June 1, 1SG6.] 



v SCIENCE-GOSSIP. 



127 



appear. Either balsam or caslor-oil may be used to 

 mount, but balsam brings the outlines up more 

 sharply than the oil. 



Eor gallic acid I use a nearly saturated solution 

 in cold water, which I prefer to evaporate rather 

 quickly. The crystals are smaller with, the rapid 

 evaporation, but prettier. When the solution is 

 evaporated slowly, the crystals present an acicular 

 form with no very interesting appearance, unless in 

 the course of their formation they' meet with some 

 obstruction or impurity, when they exhibit a form 

 not unlike the "eye" in the peacock's tail-feathers, 

 as pointed out by Mr. Davics in his excellent little 

 handbook, when treating of pyro-gallic acid. On 

 the other hand, by rapid evaporation the crystals 

 assume the shape of small bundles of twigs tied 

 together at one end, and present varied shades of 

 colour with the selenite plate. As to mounting, 

 these crystals seem somewhat capricious. The first 

 slide I prepared was put up in castor-oil, and it 

 stands well now, fourteen months after. Upon 

 using the same medium, however, with subsequent 

 specimens, they immediately faded away and dis- 

 solved in the oil, owing to some cause I cannot 

 explain. Since then I have used balsam, and have 

 not lost a single slide. 



Salicine must be fused upon the slide itself. The 

 only precaution to be observed is not to overheat it. 

 Spread the salt as thinly as possible over the centre 

 of the slide, which must then be held over a lamp in 

 a pair of wooden forceps, as the temperature required 

 is very considerable. By beginning at one end, and 

 gradually moving the slide as the fusion proceeds, 

 all chance of driving out too great a quantity of 

 water from the salt will be avoided. The sort of 

 paste thus formed upon the slide must be gently and 

 evenly spread over the surface with a knife, and 

 upon cooling the crystals will form. The crystals 

 may also be procured from a strong solution of the 

 salt iu water, but they are much smaller, and do not 

 exhibit the same brilliancy of colour as those ob- 

 tained by fusion. 



The mixture of the two sulphates is so fully and 

 carefully described by Mr. Davies in his handbook 

 (pp. 76 and 77) that I must refer those interested to 

 the book itself. I would recommend the piercing of 

 the film, which is there mentioned, as giving 

 certainty to the production of a good slide. The 

 beauty of the resulting crystals fully justifies the 

 encomiums passed upon them by Mr. Davies. 



As an addendum to the above remarks, let me 

 state that much must be learned by actual experi- 

 ence ; for example, if the stirring of the sulphate of 

 copper or iron solutions be carried too far, the 

 crystals will be very small, and much too crowded. 

 If, on the other hand, it be not continued sufficiently 

 long, the slide wdl consist only iu part of perfect 

 rhombic crystals. The time to desist is, when a 

 peculiar gritty feeling is experienced upon the con- 



tact of the glass-rod and the slide : no description 

 of this will convey the exact idea, but it will readily 

 be felt. If examined at this stage under the micro- 

 scope, although nothing can be discerned by the 

 unassisted eye, the crystals will be found forming, 

 and upon the dark ground afforded by the polari- 

 scope exhibit a most beautiful appearance, like 

 jewels upon black velvet. 



Iu conclusion, I beg the consideration of those 

 more experienced than myself. Though other 

 methods may give as good results, my experience 

 proves that good and perfect slides may be obtained 

 by the methods described above. 



E. M. 



INSECT EUNGI. 



f\F all the curious forms which fungi assume, none 

 ^ are more curious or interesting than those 

 which are occasionally developed on insects. These 

 productions have, some of them, been for a longtime 

 known, but, until recently, only bttle understood. 

 As an illustration of the structure and development 

 of these parasites, we will take a species which 

 recently was observed more commonly than usual 

 in a brickfield, near Hitchin, in Hertfordshire. This, 

 which is known to mycologists as Torrubia entomor- 

 rhiza, was attached to the larvse of the swift-moth 

 {Hepialvs hqndinus, fig. IIS) in most instances, only 

 one individual being developed on a single larva, but 

 occasionally two. It consists of a white, branched 

 mycelium, spreading externally over the insect, and 

 internally absorbing the natural structure and con- 

 verting it into a kind of pulverulent sclerotium. 



Fig. 118. Torrubia entomorrhUa, natural size; attached to 

 larvse of a moth. 



Erom near the head of the larva, as we observed 

 generally from the second joint, and at the back of 

 the head arose a stem of from three quarters of an 

 inch to two inches in'length 3 bearing at its summit 



