62 



KNOWLEDGE. 



February, 1913. 



Figure 



of the district is occupied by the Moine gneisses, which are 

 paragneisses representing a great sedimentary series originally 

 composed of sandstones, pebbly grits, and sandy shales. The 

 Moine is divided into four groups, of which the one supposed 

 to be the highest in stratigraphical sequence is pelitic or semi- 

 pelitic in composition, and is 

 invaded by a great mass of 

 foliated granite (augen-gneiss), 

 with subordinate basic and 

 alkaline varieties. All the latter 

 were intruded into the Moine 

 sediments prior to the move- 

 ments which transformed the 

 rocks into gneisses. This is 

 shown by the fact that the Carn 

 Chuinneag granite has still 

 preserved around it an aureole 

 of contact - metamorphism 

 which has resulted in the pro- 

 duction of hard, fine-grained 

 hornfels from the original 

 sandy shalesof the Moine. The 

 induration of the hornfels has 



been such that, in many places, they have completely resisted the 

 gneiss-making movements,and are in substantially thesamecon- 

 dition as when first formed. Although completely recrystal- 

 lized these hornfels have never been deformed or sheared, and 

 have preserved a fine sedimentary lamination. Even sun- 

 c racks and ripple-marks have been observed on the surfaces 

 of the bedding planes. They, 

 therefore, prove up to the 

 hilt the original sedimentary 

 character of the great series 

 of Moine gneisses which 

 occupy so much of the 

 North of Scotland. 



MICROSCOPY. 



By F.R.M.S. 



A "DOMESTIC" FUN- 

 GUS. — Owing to the very 

 wet autumn a damp spot 

 appeared on the ceiling of a 

 bedroom, and in a short time 

 a small fungus developed on 

 it. It is a species not in- 

 frequent under similar cir- 

 cumstances, though probably 

 seldom identified. It begins 

 as a cottony web-like my- 

 celium, very delicate and 

 invisible on the white of the 

 ceiling, the threads composing 

 it being without colour. On 

 this arise minute, almost 

 spherical, bodies, the micro- 

 scope showing them to consist 

 of fine filaments arranged side 

 by side. As growth proceeds, 

 these spread at the top, 

 forming somewhat cup shaped 

 objects, but commonly much 

 distorted by pressure as they 

 usually occur close together 

 in patches. Inside they are 

 packed with parapliyses, long 



hair-like objects, and asci (plural of ascus) narrow sacs, each 

 containing at maturity eight oval thin-walled sporidia, arranged 

 in one row ; when ripe they measure from sixteen to eighteen 

 /* long, by about eight ^ wide, and are then ejected by means 

 of any change of temperature or moisture. The little fungi 

 are usually pale salmon pink, but sometimes are white, though 

 apparently differing in no other way. This species is named 

 Peziza domestica, as it is most commonly found on damp 

 ceilings and the plaster of walls in houses, but it occasionally 



Peziza domestica. 



b 



L 



\ 



V 7 



Figure 66. Natal Psychidae (natural size). 



arises also on burnt ground. There are some hundreds of 

 species of the genus Peziza, which are in most cases elegant 

 little cups often very minute, and grow on various objects out 

 of doors, such as twigs, leaves, and other refuse, particularly 

 of a vegetable character. This example is not a very typical 



one, as the body of it is 

 scarcely cup - shaped, but 

 rather sub-cylindrical with a 

 conical base, and shows no 

 hollow. It is small, measuring 

 only about • 5 millimetres in 

 diameter and frequently much 

 less. The Pezizas are members 

 of the Discomycetes, a very 

 large group of the Ascomy- 

 cetes, which are so named 

 because, as in this case, the 

 spores are formed in an 

 ascus. The spores are called 

 sporidia as a distinction 

 from those arising without this 

 organ. In Figure 65, A shows a 

 young and mature specimen 

 seated on the mycelium ; above is sketched a surface view 

 showing the irregular form caused by crowding. At B is a 

 sectional view of the fungus on a larger scale, showing the 

 asci with sporidia in various stages of growth, among the 

 numerous paraphyses ; above is some of the web - like 

 mycelium ; and at c an ascus with sporidia, two paraphyses 



and two free sporidia, all 

 more highly magnified. 



Jas. Burton. 



PSYCHIDAE.— The cat- 

 erpillars of the Psychidae 

 are amongst the most curious 

 and wonderful to be found 

 in the insect world, since they 

 make and live in houses of 

 marvellous construction which 

 they carry about with them 

 wherever they go. These 

 houses differ in shape and 

 material in different species, 

 and though our British ex- 

 amples are small and incon- 

 spicuous, some of those 

 found in South Africa and 

 India reach a length of over 

 three inches. Our illustration 

 gives a selection of typical 

 forms from Natal, drawn 

 natural size. Of these, Figure 

 66a shows a caterpillar with 

 its head and first three seg- 

 ments protruding from its 

 house, the rest of the body 

 remaining inside. In this 

 manner it walks about and 

 feeds, always dragging its 

 house with it, which in this 

 instance is formed externally 

 of small sticks cut into short 

 lengths symmetrically arrang- 

 ed and fastened together 

 with silken threads. The 

 inside is lined with a smooth 

 blanket of silk, quite closed at one end, but having a door at 

 the other end constructed of a number of stiff pieces of dried 

 grass fastened round the edge of the blanket and attached to 

 it in such a manner that when the occupant retires within, it 

 can close them down and cause them to interlace so effectually 

 that not even the smallest of insect enemies could gain admit- 

 tance. When night approaches the caterpillar suspends its 

 house from the branch of a tree by a silken cord, and then, re- 

 treating inside, closes the door and snugly reposes in its blanket 



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1 



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