272 



SCIENCE 



[N. S. Vol. XXIX. No. 737 



Phytophthora thalictri were found, but cultures 

 were not attempted, since the host had no peren- 

 nial parts from which infected tissue could be 

 taken. However, the oospores, not reported be- 

 fore, were found in the leaves. To account for 

 their absence in the potato mildew, especially in 

 artificial cultures, the writer suggested that these 

 fungi may have distinct sexual mycelia. This is 

 indicated by observations that the antheridia and 

 oogonia of the other two species seem to be borne 

 on separate mycelial threads. Recently the writer 

 again obtained pure growths of the lima bean 

 mildew, from which several hundred cultures have 

 been made in an attempt to solve this problem. 

 Cultures from mycelial growths, possibly mixed, 

 have so far always produced oospores. Petrie 

 dish separation cultures are now being made to 

 get cultures from single spores. If the theory is 

 correct, these should produce no oospores. 



Origin and Function of the Peridium of the 

 Rusts: Professor E. W. Olive, South Dakota 

 State College. By title. 



Observations on the Relation of Wound Parasites 

 to the Heartwood of the Affected Tree: Dr. P. 

 Spauldinq, Bureau of Plant Industry. 

 While studying various wood-rotting fungi for 

 the past few years there has been noted a very 

 apparent relation of the so-called "wound para- 

 sites " to the heartwood of the diseased trees. A 

 very striking instance of this was that of Fom.es 

 ribis occurring upon sassafras trees. In every 

 case examined this fungus was found attacking 

 the tree only in wounds where the heartwood was 

 exposed by some injury, such as the breaking of 

 a large branch, or the splitting of a branch from 

 the main trunk. Fames igniarius, as studied for 

 the past four years, upon beech, has been found 

 occurring in a similar manner. Hundreds of 

 blazed beech trees have been examined, and in not 

 a single instance was this fungus found growing 

 upon these blazes in the sapwood. On the other 

 hand, it was constantly found at wounds which 

 extended into the heartwood. Polystictus versi- 

 color, when attacking the heartwood of catalpa, 

 occurs, growing into the stubs of dead branches. 

 Such observations as have been thus far made 

 upon Fomes fraxinophilus when attacking white 

 ash show the same thing to be true, the attack 

 practically always being made through dead stubs. 

 Von Schrenk has also said that Fomes rimosus 

 attacks the heartwood of black locust, either by 

 entering through the dead stubs or through insect 

 burrows. The sapwood of black locust is com- 

 paratively thin, and it is safe to accept his im- 



plied statement that heartwood must be exposed 

 before this fungus attacks its host. 



Further Studies of the Anthracnoses : Dr. C. L. 

 Sheak and Miss Anna K. Wood, Bureau of 

 Plant Industry. 



Twenty-three forms of so-called Colletotrichum 

 and Olceosporium from the following hosts have 

 been studied since the writers' previous paper 

 was published: 1, Camellia japonica; 2, Caryota 

 rumphii; 3, Oinnamomum zeylanicum; 4, Citrul- 

 lus vulgaris; 5, Citrus limonum; 6, Citrus de- 

 cumana; 7, Citrus aurantium; 8, Coffea arabiea; 

 9, Costus speciosa; 10, Cucurbita maxima; 11, 

 CurcuUgo sp.; 12, Eriobotrya japonica; 13, Ficus 

 longifolia; 14, Kentia sp.; 15, Lathyru^s odoratus; 

 16, Ligustrum vulgare; 17, Maranta lineata; 18, 

 Musa sapientum; 19, Persea gratissima; 20, 

 Phormium tenaao; 21, Piper maorophylla; 22, 

 Pitcairnia corallina; 23, Psidium guajava; 24, 

 Rubus occidentalis; 25, Thea bohea. 



Pure cultures made from conidia from hosts 6, 

 16, 19, 24 and 25 produced both conidia and asco- 

 spores and both these forms of fructification have 

 been found on the host plants also. Cultures from 

 conidia from hosts 3, 20 and 21 have produced 

 both conidia and asei, but no ascogenous fructi- 

 fications have been found on the host plants them- 

 selves. On hosts 1, 2, 5, 7, 8, 9, 11, 12, 13, 17, 

 22 and 23, both conidia and ascospores have been 

 found. On hosts 4, 10, 14, 15 and 18 only conidia 

 have been found and the cultures from the same 

 hosts have produced only conidia. 



Cultures from a single conidium taken from 

 Persea gratissima carried through twenty-three 

 generations have shown considerable variation in 

 character of growth and development in diflTerent 

 generations. Cultures from a single aseospore 

 from the same source carried through seven gen- 

 erations have been quite uniform. The cultures 

 from conidia usually produced an abundance of 

 aeervuli followed by perithecia. The cultures 

 from ascospores produced no aeervuli except a 

 few very small ones in the first generation, but 

 scattered conidia and an abundance of perithecia 

 occurred in all. The aseospore cultures still 

 produce conidia and the conidia cultures still 

 produce asci. 



No morphological characters either in cultures 

 or under natural conditions have been found to 

 be sufficiently constant to justify the segregation 

 of species except perhaps in the ease of the cotton 

 anthracnose. The ripe rot fungus of the grape, 

 Olceosporium [Glomerella) rvfomaculans, repre- 

 sents fairly well the essential characters of all. 



