408 REVIEW. 



structure of the plants are exactly similar, Avliile the fruc- 

 tification is entirely tlifFerent. As instances he cites some 

 forms of Callithamnion and of Wrangelia, of which it is 

 impossible to determine the genus without microscopic ex- 

 amination of the fruit — and the fruit, alas ! is too often absent 

 in specimens submitted for examination. Hence Professor 

 Agardh draws the conclusion that none of the Floridese can 

 be considered to be correctly placed in the system, whose 

 internal structure and fruit are not known to us by numerous 

 examples ; nor can any dependence be placed upon descrip- 

 tions or figures of sterile forms or analyses of fruit and 

 structure (often either erroneous or defective), of which only 

 a few examples are known. Acting on this principle, he tells 

 us that in this volume, as in the preceding, he has inserted 

 no species in the text which he has not himself examined. 

 Species which he has not seen are either inserted in notes 

 or placed at the end of each genus as " species enquirendse." 

 A few species, easily understood, have been, however, admitted 

 on the faith of well-executed figures. 



" If," says Professor Agardh, ''resting on the fact before us 

 (the imitation or repetition of forms), we go on to conclusions, 

 is it not obvious that the reports we have heard about the 

 arrival of our Algse on distant shores are by no means to be 

 believed, unless the species of difierent localities have been 

 subjected to accurate examination, which, although algolo- 

 gists had the Algae before them, they have generally omitted 

 to make? When we have had an opportunity of comparing 

 specimens from different places, we have shown that these 

 reports are false. With regard to algologists, as to early 

 travellers who have made similar assertions about the higher 

 plants, it has been their error that they regarded nature, not 

 only as not copious, but as poor and scanty." 



In the 'Phycologia Australasica' sixty species are enume- 

 rated as common to the Australian colonies and to this country. 

 On looking through the work before us it wdll be seen how 

 very few of these are found to be exactly identical; many 

 are well-marked varieties, and not a few are essentially 

 different in generic characters. The same remark applies to 

 Alsrse from other countries said to be identical with some of 

 those found on our coasts. 



Professor Agardh, than whom, from his long and wide ex- 

 perience, no one is more competent to form an opinion on 

 the subject, next takes occasion to express his belief in the 

 immutability of species. 



With regard to the determination of the genera of the 

 Florideje the professor states that the characters of most 



