4 ¥ m—'& M tfi 4,'^ cj m % 



IV. Morphology of the Causal Fungus. 



The causal fuiiL^us, ]\R[a»ipsu)-a liniperda (Köhn.) I'ai.m is an autoecious 

 I^umelamijsoia and has tlie f<)Ilouin<j four spore-forms, viz. i) Spermogonium 

 (Pyctiidiimi)— Sperniatium (Pycnospore), 2) Aecidium (Accium) — Aecidiospore 

 (Aeciospore), Uredosorus (Urcdiniiim)-Uredospore (Urediniospore) and 4) Teleu- 

 tosoriis (Tclitini) — Teleiitospore (Teh'ospore). 



A. Spermogonial stage. 



I. Spcrntfls;ominn. Spermogonia are produced generally on young seedl- 

 ings when they are infected by the sporidia of the teleutospores of the fungus. 

 But they never appear alone, being always followed by the formation of the 

 aecidia apparently on the same mycelium. They occur on both sides of the 

 foliage as well as cotyledonous leaves and occasionally on the stems. These 

 spots are round and convex above, and when produced on the stems, cause hy- 

 pertrophy of their host tissues, and sometimes a swelling at the point of pro- 

 duction. The spermogonia are rather inconspicuous and pale-yellowish in colour. 

 Several of them may occur in a close group in the discoloured spot. They 

 are formed under the epidermal cells or somewhat sunk within the mesophyll 

 of the host tissue. The spermogonium is a flattened flask-shaped body walled 

 in by a large number of slender orange-coloured hyphae, and without ostiolar 

 filaments at its opening or mouth. Its size is 97.2 to 162. u in breadth and 

 63.0 to 93.6 n in height. Sometimes the spermogonium is formed of merely 

 a diffused layer of spermatiophores without a definite flask-shaped structure. 



3. SpcrmaticpJiore and spermatiiim. The spermatiophores are formed from 

 rectangular basal cells which are arranged in regular series at the base of the 

 spermogonium. These are septate, branched, colourless and slightly swollen at 

 the base. These spermatiophores differ from the unbranched non-septate ones 

 of Phragmidiitm violaccitm (Schultz.) Wint. and Gymnosporangium clavariae- 

 fonnc (jAcy.) DC described by H. \'. Black.m.\n'' in that they are usually 

 divided into two to four, each of which puts out a finger-like process from its 

 upper end on whose tip a single spermatiiim is produced. According to Fromme*^, 



1} Ann. Bot. XVIII, p. 323-373 (i904) 

 2) I. c. 



