SELECTED NOTES. 185 



thus exhausting the protoplasm of the cells. After the mycelia 

 have obtained a lodgment and ramified through the intercellular 

 spaces of the potato, bi-anches are pushed out through the stomata 

 on the underside of the potato leaves, and on the ends of these 

 the gonidia are formed (Fig. i,^). These branches are remark- 

 able in form, resembling a string of beads. They, as well as the 

 gonidia at their ends, are white, and give a hoary appearance to 

 the diseased leaves. 



The resting spores of this fungus were discovered by Mr. 

 Worthington Smith. Those of a similar kind of fungus, Cytopus 

 candidus, are copied from De Bary's figure in Fig. 6. Those seen 

 in the slide are represented at Fig. 3. Two kinds of spores seem 

 to be present — a few large, light-brown ones and a number of 

 small, dark-coloured ones, I presume the latter are gonidia and 

 the former oospores. Fig. 5 shows the mode of fecundation 

 of the oospores in Cytopus. 



I have a few leaves of the potato with the disease on them in 

 my possession ; on these I notice some small, round, rose-coloured 

 bodies which puzzle me. C. H. Waddell. 



As to the restifig spores of the potato disease, they will be seen 

 best by day-light illumination and a J-inch o.g. There are two 

 schools : — First, those who believe that the mycelium lives all the 

 winter in the tuber, grow up in the summer, and thrives as the 

 plant thrives, and appears through the stomata. The second 

 school is of those who hold that the harm is in the resting spore. 

 This is the product of last year's disease, produced in exhausted 

 seeds and intercellular structures, in decaying potatoes and plants, 

 among manure, or in fields. It is produced by the union of pro- 

 toplasms of two cells. An interesting article on this subject will 

 be found in the English Mechanic of May, 1881. C. P. Coombs. 



Larva of Stratiomys chamseleon (Plate X ). — This is a dipter- 

 ous larva, common enough at Sheerness, and I daresay in other 

 parts of the country. It is a repulsive-looking object, that floats 

 inertly on the surface of the water in ditches and ponds. One 

 might easily think it inanimate, but a touch with a stick causes it 

 to twist and writhe for a moment ; it then relapses into a quiescent 

 condition. This creature is roughly portrayed in PI. X., Fig. i. 

 It is the larva of a handsome fly, Stratiomys Chamceleon. There 



