COLLINS. — THE ALGAE OF JAMAICA. 235 



indicates the affinities of the floras. The tables are useful merely as 

 showing general tendencies, not exact relations. Exactness would be 

 possible only when the districts compared had been explored and studied 

 to the same extent, with the same care and under the same conditions, 

 a thing practically impossible. 



Table No. I. shows the distribution, in the districts named, of each 

 species found in Jamaica ; Table No. II. summarizes by classes the total 

 number of species for each of the seven regions, — it represents less the 

 probable richness of each region, than the extent to which it has been 

 explored. A tolerable test of thoroughness of exploration is often found 

 in the proportion which the Schizophyceae bear to the whole number. 

 Being insignificant, usually microscopic plants, they are quite overlooked 

 by the non-scientific collector. Where the knowledge of a region de- 

 pends on collections made by a non-scientific collector, or by a collector 

 who, however competent in other departments, is not specially an algolo- 

 gist, the red algae constitute a larger, the blue-green a smaller proportion 

 of the whole. 



Tbe Puerto Rico collection, and in great y>art the Canary collection, 

 were made by non-algologists ; the Morocco was made by a skilled al- 

 gologist, but before much was known of the lower algae, or microscopes 

 perfected so that they could be suitably studied. The Biscay collection 

 was the work of one man, a trained algologist, studying the plants on the 

 spot; while the lists for New England and Great Britain cover the most 

 thoroughly studied parts of the world, and the work of generations of 

 botanists. The proportion of Schizophyceae, as shown by Table No. III., 

 follows these conditions fairly well. In the New England list it is ex- 

 ceptionally large, as that list included a number of species, normally 

 fresh water, which were found growing with marine forms, but which 

 usually would not be included in a marine flora. The totals in all parts 

 of the Great Britain list are increased by the fact that in that list the 

 naming of forms is carried out more fully than in any of the others ; the 

 percentage, however, is but little affected by this. 



It is noticeable that in the first five floras, which might be grouped as 

 warm water floras, the red algae constitute over half the whole list, while 

 in the two northern they are less than half, New England, the most 

 arctic in character though not in latitude, having only 37 per cent. 

 Puerto Rico and Jamaica, the most southern, have the highest percentage 

 of green algae, 27 and 28, respectively, they being in the region of the 

 Siphonaceous plants. The Canaries have less of this element, but 

 more than the region farther north. The low percentage of green algae 



