230 PHYTOPHTHORA MEADll h, sp. ON HEVEA BRASILlENStS 



from the bud become flaccid, and all of them may be infected right down to 

 the growing point, their entire laminae and the embryonic tissue of the stem 

 being penetrated by the hyphae. 



In the majority of leaves that fall during the monsoon, the dull discoloured 

 spot on the petiole is more or less clearly visible, and it may occur on any part 

 of the petiole. It is usually from 1 to 4 centimetres long, and may be on one 

 side of or right round the petiole. Similar spots may be present on the petio- 

 lules of the leaflets. Sections reveal the presence of the hyphae in the tissues, 

 and they occur in a way very like those in the young stem. Hyphse are not 

 usually present on the surface of the spot when the leaf falls, but, when a 

 petiole is kept for one or two days in a moist chamber, they come to the surface 

 readily. Before the leaves fall, an absciss layer is formed at their point of 

 junction with the shoot. 



Amo.ig my notes is a record of having found Pht/tophthora on the inflores- 

 cence in a previous year, but the material has been mislaid. During the last 

 two flowering seasons, a search was made for it on several estates, but with 

 negative results, even though fruit-rot and leaf- fall were heavy during both 

 the monsoons, particularly so in 1917. By inoculation the flowers and their 

 stalks become infected readily by Phytophthom, but to decide whether this 

 occurs in nature needs further observation. 



Beneath the dull ashy-grey spot on the fruit, hypha; are found passing 

 along the intercellular spaces and sometimes into and through the cells as well. 

 The chlorophyll -grains become yellow, then also the protoplasm and cell- 

 walls. The cells lose their turgidity and come apart, and the intercellular 

 spaces become filled with water. This is the beginning of the soft-rot. In 

 fruits that have small spots, and in inoculated fruits, after two days this can be 

 quite clearly seen, but soon bacteria and hyphae of other fungi, especially 

 Fusarium, Coprinus, Nectria, and Botryodiplodia, appear in the tissues. The 

 soft-rot is begun by the Phytophthoro, and is helped on by the bacteria and 

 other fungi. All of these fungi are found commonly on the pericarp of healthy 

 fruits both before and after the endocarp has split and liberated the seeds, 

 and especially after the empty fruits have fallen to the ground. Seeds from 

 such fruits invariably germinate and grow into healthy seedhngs. These 

 fungi do not enter into the present problem, and work on them was stopped 

 after the Phytophthora was discovered. The mesocarp splits along 6 lines of 

 suture, and contracts at the edges away from the endocarp to a much greater 

 extent than in healthy fruits. The hyphae pass into the axis of the fruit either 

 downwards from the insertion of the fruit-stalk or inwards through the 3 shts 



