xviii 



INTRODUCTION. 



colour J substance with substance, form with form (under the title Character of Frond), 

 &c., and a plant referred to the one with which it proves to agree. 



It is true, the absence of scientific generic classification and headings makes it 

 difficult at first to discover to which set of species a plant may belong; but, to meet 

 this difficulty, two attempts are now made; one of which is to throw brief generic 

 and specific distinctions together in the descriptions. Thus, on t?he first page, in 

 the account of the Sargassums, the statement that they have "branches bearing 

 distinct leaves" is made of both, and is followed in both cases by a more particular 

 description of the leaves. Now the fact of "bearing distinct leaves'' is a generic 

 character, and separates the Sargassums from all the other plants that follow; whereas 

 the minute differences as to loidth, the presence of pores in the leaves, &c., are among 

 the specific ones wliich distinguish S. valgare from S. hacciferum. 



So of the Folysiphonias (Plate XXV., &c.), the true generic characters, that they 

 are thread-like, and that the threads are jointed, and that the joints are marked 

 with upright lines (internal tubes seen through), are repeated under each species; 

 while the specific distinctions as to the number of tubes visible, the more or less 

 obscurity of the joints, and other matters, are added to each. 



But, besides this, in the second place, there will be found appended to this volume 

 a Synopsis of Sea-weed Appeay^atices, which it is hoped will be a great assistance to 

 the collector in tracing any plant he may meet with to its generic, and, finally, its 

 specific, home. In this the first step towards algological classification is as clearly 

 marked as in the most scientific works, viz. the division of algse into three chief 

 colour-groups, — olive, red, and grass-green:* but this stage over, scientific classification 

 is laid aside, and the plants are grouped together by the more obvious characters of 

 form and habit of growth. To begin at the beginning, however. The first inquiry 

 of a collector must still be — Is my plant olive, red, or grass-green? And this he 

 nmst find out whenever he wishes to ascertain its name. In most cases it will be 

 easy enough to do so, but in others lie can only accomplish it by holding up the 

 plant to the light, or by examining through a pocket lens (a magnifying-glass used 

 by all botanists, and to be carried in the pocket); or, better still, under the micro- 

 scope. And here he must bear in mind that all algse are coloured one of the three 

 colours named, unless faded by exposure. The tempting white bits so common on 

 the shore near high-water mark, therefore, are worthless, except to make a variety 

 of appearance in a sea-weed picture or basket. 



The colour ascertained, he now knows in which of the three colour-groups to look 

 for his plant, and may proceed next to consider to which of the principal divisions 

 of its group it belongs; whether to the flats, the cylindricals (i.e. those shaped 

 like a thread, whether coarse or slender), the incrustations, or irregular lumps. 

 Then — if flat, for instance — he must go on to observe whether it is with or without 

 a iiddrib; whether leaf-like or irregular in shape; whether hranched or unhranched, 

 &c. ; for it is impossible to do more here than give a general idea of how the inves- 



* Not that the colour-groups are so arranged because of colour, but because of 

 structure; consequently, in a few cases where colour and structure clash, colour gives 

 way. Hence the exceptional red cases in the grass-green group, where the structure 

 is strictly that of grass-green plants (Figs. 345 to 350). 



