Royal Microscopical Society. 217 



IV. — The supposed Fungus on Coleus Leaves; and also Notes on 

 Podisoma fuscum and F. juniperi. 



By Henry J. Slack, F.G.S., Sec. E.M.S. 



{Read hfort the 1!oyai. Micuoscopical ISociEXi', April 3, ISTli.) 



Plate XVIII. 



A SHORT time ago ]\Ir. Eeeves showed me a slide exhibiting a sup- 

 posed fungus on a leaf of a Coleus plant, and said to grow inside 

 its tissues. A brief examination led to a doubt whether the sup- 

 posed fungoid objects were inside and not on the surface ; and having 

 a stock of the plants of various colours, an examination was com- 

 menced with a view to see how far the statements and opinions of 

 two letters, written by Mr. Howse to the ' Journal of Botany,' * 

 could be established. 



It will be seen that Mr. Howse speaks of boiling the leaves in 

 potash, and this will account for his results diifering in every 

 important particular from those described in this paper, and which 

 were arrived at by a careful avoidance of any process that would 

 change the character or apparent position of the leaf structure, or 

 the supposed fungoid bodies. 



In the first place a number of leaves were taken from Coleus 

 plants of various colours, and carefully examined in their natural 

 state, both by transmitted and reflected light. It became apparent 

 that every leaf, whatever its age or tint, exhibited, chiefly if not 

 entirely on the under surface, a number of globular bodies of a 

 beautiful yellow colour, highly translucent and refractive, most 

 of them marked with a cross hke that impressed upon the well- 

 known cross bun. These bodies differed in hue from any yellow of 

 the leaf, and they were distributed pretty uniformly without any 

 regard to the variegations of the leaf-colouring matter. From 

 damaged specimens it was obvious they were the bodies alluded to 

 by Mr. Howse. The colours of these bodies, when looking healthy, 

 and well filled with their refractive matter, varied from rich topaz 

 to a pale sherry tint, and they ghttered hke jewels when well lit 

 up. Empty cells had a rude resemblance to a mushroom in form, 

 with a stout stem and a round head marked with the cross, but the 

 texture did not look in the least fungoid, nor could any mycehum 

 be discerned in or on the leaves. 



It was also found that leaves of last year's growth and those of 

 this year had the same objects upon their under surfaces, and 

 pretty much in the same state, except slight varieties of colour or 

 occasional appearances of having withered. In no case out of 

 dozens of leaves taken from many distinct plants, could anything 



* Jan. 7, 1872, p. 23, aud March, 1872, p. 72. 



