Pethybridge — On the Rotting of Potato Tubers. 555 



resemblance to P. erijthroseptica is much greater than to P. Cactorum. It is not 

 surprising that tlie details of the hyphae bearing the oogonia and the 

 antheridia are in some cases omitted in the figures in question, seeing that 

 even in P. eri/throseptica it is often hard to make them out with accuracy in 

 the later stages unless they have been clearly recognized in the earlier ones ; 

 and I look upon it as a matter of little moment that in these figures the only 

 hypha shown is apparently the oogonial one. 



What Coleman describes as the " fertilization tube of the antheridium," 

 which is seen in the figure reproduced, is, I think, more likely to be one of 

 the trabecula-like structures which I have already described for P. eri/thro- 

 septica on p. 545, and wliieh are illustrated in fig. 17, Plate XLIV. Should 

 my suspicions as to the real nature of the sexual organs in P. omnivora var. 

 Arecae prove on re-examination of his preparations by the author to be well 

 founded, he will probably concur in adopting the name' Phytophthora Arecae 

 for this species. 



A species (or perhaps more than one species) of Phytophthora is frequently 

 found in various parts of the tropics, causing a disease in Cacao. Eecently 

 von Faber (8) has given an account of this disease, and of the fungus which 

 causes it, in a paper in which the earlier literature on the subject is also dealt 

 with. The fungus has been assumed — on insufficient evidence, as von Faber 

 points out — to be identical with P. omnicora de Bary ; but von Faber him- 

 self leaves the question of the identity of the fungus he was dealing with an 

 open one. 



Maublanc, on the other hand, as Coleman' has already pointed out, was not 

 deterred by von Faber's hesitancy from utilizing the latter's description to 

 found on it a new species, P. Faberi, apparently without having seen the 

 fungus himself. This fungus produces oospores of about 45^ diameter chiefly 

 in the slime canals of the Cacao, but the oogonia and antheridia have not been 

 seen. 



A nearly allied fungus which attacks the Cacao, or possibly the same one, 

 has been described by Coleman^ under the name of Phytophthora Theobromae. 

 It is interesting to note that in this case well-marked parthenogenesis occurs ; 

 in fact, Coleman was unable to find a single antheridium. Parthenogenesis 

 is also of frequent occurrence in P. infestans. 



From what has been said it will be seen that apart from those species in 

 whicli the mode of sexual reproduction is unknown, or only imperfectly 

 known {P. Colocasiae, P. Thalictri, P. Nicotianae, P. Faberi, P. Theobromae, 



' Loo. cit., p. 87. ' Loc. cit., p. 86. 



4n 2 



