungen fiber den anatomischen Bau der Staub- und Frucht- 

 blatter bei Lythrum Salicaria mit Beziehung auf das "Illegitimitatsproblem." [Studies on 

 the anatomical structure of the stamens and pistils of Lythrum Salicaria with relation to the 



