April 2^, 1876] 



NA TURE 



to refer to each of the above forms separately, and to 

 illustrate each to an uniform scale. Therefore in the 

 present paper I will confine myself to the description 

 of the two forms of Artotrogus, and leave the considera- 

 tion of Peronospora and Pythium with De Bar>''s criti- 

 cisms of my obser\-ations for another paper. 



I. — Artotrogus, Mont. 



To make my description of Artotrogus quite plain, it 

 is necessary to briefly recapitulate the early history 

 of the potato-fungus. Mdlle. Libert was one of the first 

 to describe this in 1844. In the same year Mr. Berkeley 

 writes he first saw diseased potatoes. 



In 1845 Dr. Montagne described and illustrated the 

 potato fungus. In his illustrations he included certain 

 spherical bodies found in spent potatoes by Dr. Rayer ; 

 these bodies were attached to threads, some of the bodies 

 being termimal (Fig. i, a), and others within the threads 



be made for the sketch of the turnip Artotrogus (Fig. 2), 

 as it was made in 1849 when resting-spores were little 

 understood, but it is clear that Mr. Broome detected 



Fig. I. — Artotrogus hydHOSp<irus,'i>\aTi\. A, B, c. Oogonia from Montagne's 

 original camrra-Iucida diawing. D. Echinulate oogonium from L:c Uary 

 (" Resear hes,'" p. 256, Fig. 3), X 4C0 dia. 



(Fig. I, BC\ just as true oogonia are now known to occur 

 in Cjstopus and other of the Peronospores. A third 

 form (Fig. I, d), was more or less echinulate, and this 

 was assumed to be the matuie spore. Dr. Montagne, in 

 1845, did not thoroughly comprehend the meaning of 

 these bodies, so he named them provisionally Artotrogus. 



From 1S45 till 1875, whtn I rediscovered the entire 

 series of these bodies in direct connection with Perono- 

 spora infestans, in the Chiswick tubers, no record of their 

 rediscovery had ever been published. Botanists had 

 sought for Artotrogus in vain. 



In 1846, in the first vol. of the Journal of the Royal 

 Horticultural Society, the Rev. M. J. Berkeley published 

 his famous paper on the potato-murrain (the essay is 

 dated Nov. 22, 1845), and in this paper Mr. Berkeley 

 reproduces the description and illustration of Montagne's 

 Artotrogus. Mr. Berkele/s published belief has for many 

 years been that the spherical and echinulate forms of 

 Artotrogus belong to no other than the secondary con- 

 dition of the potato fungus. 



In 1849, Mr. C. Edmund Broome, of Batheaston, dis- 

 covered a second species of Artotrogus ; this was found 

 in decayed turnip. A copy of the original camera- 

 lucida drawing made by Montagne is here reproduced. 

 It shows the m) celial threads and the mature resting- 

 spore at E. 



Fourteen years afterwards (1863), Prof. A, De Bary 

 published a paper on the development of parasitic fungi 

 in the Annates des Sciences Naturelles, vol. xx. In this 

 paper the author illustrated, amongst other things, the 

 resting-spore of Peronospora parasitica, Corda, a plant 

 common upon turnips, &c. Part of De Bary's illustra- 

 tion is here reproduced to show the probability of the 

 second described species of Artotrogus being identical 

 with the Peronospora. Some allowance must of course 



Fig. 2.— Artotrogus on decayed Wxrm^ ^=^ Per<mesf<n'a parasitica, Corda- 

 X 400 dia. 



not only the resting-spore with its collapsed oogonium, 

 but probably also a group of antheridia 'see the de- 

 tached antheridium in De Bary's illustration. Fig. 3}. 



This probable identity of the Artotrogus and Perono- 

 spora of the turnip, points in the direction of the probable 

 correctness of Mr. Berkeley's views as to the Artotrogus 

 of the potato. The oogonia of the turnip parasite are 

 similar in size and form with the oogonia found in potatoes, 

 and to these latter I shall now return. 



Fig. 3. — Pcrotiosfiora parasilica, Corda. Resting-spores and detached 

 antheridium (De Bary, "Ann. des Sc Nat.," 4th series, voL xx., PL X., 

 Fig. 5-7), X 400 dia. 



The bodies found by me in the Chiswick tubers I have 

 from the first identified with Montagne's Artotrogus, 

 though De Bary in his criticisms has found it convenient 

 to omit all mention of this fact. But De Bary himself 

 now illustrates the same bodies '" from Montagne's ori- 

 ginal specimen ;" this illustration is here reproduced 

 (Fig. 4), and I can certify as to its general correctness 

 with the reservations (i, that the oogonia shown are 

 larger than any I have seen in the " original specimens ; " 

 (2) larger than any Montagne has figured ; and (3) that De 

 Bary has omitted all the terminal oogonia. In Mon- 

 tagne's original camera lucida drawing there are three 

 terminal oogonia, one is reproduced at A (Fig. i), with 

 two similar bodies intercalated at B c. 



De Bary (as well as Montagne, Berkeley, and myself) 

 has also met with the more or less echinulate bodies, and 

 one of De Bary's illustrations is reproduced, at D (Fig. i). 

 I agree as to its general accuracy. 



Now whilst De Bary contends that all these forms are 

 distinct species of fungi, and not belonging to the potato 

 fungus, I maintain with Berkeley, and other competent 



