Febbuaby 12, 1909] 



SCIENCE 



269 



diameter, but readily regain their form. The 

 cilia continue to move even after the sperm has 

 penetrated the egg, but the nucleus soon slips 

 out from the cytoplasmic sheath and moves to- 

 ward the egg nucleus. 



Some details in the transformation of the 

 blepharoplast into the spiral band, as well as 

 details in the origin and development of cilia, 

 are better shown in Ceratozamia and will be 

 treated in greater detail in the forthcoming paper 

 on that genus. 

 Further Studies of (Enotheran Cytology: Dr. R. 



R. Gates, University of Chicago. 



In a recent paper' I described the method of 

 chromosome reduction in CEnothera, using 0. 

 rubrinervis and several of the other mutants as 

 types. I have since examined the various stages 

 of reduction in the wild 0. Mermis and in 0. 

 IcEvifoUa, and the observations confirm in prac- 

 tically every detail the results recorded in that 

 paper. In both of these forms the chromosome 

 number is fourteen, the reduced number being 

 seven. 



The essential points in the method of reduction 

 may be briefly stated as follows: 



After synapsis a single thick spirem is finally 

 formed, which breaks into a chain of fourteen 

 chromosomes lying mostly attached end to end. 

 These do not always pair with each other, but 

 frequently lie unpaired on the spindle. In the 

 heterotypic mitosis half of them pass to each 

 pole. Each divides during the later stages of 

 this mitosis, and the halves are separated by the 

 homotypic mitosis. The first mitosis thus sepa- 

 rates whole chromosomes and the second mitosis 

 the (probably) longitudinal halves of these. The 

 chromosomes become so nearly globular that the 

 direction of this split is not easily determined. 



On account of the weakness of the attraction 

 between homologous chromosomes at the time of 

 pairing, many of them lie unpaired on the hetero-" 

 typic spindle ; and this allows of occasional irregu- 

 larities in their distribution. Such irregularities 

 provide a possible basis for the origin of mutants 

 having the same number of chromosomes but lack- 

 ing certain groups of characters, provided, of 

 course, that the chromosomes are qualitatively 

 different. 

 The Type of the Genus Cactus: Dr. J. N. Rose, 



U. S. National Mviseum. 

 Edaphic Conditions im, Local Peat Bogs: Dr. G. 



P. BiJENS, University of Michigan. 



^ " A Study of Reduction in CEnothera rubri- 

 nervis," Bot. Qaz., 46, 1-34, 1908. 



Beginning with the open water, the plant socie- 

 ties usually found in the peat bogs near Ann 

 Arbor are the aquatic, bog-sedge, bog-shrub, tam- 

 arack, maple-poplar and willow or marginal socie- 

 ties. A study was made of the distribution of 

 these societies at different lakes and records were 

 made of the variations in the edaphic factors in- 

 fluencing the different societies. 



The data obtained indicate quite clearly that 

 the position of the peat deposit is dependent upon 

 the depth of the water and shape of the shore of 

 the original lake and not upon the direction of 

 the prevailing winds, as has been supposed. 



Of the edaphic factors, the position of the water- 

 table in the various areas is the most important. 

 This is subject to wide variations. In the summer 

 of 1905, April 24 to August 5, the variation under 

 the different societies was as follows: bog-sedge, 

 cm.; bog-shrub, 17 cm.; tamarack, 31 cm.; 

 willow or marginal society, 95 cm. In these 

 outer areas fungi and bacteria can work to greater 

 depths, changing the nature of the soil and ren- 

 dering it capable of holding more and more avail- 

 able water, or in other words less xerophytic. 



Continuous temperature records also show that 

 the marginal areas are less xerophytic than those 

 nearer the open water. 



Stomata and Transpiration in Tradescantia 

 zebrina: Dr. B. E. Livingston, Desert Botan- 

 ical Laboratory. 



The purpose of this study is to determine as 

 well as possible to what extent the stomata are 

 influential in causing the transpiration rate to 

 be relatively greater by day than by night. By 

 measuring the stomatal pores and calculating the 

 relative diffusion capacities for night and day, 

 it is found that this capacity in the daytime is 

 about 2.6 times as great as in the night. The 

 influence of the evaporating power of the air in 

 this connection varies, of course, with weather 

 conditions. The greatest difference observed 

 shows an evaporating power for the day of 6 

 times that of the night. The smallest difference 

 shows a ratio of 1.92. An attempt is made to 

 calculate the transpiration ratio (day to night) 

 by multiplying the evaporation ratio by the ratio 

 of diffusion capacity. The result of this appar- 

 ently shows that with direct sunlight the cal- 

 culated transpiration rate for the day is too low, 

 while with diffuse light it is too high. An average 

 of nine tests with diffuse light shows the actual 

 transpiration ratio to be 0.76 of the calculated, 

 but individual tests showed a close approximation. 

 The conclusion is that, with diffuse light, the 



