526 



NA TURE 



[April 2J, 1876 



observers, that they are one, including Peronospora. I 

 have seen them all growing from the same threads, and I 

 will now review the grounds on which De Bary refers 

 them to different fungi. 



First, from De Bary's own words, I will show how 

 extremely near the connection was, even with him. The 

 italics are mine. He says (" Researches," p. 256), '• In 

 the tissues of potatoes penetrated with the mycelium of 

 Phytophthora (De Bary's new name for the potato 

 fungus) there sometimes appear other bodies which 

 might be regarded as oogonia or oospores of the potato 

 fungus. I have several limes found them with Pythium 

 vexans in old collapsed tubers which had sprouted in the 

 ground, and once without Pythium in a living stalk which 



Fifi. 4. — Ariotrogiis hydnosporus, Mont. De Bavy's illustration (" Re- 

 searches," p. 258, Fig. 8">, X 4C0 dia. 



had been on the ground. But they were always restricted 

 to those regions which were occupied by the Phytophthora 

 mycelium^ And again, " It was certainly remarkable that 

 they were often situated close to the inner surface of the 

 cell-walls in places where externally the mycelium of 

 Phytophthora undoubtedly ran in the intercellular spaces, 

 or even where a short branch of it penetrated the interior 

 of the cell:' 



In his desire, however, to dissociate these bodies 

 from Peronospora, De Bary (p. 257) first says they were 

 found by Montagne in a " sprouted but not diseased 

 potato." But this statement becomes of no value when 

 De Bary himself confesses (as he does) that with him the 

 oogonia were always restricted to those regions which 

 " were occupied " hy i\\Q Peronospora niyceliu?n. I, too, 

 have found them in similar " regions" and upon the Avv- 



FlG. 5. — OfgoLia oi rc>vitos/o7a iiifesians, Mont. A, B, c. Diflerent forms 

 fiom Chiswick potatoes. D. From De Bary's slide, No. IX. (common 

 in Montagne's preparations). E. From De Bary's slide. No. XI. F. 

 From De Bary's slide, No. X , as sent to the Royal Agricultural 

 Society. 



nospora mycehum. De Bary says (p. 256), " In most 

 cases I found these bodies complete, mature, and without 

 any distinct indication of their being attached to my- 

 celium," and he says the same of Montagne's material 

 and afterwards of mine. But this statement (like the 

 former one) becomes of no value when we find the author 

 writing on the very next page that after " long searching 

 in vain he found them to grow on the extremities of the 

 branches of a mycelium which is very like that of Pythium 

 vexans." And now what is the mycelium in P. vexans 

 like ? De Baiy tells us, on page 253, that it is " scarcely 



possible to driw a positive distinction " between it and 

 the mycelium of Peronospora infestans .' The con- 

 clusion is obvious. 



It is, perhaps, diflficult to explain why a smooth oospore 

 should become a rough or echinulate one, but the fact 

 remains that the phenomenon is perfectly well known in 

 fungi, notably in the spores of some of the Gasteromycetes. 

 Plain and echinulate oospores are also produced on the 

 same plant in some Saprolegnieas. Max Cornu also 

 maintains that Saprolegtiia asterophora of De Bary i.s 

 the same as the warted form of Achlya racemosa of 

 Hildebrand. Dictyuchus also occurs with warted oogons. 

 The three upper figures on the accompanying illustration 

 (Fig. 5) are exact reproductions from different forms of 

 oogonia found by me growing on the same threads with 

 Peronospora infestans. The lower three are from Dc 

 Bary's own specimens sent to the Royal Agricultural 

 Society ; D is from slide ix. (this is also very common on 

 Montagne's preparations) ; E is from De Bary's slide xi., 

 and F is from slide x. A glance at the actual preparations 

 will show that every intermediate form is to be found. 



But De Bary will not see the association, and in his 

 concluding paragraph on Artotrogus (p. 258), he criticises 

 Montagne and Berkeley, and says these authors " have 

 explained the globular cells of both kinds as exhibiting 

 progressive steps in their development, the smooth ones 

 being the younger. For this no reason is ^iven" says De 

 Bary, " nor have I found any in the renewed examination 

 of the specimens. Anyone can scarcely conceive, from 

 the known phenomena of development how the smooth 



Fig. 6. — Restisg-spores of Perotiosfora Holostei, Casparry. x 400 dia. 

 From De Bary's preparation sent to the Royal Agricultural Society. 



thick walled cells (the cell-walls are exactly the same in 

 both) could become the smaller star-shaped ones." 



Now, the accompanying illustrations (especially Fig. i) 

 show De Bary to be quite wrong. The three upper 

 oogonia on Fig. i are from Montagne's own camera- 

 lucida tracing, the left-hand figure. A, is the largest 

 oogonium he has shown, and the right hand oogonium, E, 

 is the smallest. I can testify as to their correctness from 

 an examination of the original material. The starry figure 

 at D is one of the (presumedly) mature bodies, and is 

 reproduced from De Ba7-}''s own figure (" Researches," 

 p. 256, Fig. 3). I reproduce this figure because De Bary calls 

 it the " common form." Now, instead of being smaller, a 

 glance will show this echinulate body to be larger than the 

 largest plain oogotiium found by Montagne. On turning 

 now to Fig. 5 it will be seen there is no " getting smaller" 

 in the case, for all the bodies are as a rule very uniform 

 in size, and if they vary at all they get somewhat larger 

 instead of smaller at maturity. This is the rule, but all 

 botanists know well that the oogonia of the Peronosporea; 

 are liable to vary. A good illustration of this is aff"orded 

 by De Bary's own preparation of P. Holostei, as furnished 

 by him to the Royal Agricultural Society. The accom- 

 panying illustration (Fig. 6) is a camera-lucida reproduction 

 of two oogonia belonging to this species from his own 

 slide, and it shows well how oogonia may vary in size. 



Thus De Bary's notes and criticisms (taken in connec- 

 tion with the observations of other competent observers) 

 on this, the fiist point (Artotrogus), completely fall to 

 the ground. De Bary confesses to having found both 

 forms of Artotrogus in those restricted regions only of 

 diseased potatoes where Peronospora mycelium was un- 

 doubtedly and always present. He moreover found the 

 bodies attached to a mycehum so hke that of Peronospora 



