VEGETATIVE REPRODUCTION. 



i8g 



set free by the rupture or by the solution of a portion of the 

 enclosing wall (fig. 140). They may begin to move before 

 the rupture of the wall, in accomplishing which their activity 

 may materially assist. They then work their way out and 

 swim freely in the water. After a time of movement they 

 usually lose their cilia, either withdrawing them into the 

 protoplasm or dropping them off, come to rest, and begin to 

 grow into a new plant. 



265. Non-motile spores are formed by all classes of land 

 plants without exception. They are often produced in great 

 profusion, especially by the fungi, the mosses, the ferns, and 

 the seed plants. 



266. Form and food. — Their form is exceedingly various. 

 Many are spherical or ovoid, while some are cylindrical or 



eo 



Fig. 141.— Part of a vertical section of a leaf of a willow, attacked by a fungus {Melainp- 

 sora salicina). eo. epidermis nf upper side lifted by the young teleuto-spores, t, de- 

 veloping from the spore-bed above the ends of the paHsade cells of the host {par) ; 

 eu, epidermis of the under side, broken rhrough by the spore-bed from which spring 

 uredo-spores, it, and paraphyses, />. eo will also finally be ruptured to set free t. 

 Magnified 260 diam.— After Prantl. 



even needle-shaped (figs. 141, 143, 166). Irregular forms, 

 also, are not uncommon. The same plant may produce at 



