296 



The Plant World. 



own on fire-swept ground. The fire causes the opening of the 

 cones, and a new generation of trees arises from the seeds thus 

 released. 



Actual tests of the viability of the older seeds, however, 

 have been almost wholly wanting, but in the American Natural- 

 ist for November, 1909, Prof. W. C. Coker gives an account of 

 recent germination experiments with seeds of Pinus serotina. 

 In the neighborhood of Hartsville, S. C, the cones of this pine 

 were often found to remain unopened for ten or more years. In 

 the tests made last summer at the New York Botanical Garden 

 it was found that although the percentage fell off with increasing 

 age, a fair number of seeds as much as fourteen years old ger- 

 minated. 



Louise Hoyt Gregory (Bull. Torr. Bot. Club; 36; 1909) 

 reports as the result of her investigations of the effect of mechan- 

 ical pressure on the roots of Vicia faba that pressure up to as 

 much as 1400 to 2000 grams has no effect on the mitotic figure 

 or division wall of the root cells. With the same pressure, how- 

 ever, certain morphological changes, such as breaking up of the 

 plerome cells, splits in the periblem layer, and displacement in 

 both plerome and periblem, were noted. 



Fitting's recently published monograph on the conduction 

 of stimuli in plants, while adding little new to the subject, is a 

 valuable contribution, in that it brings into one volume, and 

 ably organizes, the extensive, but uncorrelated data on this 

 subject. Fitting's thorough acquaintance with the subject, 

 coupled with his evident broad perspective results not only in a 

 comprehensive treatment of the problem of stimuli and their 

 conductions, but remarks and suggestions regarding the relation 

 between these and other phenomena, as of growth and develop- 

 ment, makes the book a very suggestive one. 



The volume is divided into two parts. The first deals with 

 stimulation from external and internal sources. Among the 

 former are discussed stimulation due to touch as in Mimosa, or 

 Bryophytum; contact, and chemical stimulation, as in Drosera; 

 wound stimuli; and the various tiopisms which he distinguishes 



