92 OF THE MARINE ALG.E. 



only whole or perfect specimens ; by which I mean such as 

 are provided with the disk by which they were fixed when 

 in life, or at any rate with as much of it as possible, in 

 order to exhibit the plant's natural habit. Fragments torn 

 off the main stem look very pretty, and do well enough to 

 adorn a lady's album, but, as a rule, are valueless to the 

 botanist. In many cases it is absolutely necessary to have 

 the entire plant before one's eyes to determine with cer- 

 tainty its place in the system of nature. I will bring 

 forward a single example. The genera Callithamnion and 

 Phlebothamnion are separated on the ground of the former 

 being ' corticate '• — that is to say, furnished with a cortical or 

 external integument, which is wanting in the latter. Now, 

 there are instances (as I have myself repeatedly ex- 

 joerienced) where this outer stratum is developed for a 

 short space only above the point of attachment, the whole 

 of the upper portion of the stem being naked. If, then, the 

 student (instead of gathering the whole plant) is contented 

 with specimens taken from above the portion invested with 

 cortex, how is it possible for him to determine to which 

 of the two genera his example belongs, since he has 

 deprived himself of the only characteristic mark by which 

 they are distinguished ? Much the same may be said of 

 the different species of Polysiphonia. 



When, again, the collector comes across Algae flourishing 

 in large tangled groups, he must take care while separating 

 them to secure a sufficiency of material for future obser- 

 vation. It is a sound axiom in domestic economy that 

 frugality applied in the wrong place does but aggravate 

 difficulties. And it is as true here as in the more serious 

 matters of life. Many a chance of determining the true 

 position and natural habit of a plant has been lost from the 

 collector having neglected to gather sufficient material on 

 the spot and at the right time. A single stem of a Cera- 

 mium may perhaps exhibit the generic and specific charac- 

 ters sufficiently well ; but, however beautifully laid out, it 

 can never set before the eye of the observer the great massy 



