302 



MYXOGASTPJC FUNGI. BLIGHTS OF CORN. 



duction of the spore, undergoes a change in its condition similar to 

 that already described, in the cells of Volvox (§ 198), and that the 

 Protoplasmic substance of the Amoeboid body thus formed extends 

 itself into diverging threads in a manner that strongly reminds us 

 of the sarcodic network of the Rhizopods. That such a resem- 

 blance should exist can scarcely be considered surprising, when it is 

 borne in mind that the Vegetable "protoplasm and the Animal 

 sarcode are essentially identical substances ; and that not merely 

 the network of inosculating threads of Gromia (Fig. 232), but the 

 circulation of particles constantly kept up in it, has its parallel in 

 the network of viscid Protoplasm which may be traced on the 

 internal wall of many Vegetable Cells (§§ 287-289), and which 

 exhibits the like continual movement of its constituent particles. 

 Thus, then, it may be considered that the observations of De Bary 

 tend to confirm those of Drs. Hartig and Hicks (§ 255, note) in 

 regard to the Amoeboid form which may be assumed by certain un- 

 doubtedly Vegetable products ; whilst if themselves interpreted by 

 the light of those phenomena, and by the undoubtedly Fungous 

 nature of the fructification of the Myxogastres, they indicate 

 nothing more than that the tribe in question affords a most remark- 

 able example of the same metamorphosis.* 



270. The parasitic Fungi which infest some of the Vegetables 



most important to Man as 

 furnishing his staple articles 

 of food, constitute a group 

 of special interest to the 

 Microscopist ; of which a few 

 of the chief examples may 

 here be noticed. The Mil- 

 dew which is often found 

 attacking the straw of Wheat, 

 shows itself externally in the 

 form of circular clusters of 

 pear-shaped Spore -cases (Fig. 

 173), each containing two 

 compartments filled with 

 sporules ; these (known as 

 the Puccinia graminis) arise 

 from a filamentous tissue 

 constituting its mycelium, 

 the threads of which inter- 

 weave themselves with the 

 tissue of the straw ; and 

 they generally make their 

 way to the surface through 



Fig. 173. 



Puccinia graminis. 



* Dr. De Bary's latest views on this subject, which are in accordance 

 with what is stated above, will be found in his contribution to Prof. 

 Hofmeister's "Handbuch der Physiologischen Botanik," Band ii. 

 p. 295. 



