64 FUNGI INJURIOUS TO FIRS. 



C^onta Abietis jn>ctiuatti' is a form reminding us, by its habit and 

 behaviour, of Calyptospora Gccppertiana. 



The Spruces (Picea) are also apt to suffer much from Uredinese, of 

 which the genus Chrysomyxa is one of the most important. Several 

 species of this fungus do considerable damage to the leaves, by causing 

 them to fall prematurely e.y., C. Abietis* C. Rliododendd and C. Ledi 

 the former being autoecious, and only occurring in the Teleuto-spoiv 

 stage, so far as is known ; the two latter being heteroscious, the /Ecidia 

 developing on the leaves of the Spruce, and the Uredo-forms on the 

 leaves of Rhododendron ferrugineuin and R. hirsuturn, and on those of 

 Leduni palusfrre. Farlow says that C. Alietis occurs on Tsur/a 

 canadensis which suggests the probability that this form again is 

 more widely spread than has been supposed hitherto. Miinter states 

 that Picea alba is not affected by this disease. I quote from 

 Sorauer,f and cannot speak from my own knowledge ; but Farlow does 

 not give this fungus on P. alba. 



Spruces (and to a less extent Silver Firs and Pines) are often affected 

 with a disease caused by an Ascomycete (Nectria Cucurbitula ), the 

 hyphse of which find their way through small wounds in the cortex, into 

 the sieve-tubes, etc., of the phloem, and set up a struggle for existence, 

 which is very interesting to the biologist, though it may be viewed with 

 different feelings by the horticulturist. It appears that so long as the 

 Fir is doing well, the parasite is confined to the resting parts of the 

 phloem, and cannot make its way into the active cambial region, the 

 living cells of which go on dividing and growing quite normally ; if 

 the attacked branch is particularly vigorous, the formation of a layer 

 of cork may be accomplished, which cuts off all the diseased tissues, 

 which then dry up and are thrown off. 



It is a particularly instructive fact, however, that if the season is one 

 unfavourable to the rapid and vigorous development of the cambium, or 

 the tree generally, or if conditions exist in the soil or atmosphere 

 which retard the vegetative activity of the cells, the mycelium of 

 the Nectria is enabled to conquer the tissues of the cortex, and even 

 to kill the cambium and penetrate into the young wood. If this 

 happens all the parts above the attacked place are apt to dry up 

 and die, evidently from the stoppage of the water currents up the 

 stem ; this very often occurs with thin watery twigs so-called 

 " unripened wood " such as may be found in shaded situations, or 

 in very damp summers. 



From the dead cortex come the white conidial cushions, about as 

 large as pin-heads, followed by the scarlet stromata with immersed 

 ascogenous fructifications. 



There are many other very interesting points about this disease ; and 

 as it is a type of an exceedingly important series of diseases very 

 little understood in England, attention should be directed to some 

 of the results. 



While relying for the most part on the researches of Hartigj so far 

 as this particular species is concerned, it is only right to say that the 

 following conclusions are based on some experience of my own. 



* Beautiful figures of this are to be found in AVillkonmi, " Die mikroskopisehen Feinde 

 des Waldes," 1867, Taf. IX. The text is now chiefly of historical interest, 

 f "Pflanzenkrankheiten," 2nd edit. 1886, Vol. II. p. 248. 

 " Untersuchungen aus dem Forstlichen-Botanischen Institiit zu Mimchen," I. p. 88. 



