1886.] affecting Abies smitMana, Forhes. 141 



the behaviour of this parasite, as compared with the first species de- 

 scribed, lies in this that not every needle of an attacked shoot is 

 involved. Indeed, only a few needles may be affected, although fre- 

 quently the greater number are (fig. 1). Nevertheless, some inter- 

 mediate needles always remain free. Again, no marked hypertrophy 

 of the tissues is caused by this parasite, and the affected needles 

 are not curved. Each affected needle usually bears several ascidia, the 

 number varying from four to thirteen or even more. A large zone of 

 yellow discoloration surrounds each secidium. If only a few ^cidia are 

 borne, and these at some distance from one another, a corresponding 

 number of yellow rings encircles the needle ; but when the secidia are nu- 

 merous, the whole needle may be uniformly discoloured with the excep- 

 tion of about a quarter of an inch of its extremity. Whilst the peridia 

 are still unopened, the secidia appear usually as long linear yellowish swel- 

 lings with their long axes coincident with the length of the needles ; but 

 they are sometimes short and spherical. They occasionally attain a length 

 of 2*5 m.m., rarely more, and when ripe open by irregular frayed rents 

 on their summits. The peridium is then seen to be white. The aecidia 

 are usually borne on the upper surfaces of the needles, though frequently 

 also on their sides, but never on their lower surfaces. The spermagonia, 

 which may be recognised as minute dark spots, are irregularly scattered 

 all over the needle. 



Microscopical Characters. — In a transverse section of a needle through 

 an eecidium but little derangement of the normal tissue elements will 

 be observed. Thus, the resin canals are not obliterated, and the general 

 arrangement of the palisade-like parenchyma-cells is maintained every- 

 where, except where replaced by the gecidial fructification. The central 

 wood-bundle is not disturbed. The eecidia are buried deeply in the 

 parenchymatous tissue with generally only one layer of these cells be- 

 tween their bases and the endodermal sheath surrounding the central 

 bundle (fig. 7). As the secidial fructification ripens, the hypodermal 

 layer of cells together with the overlying epidermal layer is first 

 lifted and then rent. Ripe eecidia in such transverse sections measure 

 about 0'294 m.m. in breadth and 0*259 m.m. in depth. They are 

 covered by a peridium of a single layer of long flat cells each 

 measuring on an average 36 to 60 fx in length by 20 fx in breadth (figs. 5. 

 and 7) . At the basis of ^cidia and spermagonia mycelial filaments are 

 aggregated in masses, but elsewhere they are sparingly present. At 

 such places the masses of filaments dissociate the parenchyma-cells. The 

 mycelium nowhere penetrates the cells, and, consequently, there are no 

 haustoria. The hyphse vary in diameter from 4 to 5 /a in diameter. 

 They contain a few minute globules of orange-yellow oil (fig. 2). Fila- 



