RECENT ADVANCES IN SCIENCE 457 



the breaking-down of the xylan taking place gradually and the 

 furfurol-yielding material increasing the longer the extract is 

 allowed to act. The author therefore considers that the fungus 

 contains an enzyme, xylanase, which hydrolyses xylan to 

 xylose. 



In the first of a series of papers on the physiology of para- 

 sitism, Brown (Ann. Bot. 29) describes experiments made with 

 an extract of the fungus Botrytis cinerea, finding that the 

 action of the extract on plant tissue is twofold — action on cell- 

 wall leading to disintegration of tissue and action on protoplast 

 causing death. The extract can be deactivated by heating, 

 by mechanical agitation, and by neutralisation with alkali, 

 but though the extract is acid, if any special lethal substance 

 is present it must be of colloidal nature ; the only active sub- 

 stance present is apparently an enzyme which causes macera- 

 tion mainly by solution of the middle lamella of the walls, 

 and that it is responsible for the lethal action is suggested by 

 the fact that death of the cells occurs either by direct action 

 of the enzyme on the protoplasmatic membrane or indirectly 

 through the action on the cell-walls. As an expected corollary, 

 it is found that the ability of certain tissues to resist the action 

 of the fungus extract depends upon the special properties of 

 the walls. 



Morphology. — Burlinghame (Bot. Gaz. 60) has followed up 

 his detailed study of the structure and development of the 

 conifer genus Araucaria by an elaborate discussion of the origin 

 and relationships of the araucarians, including some well-timed 

 remarks on the study of phylogeny in general and that of the 

 gymnosperms in particular. He points out that the science of 

 phylogeny has fairly adequate and reasonably trustworthy rules 

 of evidence ; that the degree of relationship is most clearly 

 indicated by a detailed and accurate comparison of all the 

 structures of the plant in all stages of development, and is 

 roughly proportional to the number and exactness of the re- 

 semblances ; that direct comparisons should be checked when 

 possible by the geological record, and may be supplemented by 

 the less reliable evidence afforded by the presence of presumably 

 vestigial structures in primitive regions and by recapitulationary 

 phenomena. As to the gymnosperms as a whole, he considers 

 the resemblances among these to be so strong as to preclude the 

 probability of their being polyphyletic, and that since the 

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