August 25, 1898] 



NATURE 



401 



Semi axis major ... = 102 astronomical units. 

 Combined mass ... = 65 sun's mass. 

 Parallax ... ... = o"-oi97. 



Velocity of system 'm\ _( - 5"i8 g.m. (23-88 Eng. miles) 

 line of sight .../~\ per sec. 



The investigation is one of such delicacy that considerable 

 uncertainty remains as to the data deduced ; but the individual 

 results appear to be sufficiently consistent to warrant the publi- 

 cation of the foregoing provisional values. The results are 

 especially interesting as being the first practical outcome of a 

 suggestion first made by Fox-Talbot in 1871, and developed 

 mathematically by Dr. Rambaut and Dr. See (Nature, vol. 

 liii. p. IS). 



A Catalogue of Fourth-Type Stars. — The Rev, T. E. 

 Espin has recently revised his valuable catalogue of stars of the 

 fourth type (Group VI.) which are at present known, including 

 stars discovered at Harvard and Arequipa, and not before pub- 

 lished {Monthly Notices, vol. Iviii. p. 443). The following 

 summary shows the distribution of the stars in magnitude and 

 in the two hemispheres, the magnitudes of variable stars being 

 entered according to their maxima : — 



Total 



155 



82 



237 



It is considered probable that our knowledge of the number 

 of stars of this type is complete for the northern heavens as 

 far as 89, and for the southern heavens as far as 8*5. The 

 catalogue contains twenty-eight variables to which letters have 

 been assigned, twenty-two being north and six south. " It 

 would appear that almost all the stars of Type IV. are subject 

 to fluctuations in brightness, though the red colour makes it 

 not easy to decide when the variation is small."' 



A YORKSHIRE MOOR.^ 

 II. 

 T^HE Bilberry (or Blueberry, as we ought to call it) is one of 

 ■*■ the few exceptions to the rule that moorland plants are 

 evergreen ; it casts its leaves in early winter. But the younger 

 .stems are green, and take upon themselves the function of 

 leaves, when these are absent. Kerner has described one 

 adaptation of the Bilberry to seasons when water is scarce. 

 .Many plants, especially those of hot and wet climates, throw off 

 the rain-water from their tips, and so keep the roots compar- 

 atively dry ; others direct the water down the branches and stem 

 to the roots. Bilberry is one of the latter sort. The rounded 

 leaves slope downwards towards the leaf-stalk, and from the 

 base of every leaf-stalk starts a pair of grooves, which are sunk 

 in the surface of the stem. A light summer shower is 

 economised by the guiding of the drops towards the roots. 

 Bilberry abounds on the loose and sandy tracts of the moor, 

 and especially on its verges ; it is seldom found upon a deep bed 

 of peat. 



There is a moorland plant which may be said to mimic the 

 heaths, as a Euphorbia mimics a Cactus, or Sarracenia a 

 Nepenthes. Similarity of habit has brought about similarity of 

 .structure. The plant I mean is the Crowberry, which is so like 

 a true heath in its foliage and manner of growth, that even the 

 botanists, who did not fail to remark that the flowers are 

 altogether different, long tried to bring the Crowberry and the 

 heaths as near together in their systems as they could. Crow- 

 berry has the long, dry, wiry stems, the small, narrow, rolled, 

 clustered, evergreen leaves of a true heath. The leaf-margins 

 are turned back till they almost meet, and the narrow cleft be- 

 tween them is obstructed by close-set hairs, so that the trans- 

 piring surface is effectually sheltered. Crowberry is a peat-loving 

 shrub, and is often found with ling and other heaths in the heart 

 of the moor. The berries are a favourite food of birds, which 

 help to disseminate the species. Crowberry has an uncommonly 



1 A discourse given at the Royal Institution, February 1898. By Prof. 

 L. C. Miall, F.R.S. Continued from p. 380. 



NO. 1504, VOL. 58] 



wide distribution, not only in the Arctic and Alpine regions of 

 the Old World, but also in the New. It abounds m Green- 

 land, where the Eskimo use the berries as food, and extract a 

 spirit from them. A very similar species, with red berries, 

 occurs in the Andes. 



The heaths. Bilberry, Crowberry, and many other peat-loving 

 shrubs or trees, have a peculiar root-structure. The usual root- 

 hairs are wanting, and in their place we find a peculiar fungus- 

 growth, which invades the living tissues of the root, sometimes 

 penetrating the cells. There is often a dense mycelial mantle 

 of interwoven filaments, which covers all the finer roots. This 

 looks like parasitism, but the fungus is apparently not a mere 

 para.site, for the tree or shrub shows no sign of injury, but thrives 

 all the better when the fungus is plentiful, and may refuse to 

 grow at all if the fungus is removed. Rhododendron, Ling, 

 most heaths. Bilberry, Crowberry, Broom, Spurge-laurel, Beech 

 and Birch are among the plants which have a mycelial mantle. 



Fig. 7.— Crowberry {Etiipetrum nigrum). A staminate branch, slightly 

 enlarged ; a, part of a pistillate branch ; b, one staminate flower ; c, one 

 pistillate flower. 



If the native soil which clings to the roots of any of these is 

 completely removed, if the fine roots with the mycelial mantle 

 are torn off by careless transplanting, or if peaty matter is with- 

 held, the plant dies, or struggles on with great difficulty until the 

 mycelial mantle is renewed. Such plants cannot, as a rule, be 

 propagated by cuttings, unless special precautions are taken. 

 Frank maintains that the mycelial mantle is the chief means of 

 absorption from the peaty soil, and that the tree or shrub has 

 come to depend upon it. The known facts render this inter- 

 pretation probable, but thorough investigation is still required. 

 In some cases at least the plant can be gradually inured to the 

 absence of a inycelial mantle. I have repeatedly planted crow- 

 berry in a soil devoid of peat. It generally succumbs, but when 

 it survives the first year, it maintains itself and slowly spreads. 

 Microscopic examination shows that the roots of crowberry 

 grown without peat contain no mycelial filaments or very few. 



