208 



HARDWICKE'S SC IENCE- GO SSIP. 



of the discharged bladders to be carrying from two 

 to four secondary bladders inside (x) ; these secon- 

 dary bodies were in their turn expelled, and grew 

 and produced mycelium as at y, t, y, whilst a few 

 of the same secondary bladders burst and produced 

 from three to six very small zoospores, generally 

 only three. It is a most singular fact that these 

 secondary bladders and zoospores are exactly the 

 same in size with De Bary's Pythium vexans, and 

 about one-sixth or eighth of the bulk of the resting- 

 spores from which they were discharged. With 

 this exception there has not been the slightest 

 approach in any of my material to organisms which 

 might be referred to Pythium. Mr. Plowright 

 writes: "None of my oospores ever burst and 

 produced Pythium or Pythium-like spores." 



My material has contained a large number of 

 dead mites and aphides and a few nematoid 

 worms ; the oogonia and threads were to be 

 seen in all parts of the dead insects, but not in 

 the worms. 



De Bary, in reviewing my observations, says : — 

 "Even if the often-mentioned warty bodies were 

 hybernating oospores of Phytophthora (Perono- 

 spora), like the similar oospores of P. arenariaa, 

 which resemble them, we should not gain much 

 information bearing upon these questions, since 

 their occurrence is, at the best, extraordinarily rare." 

 This sentence is very erroneous ; for although the 

 bodies were apparently rare when 'I first recorded 

 their discovery, they were not necessarily so in a 

 state of nature ; for on continuing the experiments 

 after my first essay was written, the resting-spores 

 were produceed in myriads, and that, too, within the 

 tissues of a comparatively few leaves. During the 

 present spring I have sent mounted preparations of 

 the mature (or almost mature) resting-spores to 

 many of the foremost cryptogamic botanists of 

 Europe, but not one has denied their possible 

 identity with Peronospora infestans. 



Por more than thirty years our Potato crops have 

 been systematically destroyed by two virulent fungi, 

 viz., Peronospora infestans and Fuslsporlum Solani. 

 These two parasites almost invariably work iu com- 

 pany with each other ; they suddenly appear for a 

 few weeks, destroy our crops, and vanish for ten or 

 twelve months, then reappear and repeat the work 

 of destruction. I claim for my work that it is new, 

 and that it has proved how both these fungi hide 

 and sleep through eleven months of the year. As 

 I have kept the resting-spores of both parasites 

 alive artificially in decayed potato-leaves in water, 

 in moist air, and in expressed diluted juice of horse- 

 dung, it conclusively proves to me that the resting- 

 spores hybernate naturally in the same manner. 

 The seat of danger from both parasites is clearly 

 in dung-heaps, ditch sides, and decaying Potato 

 plants. 

 Any method of destroying the resting-spores of 



these pests, or of warding off or mitigating their 

 attacks, obviously depends in a great measure upon 

 a full knowledge of their life-history. That life- 

 history I have endeavoured to the best of my ability 

 to watch and describe, and I am content to let the 

 observations stand on their own merits. Sensibly 

 conducted and extensive field experiments might 

 probably teach some valuable lessons; but it is 

 difficult, if not impossible, for any single individual, 

 whether farmer or botanist, to institute and carry 

 out such experiments. 



With these notes I am only too glad to bring the 

 whole subject (as far as regards my work upon it) 

 to an end. Any one who feels so disposed, and has 

 the time and patience to go over all the experiments 

 and observations again through another entire year 

 can do so. 



MICROSCOPY. 



Ec-RM- ELEMENTS IN WOODY STRUCTURES. — M. 



Moller has recently described some new form- 

 elements in woody substances. In a cross-section 

 of Avicennia africana, e.g., he finds bright con- 

 centric circular lines, which the microscope shows 

 to consist of regular parallelopipedal stone cells. 

 Spiral thickening he finds in the libriform of Protect 

 ericoides, Hort.; so it is not confined exclusively, as 

 Sanio says, to vascular formation. The same natu- 

 ralist has also described some peculiar arrangement 

 of the parenchymatous elements of Aquillaria 

 Agallocha, Reb. 



Volvox globator, &c. — In answer to the ques- 

 tion in last month's Gossip, whether it is usual for 

 the Volvox globator to disappear in a fortnight 

 from its first appearance, I beg to say that it is 

 not. I have found them in a pond in June, and 

 have been able to procure them from the same pond 

 as late as November 13th : this was in 1871. In 

 the same pond, this year, I again found them in 

 June, and they are very numerous at the present 

 time (August 7th). I believe they serve as food for 

 some of the animalculse. As to the other question, 

 Whether caddis- worms are injurious to Rotifers, 

 &c, I am fully persuaded that they are ; and I 

 always carefully exclude them and the various larvae 

 of gnats and dragon-flies, tadpoles of frogs and toads, 

 &c, from the glasses in which mine are kept for 

 observation ; as Melicerta ringens, Floscularia, &c. 

 Most of the larvae and tadpoles, &c, have a knack 

 of travelling up the stems of plants, and nibbling 

 everything that may be growing on them; so that if 

 they do not eat them, they certainly injure aud 

 destroy them.— James Fidlagar. 



The " Sear " Lami*.— Since the construction of 

 my microscope lamp, illustrations of which appeared 

 in your impression of 1st May last, I have added to 



