404 SUMMARY OF CURRENT RESEARCHES RELATING TO 



to tlie number of very many thousands. The effects of rain and dry- 

 ness, heat and cold, upon the number and kind of the atmospheric 

 germs drawn into the aeroscope are given statistically ; the months 

 and seasons are compared amongst themselves and with previous 

 years. Dr. Mi quel employs means for comparisons, and shows some 

 interesting coincidences, as the increase in the number of atmospheric 

 germs and the increase of the death-rate at certain times, though he 

 does not say they stand related as cause and effect. Long and 

 patient inquiry is necessary, and an unbiassed judgment in the 

 examination of this special point. It would be impossible in the 

 short sjiace we can devote to it to deal with the details contained iu 

 this excellent work, rej^lete with illustrations of different germs and 

 various forms of apparatus employed for collecting, sterilizing, and 

 ci;ltivating. Mention is made of the improvements in the apparatus 

 as the difficulties increased, and we believe that much more delicate 

 and elaborate instruments and selected cultivating fluids are now in 

 use for dealing especially with the bacterial element of the air, to 

 which much attention is at present being given by the medical pro- 

 fession, especially in relation to the bacillus of tubercle. 



It is to be regretted that a similar department is not created in 

 this country, which is supposed to lead in all matters connected with 

 hygiene, and that some basis upon which to carry out the objects 

 in view is not established by different governments in the hope of 

 attaining, if possible, to better preventive measures against zymotic 

 and contagious diseases. Such works as the present will lead us 

 nearer to the realization of more effective measures for the prevention 

 and extension of disease, whether of plants, animals, or man. 



Lichenes. 



Reproductive Organs of Lichens.* — The most recently published 

 part of Minks's ' Symbolfe licheno-mycologicae ' treats of the Hys- 

 teriacefe, Acrospermeae, and Stictidese. The author still maintains 

 his opposition to the view that a lichen is a compound organism, made 

 up of a fungus and an alga. 



On the asci and par<aphyses together Minks bestows the term 

 " thalamium " ; the " thecium " being that portion of the apothecium 

 which includes these organs. The structure of this portion of the 

 lichen may be referred to three different types: — (1) the asci and 

 paraphyses are both fertile hyphas, which, in the latter case, have 

 undergone arrest of dcveloimient ; and there are all intermediate stages 

 between the two. (2) The paraphyses are formed a shorter or longer 

 time before the fertile hyphBB. They are at a certain jjcriod indis- 

 tinguishable from the hyphee of the fundamental tissue of the fructifi- 

 cation, and there is here no true thalamium. To this class belong 

 the true Stictidese and the greater part of the Hysteriaceae. (3) 

 Certain genera exhibit an intermediate structure between the first and 

 second. 



* Minks, A., 'Symbolaj licheno-mycologicoe.' Part II. Cassel and Berlin, 

 1882. 



