Fawcett: An Important Entomogenous Fungus 165 



the growth of these fungi, fair success in checking the whitefly 

 has been attained. 



Development of the Fungus 



The fungus as it develops upon a larva of the whitefly forms a 

 chocolate-brown (No. lo, Saccardo's Chromotaxia) stroma (pL 

 28, f. 2), which to the unpracticed eye looks like the citrus red 

 scale (Chrysomphalis Aonidum). A good description is given 

 of this stage of the development of the fungus by Webber (2) as 

 follows : " The hyphae develop in the body of the insect, burst 

 out around the edges of the scale, and gradually grow up over it. 

 In the early stage they form a brown, compact layer around the 

 edge of the larva. As the fungus develops, the hyphae entirely 

 cover the larval scale, forming a dense, hard, and smooth stroma. 

 The mature stroma is compressed-hemispherical, frequently having 

 a slight depression in the apex over the center of the insect, where 

 the hyphae come together as they spread from the edge of the 

 scale in their development. The hyphae which make up the body 

 of the stroma, are light brown, very tortuous, and but slightly 

 branched. Those in the body of the insect are of similar char- 

 acter, but a much darker brown. From the base of the stroma a 

 ground mycelium, or hypothallus, spreads out in all directions on 

 the surface of the leaf, forming a compact membrane near the 

 stroma, but becoming gradually dispersed into separate filaments." 

 In the later development of the fungus, the separate filamants 

 spoken of by Webber as spreading for a distance of one half 

 inch, grow out over the entire surface of the leaf, branching only 

 sparingly and infecting every larva present. They extend also 

 around the edges and over the upper surface of the leaf. These 

 filamentous hyphae are colorless to slightly tawny with age. 

 They are only occasionally branched, forming a loose, incon- 

 spicuous mycelium over the surface of the leaf. On the upper 

 surface of the leaf, on short lateral hyphae, are borne the sporo- 

 dochia, which are 60 to 90 /x in diameter. ■ These consist of an 

 aggregation of conidia-like, inflated, spherical cells, 12-18 in 

 diameter. From near the place of attachment of the sporo- 

 dochium, there radiate 3 to 5 hypha-like appendages, which are 

 150-200^11 long by 5-8 /X wide, and are one- to three-septate (pL 



