68 The Scottish Naturalist. 



and the special cells (spores) destined for the reproduction of 

 the species are reached. The basidium is first a simple cell, 

 seen in two positions, as at h, h. This simple cell becomes 

 potentially (but often indefinitely) divided by a longitudinal 

 partition, as at j, j ; each of these divided portions produces 

 a branch, as at k, k, and each of these branches bears a spore 

 (l, l), which in its turn is again cut off by cell division, this 

 time transversely. The basidium is now again longitudinally 

 divided at m, m ; these portions in their turn also produce new 

 branches, which give rise to two more spores (o, o), each spore 

 again cut off by a transverse septum. As the two last formed 

 spores increase in size they gradually push the two old ones 

 p, p, off their supports, so that unless the whole process is very 

 carefully watched it might be concluded that the Mushroom 

 produces only two spores (instead of four) on each basidium, as 

 stated by Professor Sachs. 



The mature spores on germination of course reproduce the 

 species by means of a series of new cells. All experiments prove 

 the life of the spore to be very short, but when the spore 

 once germinates and forms spawn the latter material has great 

 tenacity of life, and this mycelium is commonly, if not always, 

 perennial. 



OONTKIBUTIONS TO THE DESMID TLOEA Or PEETHSHIRE/ 



No. I. 

 By JOHN ROY. 



So far as I knoAV, the following fragment is the first attempt which has 

 been made to give an enumeration of the Desmids of this large and impor- 

 tant county. The list here given, tliough not large, contains nearly as 

 many species, as are given by Ralfs, in 1848, for the whole of Britain. Na 

 doubt it will be greatly increased. The present list is the result of the 

 examination of " gatherings " — from Mcthven Bog, Arnbothie, Durdie 

 Moor, Rannoch, and near Tyndrum, sent me by Dr. Buchanan White — from 

 Glcnshee, by Rev. J. P'ergusson — from Birnam Hill, Fowlis Wester, Tay- 

 mount, and near Scone, by Mr. W. Rutherford, — from Atholeand Glenshee 

 collected by myself. The name of the localities will indicate the collectors, 

 of each species. For a note of one species, Cosmariiim cymatojylcurum, 



* Communicated to the Perthshire Society of Natural Science, January^ 

 1877. 



