rEBEUAEY 15, 1907] 



SCIENCE 



269 



which live parasitieally upon the primroses 

 through part of their development. This 

 relates both to ring-shaped and to simple 

 faseiations. 



Experiments upon the heredity of fascia- 

 tion prove that in these forms the seed of 

 normal plants produces as many flat stems 

 as the seed of banded plants. In the 

 (Enotheras the phenomena leading to fas- 

 ciation are those of traumatism. 



A Recording Evaporimeter: Burton Ed- 

 ward Livingston, Desert Botanical 

 Laboratory. 



The author describes and exhibits a 

 newly- devised instrument for studying the 

 daily march of the evaporation rate. It 

 consists of a porous clay cup filled with 

 distilled water and connected with a reser- 

 voir by a tube in which is placed an elec- 

 tric valve. A U-tube mercurj^ contact is 

 provided, by which an electric current 

 flows to open the valve when a cubic centi- 

 meter of water has been evaporated from 

 the porous cup and thus removed from the 

 instrument. The same column of mercury 

 makes a second contact and causes the 

 valve to close when a cubic centimeter of 

 water has flowed into the apparatus from 

 the reservoir. An electric pen, drawing 

 a continuous horizontal line upon a paper 

 slip carried on a daily rotating drum, is 

 raised slightly each time the valve is 

 opened, and thus a short vertical line is 

 drawn upon the record for each cubic 

 centimeter of water evaporated. The 

 spacing of these lines of course constitutes 

 a record of the varying time intervals re- 

 quired to evaporate ttat volume. This in- 

 strument is available for recording the rate 

 of loss of water, or of any liquid which 

 can be used with a glass stop-cock, from 

 any given container. For example, it can 

 be used to produce a recording potometer 

 for experiments upon plant transpiration. 



The following papers were read by title 



owing to the absence of the authors when 

 called for: 



A Composite Lycopod Type from the 

 Devonian: David White, U. S. Geolog- 

 ical Survey. 



This paper describes the i*emarkable 

 fossil tree trunk illustrated in the New 

 York Geological exhibit at the American 

 Museum of Natural History. The fossil, 

 which is extraordinary for its size and com- 

 pleteness, is very important systematically, 

 since it combines certain features that 

 serve to distinguish the later Lepidophytic 

 groups. Most conspicuous of these are the 

 Sigillaria form of leaf cushion in the lower 

 part and the Lepidodendron form in the 

 upper part. The fossil is one of the more 

 highly developed representatives of an an- 

 cestral type Archceo'sigillaria. 



Ryhridization a Factor in Migration and 



Competition: E. N. Tkanseau, Alma 



College, Michigan. 



The increasing list of plants which form 

 Mendelian hybrids by cross pollination 

 with closely allied species and varieties 

 necessitates the consideration of pollen dis- 

 semination in estimating the mobility of 

 such species. The ease with which vari- 

 eties of corn may be dispersed through 

 pollination is a familiar example. Such 

 hybrids are uniform in the first generation, 

 but in the second (F^) are resolved and 

 produce some pure individuals of each 

 parent type. A newly arisen variety of 

 a widely dispersed species may by this 

 means have its mobility greatly increased 

 beyond that due to seed and vegetative 

 propagation alone. 



Competition in nature may involve sev- 

 eral generations. In such cases factors 

 other than the purely physical must be 

 taken into account. The ability of a newly 

 arisen variety to form Mendelian hybrids 

 carries with it the chance, of being carried 

 over unfavorable seasons in the heterozy- 



