THE DIATOMS OF CANADA 115 



XII 

 The Diatoms of Canada. 



BY 



L. W. Bailey, LL.D., F.K.S.C, and A. H. Mackay, LL.D., F.R.S.C. 



At the preeent time nothing like a synopsis of the diatoms of Canada has been 

 prepared. Indeed with the exception of a few short lists, and the more elaborate 

 papers published by the authors of this article on the diatoms of the Atlantic and 

 Pacific seaboards — the Maritime Provinces in the one insta-nce and Vancotiver island 

 in the otliei* — hardly a single note bearing upon the subject is anywhere to be found. 

 True, in the " Diatoms of North America," as published by Wolle, are contained a 

 large number of forms to be met with in Canada, but there are no descriptions nor 

 a-nything to indicate whether the species figured occur in the latter or only at points 

 much farther south. To make the proposed synopsis satisfactory, it is obviously 

 desirable that it should cover the whole Dominion, and contain records of gatherings 

 from as many different parts of the latter as is possible. It is the object of this paper 

 to contribute to the result referred to by giving lists of species obtained from several 

 widely separated and comparatively inaccessible localities, viz: the Magdalen islands 

 in the gulf of St. Lawrence. St. Mar;\'s Bay, N.S., Montreal, P.Q., the region about 

 Cobalt, 0-At., Parry Sound, Georgian bay and lake Winnipeg. 



DIMENSIONAL FORMULAE USED FOR DL\TOMS. 



The dimensions of each specimen measured are noted in a brief formula to save 

 space and time, and show at a glance the general shape of the individual and the 

 coarseness or fineness of ite sculpture. 



The figures represent microns (the thousandth part of a millimeter). The first 

 number is its length. The numbers within the parenthesis following are breadths 

 which are measured at the centre or in more places if the breadth varies at distinct 

 flexures. When measuring breadths it is important to note whether it is the valval 

 or zonal aspect of the specimen that is in view. Hence V or Z is placed immediately in 

 front of the formula to indicate the side. The figure following " s " after the paren- 

 thesis indicates the •number of lines, dots, etc., in the sculpture within the space of 

 ten microns, thus : V80 (20 :15 :20) s7 means that the Navicula, for instance, is seen 

 from the valval side, is 80 microns long, is bilobed, 20 microns broad with a contrac- 

 tion to 15 microns at the centre. And the sculpture, lines or striae, seven in 10 

 microns. 



In the case of a ba-nd of FragiUana forming a ribbon, say of 3 valves side by side 

 aggregating 15 microns, each 20 microns long, we can take the breadth of the three 

 divided by 3 to get the average, thus : — 



V20(15/3)sl7=V20(5)sl7. 



The first form is fuller — 15 divided by 3 being equal to 5; but it shows the number 

 of valves attached, the breadth of some being possibly greater or less than the 

 average. 



The formula is an adaptation to the ordinary type found in the printing office, 

 and is used here seldom beyond conveying an exact idea of the length and breadth, 

 and fineness of sculpture. When there are two orders of sculpture prominent, the two 



79'55(>— Si 



