HARDWICKE'S SCIENCE-GOSSIP. 



145 



GRAPHIC MICROSCOPY. 



By E. T. D. 



No. VII.— Cluster Cups : GEcidium quadrifidum. 



'HEN the micro- 

 scope opens a new 

 world for investi- 

 gation, an intelli- 

 gent observer 

 soon discovers 

 that his interest 

 does not pause at 

 mere admiration ; 

 a curiosity is 

 aroused, a wish 

 created to enter 

 deeper into the 

 physiological won- 

 ders involved. It 

 would be difficult 

 to touch any par- 

 ticular branch of 

 microscopy where 

 this desire is not 

 excited, but in the 

 contemplation of obscure and minute forms of vegeta- 

 tion it exists in a high degree. 



Although the Fungi seem to show unusual simpli- 

 city and homogeneity of structure, the great interest 

 they create depends on their most intricate com- 

 plexity, in connection with their reproduction ; and 

 when touching upon the life history of such a subject 

 as the present, a short and "popular" description 

 becomes insufficient ; most interesting technical 

 details may however be found in many papers 

 published in this journal during the last few years. 



Upon the leaves and stems of mint, gooseberry, 

 buckthorn, nettle, common spurge, and of many 

 herbaceous plants may be seen minute spots of a 

 bright orange colour ; the Peridia, or spore-bearing 

 receptacles of CEcidium, a genus of Uredinei (Conio- 

 mycetous fungi). These growths are parasitic within 

 the tissues of leaves, and the subject of the plate 

 is the fructification, the peridia, which have burst 

 through the epidermis of the leaf and appear as 

 "cups" split at the margins, a feature in classifica- 

 No. 235.— July 1884. 



tion) and containing the germinating spores ; found 

 within as a yellow, and in other cases, red or brown 

 powder. 



These fungi maybe observed in an early stage before 

 the emergence of the cup, and are discovered by 

 changes and deformity produced on the surface of the 

 leaves of the infected plant ; appearing as minute 

 elevations, or blisters, they increase in size and tension, 

 until the epidermis gives way and the developments 

 beneath burst through. The "cup," or peridium, is 

 then revealed, as an irregular sac, broken on the edge 

 in radiating fissures ; when ripe and curled back, it 

 forms an elegant microscopic object. 



If a perpendicular section of the cup and the parts 

 beneath be made, or the cuticle of the leaf carefully 

 peeled off, it will be found that the tissues of the 

 host are distorted by the growth of a filamentous 

 structure, the mycelium of the fungus which ramifies 

 among the intercellular passages, and in certain points 

 crowds into a compact mass, immediately beneath 

 the epidermis ; by the tension of these felted accumu- 

 lations the leaf splits, and giving way, a few filaments 

 push through the opening, forming the cupped spot, 

 the granular masses below escape, and eventually 

 develop the fructification. There is obviously neither 

 root nor leaves ; nothing exists as absorbents of 

 nourishment, but the interlacing fibres, penetrating 

 between the cells of the leaf (unlike the lichens, 

 which derive support solely from the air), these fungi 

 are entirely sustained by the organic substances 

 diverted from the necessities of the plant ; this 

 vegetative felty mass, mycelium or " spawn," is 

 branched and colourless when growing in the earth 

 or in vegetable structures or substances, but when ap- 

 pearing in decomposing fluids it forms cloudy flocks j 

 the reproductive fruit emanating from its various 

 conditions of habitat, is extremely diverse in appear- 

 ance, as may be seen in the mushroom, the puffball, 

 mildews, and smuts. 



In the GEcidiacei it takes the form of these minute 

 cups ; the spores within are in enormous numbers ; 

 seen in a perpendicular section, they are found 



H 



