o^_|^ Keieratc. 



1. Density of colonies produces various effects with different species. 

 It sometimes inhibits pycnidial formation, resulting in naked spores, it 

 sometimes prevents development of color, it sometimes limits the size of 

 the colony, and sometimes is without effect. 



2. Density of mycehum sometimes cause spasmodic periods of rapid 

 growth and quiescence to follow one another, bringing about a zone-like 

 appearance in the culture. 



3. Variations such as presence and absence of setae, and presence and 

 absence of catenulate spores is thought to be due to variation in the 

 chemical composition of the supporting medium. 



4. "Light exerts little or no effect upon lineal growth." It may inhibit 

 pycnidial development or cause zonation in colonies. 



Other changes were noted but not analyzed. It seems to the reviewer 

 very unfortunate that no studies have been made with pure lines of fungi. 

 Until something is known concerning the limits of variation in fungi, the 

 value of breeding disease resistant plants is questionable. If fungi strains 

 can vary to a considerable degree on one host plant, then a comparatively 

 resistant plant may become inoculated through injury and afterwards 

 become susceptible through survival of the most virulent strain of the 

 varying parasite. E. M. East, Harvard University. 



Griggs, R. F., Juvenile kelps and the recapitulation theory. American 

 Naturalist 43 1909, pp. 5—30, 92 — 106. 



From his study of the four genera Rcnfrnvia, Lessoniopsis, Egrei^ia and 

 Hedophylliim in all stages of their development, the author contributes some 

 interesting data on recapitulation in plants. 



Jiciifracia shows a transition from a pithweb of simple polygonal cells 

 to the complex differentiations of the higher kelps such as Ncrcocyslis. 

 "Such plants must of necessity pass through the condition of Renfreivia in 

 order to attain mature structure." Further, "All of the young forms pass 

 through a period when the stijie is short as compared with the lamina. 

 In all which have been described [by the author] except Hcdophylliim, this 

 condition persists imtil a certain very definite period, after which the 

 stipe elongates rapidly. This condition is so similar to the adult stage of 

 Reiifravia that one is tempted to consider it as a recapitulation of such a 

 stage. But instead it may be only a necessary physiological adaptation 

 which the young plant undergoes early in its development in order to 

 provide a large photosynthetic area to furnish the foud for rapid growth." 



These facts among others appear to the author to justify the theory 

 of Morgan that recapitulation is not the repetition of adult characters 

 during ontogeny, but rather the repetition of embryonic stages similar to 

 those that the ancestors of the species possessed. Nevertheless he beheves 

 that organisms are subject to adaptation at any stage of their life cycles, 

 and that, even if many superfluous stages hav'e been discarded, there will 

 be a correlation between the individual life cycle and its ancestral history 

 which may — in certain cases — be very high. 



Since the botanists have lagged behind the zoologists in studies of this 

 character, the author makes a welcome contribution to the literature. 



E. M. East, Harvard University. 



