November 12, 1915] 



SCIENCE 



683 



sterility in Plants and its Inheritance: A. B. 

 Stout. (Introduced by N. L. Britton.) 

 The different types of sterility are discussed as 

 a basis for the presentation of data on the phe- 

 nomena of self and cross sterility involving physio- 

 logical incompatibility. The evidence pertain- 

 ing to the behavior and inheritance of this type 

 of sterility in the flowering plants is summarized 

 and original data presented giving the results of 

 controlled self and cross pollinations with Cicho- 

 rium Intyius, which involve nearly 500 plants and 

 125,000 individual flowers. The existence of self 

 and cross sterility within this species is estab- 

 lished, and the appearance of self -fertile plants js 

 reported. Progenies of self-fertile plants have 

 been studied into the third generation exhibiting 

 ■with respect to self and cross sterility very ir- 

 legular behavior and most sporadic inheritance. 



Becent Explorations in the Cactus Deserts of 

 South America: J. N. EosE. (Introduced by 

 N. L. Britton.) 



The field work in connection with the cactus in- 

 vestigation of the Carnegie Institution of Wash- 

 ington contemplated a study of the deserts of not 

 only North America but also of South America, 

 the latter of which had never been thoroughly and 

 consecutively explored. Two seasons have been 

 given to South America, where an enormous 

 amount of material has been gathered. The three 

 following great deserts have been explored: First, 

 the desert of western Argentina. This includes all 

 of western Argentina. It resembles in its com- 

 ponent parts the deserts of Arizona. Second, the 

 desert of central Brazil. This is composed of the 

 western- parts of the states of Bahia and Pernam- 

 buco. It is very similar to the desert region of 

 Santo Domingo, and the typical genera are nearly 

 all West Indian. Third, the desert of Peru and 

 Chile. This comprises all of western Peru and 

 northern Chile. Its flora is the most distinct of 

 any of the South American deserts. 



Some Factors Affecting the Inheritance Batios in 

 Shepherd's Purse: Geo. H. Shull, (Introduced 

 by Chas. B. Davenport.) 



The Bespiratory Batio of Cacti in Belation to 

 their Acidity: Herbert M. Richards. (Intro- 

 duced by E. A. Harper.) 



Some Studies in Morphogenesis : E. A. Harper. 



Can We Otserve Organic Evolution in Progress? 

 Herbert S. Jennings. 



Orthogenesis in Plants: John M. Coulter. 



The gymnosperms furnish the best illustrations 

 among plants of what is caUed progressive evolu- 

 tion, or orthogenesis. Many lines of advance can 

 be traced in unbroken series from the Devonian 

 to the present time, involving structures that have 

 been assumed to be beyond the influence of ex- 

 ternal conditions. Three such lines are used as 

 illustrations. (1) The Egg. — In the history of 

 gymnosperms there is a gradual shifting of the 

 time of appearance of the egg in the ontogeny of 

 the gametophyte. In the most primitive forms the 

 eggs appear at the full maturity of the game- 

 tophyte. An unbroken series can be traced, rep- 

 resenting an earlier appearance of eggs, extending 

 from full maturity of the gametophyte, to very 

 early embryonic stages. Experimental work upon 

 sexuality in plants has shown that the appearance 

 of gametes is in response to certain conditions of 

 metabolism, and these conditions are associated 

 with minimum vegetative activity. Any change 

 of conditions shortening the period of vegetative 

 activity would thereby hasten the appearance of 

 eggs in the ontogeny of the gametophyte. This 

 is exactly the result that, in the case of gymno- 

 sperms, would follow the differentiation of the 

 year into definite seasons. The conclusion is that 

 orthogenesis in this ease holds some relation to the 

 evolution of climate. (2) The Proembryo. — A 

 similar illustration of progressive evolution is 

 offered by the earlier and earlier appearance of 

 wall-formation in the development of the pro- 

 embryo, until the stage of free nuclei is elimi- 

 nated. Since the progressive changes in the ap- 

 pearance of eggs and the development of the 

 proembryo in general proceed pari passu, the in- 

 ference is that they are both responsive to the 

 same changing conditions. (3) The Cotyledons. — 

 Eecent work has shown that the number of coty- 

 ledons is also a response to conditions affecting 

 vegetative activity. Among the causes that de- 

 termine the progress from polycotyledony or di- 

 cotyledony to monocotyledony, a conspicuous one 

 is the rate of growth of the subsequent members 

 of the embryo, and this rate is a response to con- 

 ditions for vegetative activity. The general con- 

 clusion is that the phenomenon of orthogenesis 

 among plants is to be explained, not as the result 

 of an " inherited tendency, ' ' but as a continuous 

 response to progressive changes in the conditions 

 of vegetative activity. 



Investigations Becently Conducted in the Wolcott 

 GibTjs Memorial Laboratory: Theodore W. 



ElCHARDS. 



The Life of Badium: B. B. Boltwood. 



