ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 629 



been very prevalent during both 1884 and 1885. If a plant having this 

 disease be examined closely, both surfaces of the leaf will be found to be 

 covered with minute brown or blackish specks, as fine as pin points, their 

 great abundance giving the rusty colour. The vegetative threads of the 

 fungus are not visible, being concealed in the tissues of the lettuce. It is, 

 therefore, an endophytic species. 



Lettuce Mildew. — This fungus, Peronospora gangliformis dBy., first 

 appeared in irregular patches half an inch or more across on both surfaces 

 of lettuce leaves. The vegetative threads of the fungus grow within the 

 leaf and only come to the surface to form spores. 



Rotting of Cherries and Plums. — Von Thiimen considers this fungus 

 (Oidium fructigenum S. & K.) to be perhaps the most noxious and de- 

 structive of all kinds that occur upon fruit. The fungus consists of colourless, 

 much branched and septated threads permeating the tissue of the fruit. 

 The fruiting threads consist of short sections, each a little more swollen as 

 they approach the ends of the threads where the sections are elliptical. 



Disease of Clover-leaf Weevil. — In the latter part of May, great numbers 

 of pale-gi'een larvae, nearly an inch long, were found clinging to the grass 

 and clover of the meadows, apparently dying from the attack of some 

 fungus. Dissecting a sick larva before death has occurred, a close net- 

 work of fungoid threads will be found among the muscles which line the 

 wall of the body. They are profusely branched, colourless, without septa, 

 the contents finely granular, and wdth or without vacuoles, or clear spots, 

 of variable size. This mycelium grows rapidly, and soon encroaches upon 

 the body-cavity of the insect, encompasses the various organs, finally absorb- 

 ing the juices and filling up the body with a solid mass of the fungus. 

 The spores are formed at the end of each mycelial branch ; some of the 

 branches, however, are enlarged and sterile. The spores are oblong, rounded 

 at both ends, one-celled, with thin walls and colourless granular contents, 

 and are comparatively large. The fungus is Entomopldhora Pliytonomi 

 Arth. 



In his Eeport for 1886, Mr. Arthur* deals further with the question of 

 plant diseases. The following is the order of topics :— 



Potting of Tomatoes. — Another year of observation on tomatoes 

 strengthens the opinion that the rotting of the fruit is not brought about 

 by a single agency, but by several, sometimes combined, but more usually 

 acting independently. The objects of the note are to point out that the 

 soft rot, chiefly affecting ripe fruit, must be discriminated from the brown 

 or black rot affecting green fruit. Probably Dr. Halsted is correct in 

 referring the decay in green fruit to Cladosporium fulvum. 



Disease of Clover-leaf Weevil. — Further study of Entomophthora Pliytonomi 

 Arth. reveals the fact that when the spores are germinated upon the surface 

 of water they take on a different development. Instead of at once producing 

 mycelium, they send out a short slender pedicel from one side, which bears 

 a solitary minute spore. The minuteness of these secondary spores, and 

 their aerial formation, makes it evident that they serve for long distance 

 transportation by wind. 



Strawberry Mildew. — This fungus, Sphserotlieca Castagnei Lev., produces 

 a delicate white cobwebby growth, which overspreads the plant attacked. 

 Later in the season, the resting or winter spores are formed in minute 

 globular spore-cases, which are first yellow, then change to black as they 

 ripen. 



* Eep. of Botanist to N. York Agricultnml Experimental Stat., Geneva, N.Y., for 

 1886, New York, 1887. 



