388 SUMMARY OF CURRENT RESEARCHES RELATING TO 



bacterial infiltration extends. His description of the organisms agrees 

 closely with that of Koch, but he observed that the extremities of the 

 rods frequently presented a knob-shaped or wedge-shaped enlarge- 

 ment. They were very rarely united in pairs, and never massed in 

 the so-called zoogloea form. He corroborates their characteristic of 

 resistance to the ordinary methods of tinting, and only succeeded in 

 bringing them into distinct view by dilute alkalies. In a postscript 

 Baumgarten adds that he has succeeded in finding the same organisms 

 in human tubercle. The pathological importance of the discovery of 

 the proximate cause of this frightful scourge of the human race cannot 

 be over-estimated, nor is it possible to foretell the practical results to 

 which it may lead. 



Lichenes. 



Structure and Development of the Apothecia of Lichens.* — 

 The well-known structure of the apothecium of lichens described by 

 Stahl is taken from the Collemacege, where it is a product of an act of 

 impregnation performed by the spermatia. The female organ or 

 carpogonium here consists of two parts, a lower coiled portion, the 

 ascogonium, and an upper multicellular filament, the trichogyne, 

 through which impregnation by the spermatia takes place. After this 

 process the trichogyne dies, and a fibrous tissue springs from the asco- 

 gonium, composed of the asco-filaments which later develope into the 

 asci ; these are therefore the product of the fertilized ascogonium, 

 with which the paraphyses have no direct connection. 



Since the Ascomycetes vary greatly in the mode of development 

 of their fructification, it is to be expected that a similar variation 

 should exist in the development of the ascogonium of lichens, espe- 

 cially in those genera which do not possess a spermogonium. G. 

 Krabbe has investigated this subject in detail, with special reference 

 to the genus Sphyridium ; and the following are the main results 

 at which he has arrived. The author throughout uses as synonymous 

 the terms apothecium, fruit, fructification, and reproductive shoot. 



1. The genus Sphyridium exhibits a differentiation between the 

 apothecium resulting from an entire scale of the thallus or from a part 

 of one. The asco-filaments are the apices of ordinary hyphae, the 

 cycle of development of S. carnemn terminating with their production. 

 The production of the ascogonium is most probably independent of 

 any act of impregnation. 



2. In Cladonia two morphologically difierent structures exercise 

 the function of fructification in difierent species, viz. a, a pseudopo- 

 detium or modification of the thallus ; b, a podetium or new shoot com- 

 plete in itself (carpophore). Both podetia and apothecia are of 

 ascogenous origin. C. hacillaris and Papillaria are dioecious. The 

 following are the most important points regarding the power of 

 producing shoots possessed by the apothecium. 



3. The apothecium of lichens possesses the property of putting out 

 apothecial shoots at any spot, viz. a, from the hymenium, in Cladonia 

 Papillaria and Lecidea Pilati ; h, from the periphery of the paraphysal 



* Bot Ztg., xl. (1882) pp. 65-83, 85-99, 105-1(3, 121-12 (2 pis.). 



