PATHOLOGIC PLANT ANATOMY 



365 



an abnormal size by the omission of cell division. Under the influence 

 of a fungous parasite, Chytridium sphac ell arum, the apical cells of the 

 lateral branches of an alga, Cladostephus spongiosus, stop dividing and 

 enlarge into club-shaped swellings at their upper end. If specimens of 

 Padina pavonia, a siphonaceous alga, be inverted and are exposed to 



Fig. 143. — Drawings of rods and involution forms of Pseiidotnonas lumefaciens 

 from young tumors. A, B, Daisy on daisy; C, D, hop on red table beet; E, F, hop 

 on sugar beet. (After Smith, Brown, McCulloch, Bull. 255, U. S. Bureau of Plant 

 Industry, 1912.) 



light, their spiral edges uncoil and the cells of the apex enlarge into 

 vesicular form. The hyphae of the sterile mycelium of Rozites 

 gongylophora found in the fungous gardens of the tugging-ant, Atta, 

 show regular ball-like swellings on the ends of the hyphae. These 

 united into thick groups form the kohl-rabi growths which serve the 

 ants as food. 



