March 24, 1910] 



NATURE 



example, the occasional sterility of the gills, which 

 consequently remain colourless in species normally 

 producing coloured spores, has already been discussed 

 in more than one text-book, and the conclusion arrived 

 at is identical with that advanced by Dr. Buller. 

 Cystidia are included in the category- of hair forma- 

 tions. Probably the definitions as to the origin of 

 hairs are various, but certainly true cystidia — not to be 

 confounded with swollen marginal cells — originate 

 from deep-sealed cells. 



Coming to the crucial point of research, the libera- 

 tion of spores, it is at once obvious that the author 

 attempts generalisations on too narrow a basis, as 

 proved by the following quotation : — 



• Excepting a few gelatinous species which require 

 further investigation, it is a general rule that in 

 Hymenomycete^ the hymenium is situated on the under 

 side of the fruit bodies." 



He has ignored, or does not realise, the exis- 

 tence of many hundreds of species included in the 

 Hymenomycetes where the hymenium is on the upper 

 surface of the sporophore, and pointing upwards, as in 

 Corticium, many species of Stereum, Hymenochaete, 

 Poria, Src, yet such species are as numerous and cos- 

 mopolitan in distribution as the species with which he 

 is acquainted. 



In the Agaricineae and the Polyporeae it is considered 

 that the position of the hymenium on the under- 

 surface of the sporophore has been primarily decided 

 as affording the greatest facility for spore dispersion. 

 The spores are very adhesive when fresh, hence to 

 secure successful liberation the gills or tubes must 

 occupy a vertical position, which is secured by the 

 rigidity of the sporophore. Gravity is the principal 

 orienting stimulus acting on the sporophore. The 

 spores on a basidium are discharged successively ; each 

 spore is shot out violently to a distance of about 

 iV mm., and afterwards falls vertically downwards. 

 Ihe horizontal projection of the spores necessitates 

 that gills should be placed at a certain distance apart. 

 The process of spore liberation is treated in detail. 

 Some very ingenious and interesting observations on 

 the rate of fall of spores are furnished, which, subject 

 to modification owing to their size, specific gravity, 

 and process of desiccation, ranges from o'3 to 60 mm. 

 per second. The specific gravity of spores is deter- 

 mined approximately by using heavy fluids contained 

 in a counting apparatus. In the genus Coprinus the 

 gills are usually stated to deliquesce, or melt into a 

 black, inky fluid, and it was generally assumed that 

 the spores were contained in this fluid. According to 

 Buller, however, the spores are shot off and fall as in 

 other Agarics, commencing at the margins, and when 

 a narrow zone of the gill is depleted of spores, the 

 naked portion of the gill is consumed by a process of 

 autodigestion. A most intei-esting account of the 

 means by which the spores falling from a fruit-body 

 may be seen by the use of a concentrated beam of ligh*^ 

 is given, but perhaps the most unexpected pheno- 

 menon explained is the fact that the sporophores of 

 certain fungi retain their vitality for years in a dried 

 condition, and, after the application of wet cotton- 

 XO. 2108, VOL. 83] 



wool, quickly revive and begin to shed their spores, a 

 process which continues for some days. 



It is estimated that the giant puff-ball produces 

 7,000,000,000,000 spores, also that only one spore out 

 of about 20,000,000,000 spores ever succeeds in produc- 

 ing a mushroom capable of reproduction. In addition 

 to the many valuable new discoveries and new theories 

 bearing on subjects previously investigated by other 

 observers, the book abounds with suggestions and 

 sidelights which cannot but prove of immense service 

 to future workers. 



Ten plates and numerous excellent figures in the 

 text are of much value in following and grasping 

 clearly the various points raised by the author. 



(2) Notwithstanding the extensive researches of 

 Frank, Bernard, and others bearing on the relation- 

 ship between fungi and the roots of phanerogams, 

 resulting in the structures known respectively as 

 ectotropic and endotropic mycorhiza, much yet remains 

 to be done before we are in a position to formulate the 

 significance of such combinations. Dr. BurgefT has 

 contributed considerably to our knowledge in this 

 respect, and has added many new facts bearing on 

 the nature and life-history of those fungi met with 

 in the roots of orchids. Fifteen different kinds of 

 fungi were isolated and carefully studied from pure 

 cultures. The majority of these produced asexual 

 reproductive bodies, mainly under the form of long 

 chains of minute conidia of the oidium t}-pe. No 

 higher form of fruit was observed, hence the systematic 

 position of these root-fungi yet remains to be deter- 

 mined. 



Wahrlich's view that certain of the fungi found in 

 the roots of orchids belonged to the genus Nectria 

 has not been corroborated by Burgeff. Sclerotia are 

 sometimes produced. On account of the general 

 resemblance of orchid fungi to those of Rhizoctonia, 

 Bernard placed all the forms he isolated from orchids 

 under the last-named genus. Burgeff, on the other 

 hand, has created a new genus — Orcheomycetes — for 

 the reception of his various forms, which are named 

 specifically after the host from which they were 

 isolated ; thus the form isolated from Ophrys apifera 

 becomes Orcheomycetes apiferae. The wisdom of 

 creating new generic and specific names for admitted 

 form-species is doubtful, more especially as the author 

 states that such names have no systematic importance 

 or significance. The group characters are based on 

 the behaviour and mode of growth of the fungus, as 

 a pure culture, on the substratum. The specific fea- 

 tures turn on the nature of the hyphae, form and size 

 of conidia, some of which are comparatively large, 

 and in some instances there are indications of the 

 formation of pycnidia. 



All the described forms are of endotropic origin, 

 truly ectotropic mycorhiza occurring only ver\- seldom 

 ia orchids. 



The question of nutrition in cultures was investi- 

 gated, and the important fact noted that no assimila- 

 tion of free nitrogen took place. All the species are 

 aerobic. 



The concluding part of the work deaU with the 



