189 



later by Bohlin, Blackman and Tansley, West, and Oltmanns, 

 has been accepted as a group coordinate with the Chloro- 

 phyceae, though the author has followed Luther, and Oltmanns, 

 in keeping the Vaucheriaceae in the Chlorophyceae rather than 

 BohUn, and Blackman and Tansley, in transferring them to the 

 Heterokontae. The Flagellates are excluded and the Conjugatae 

 find themselves again under the Chlorophyceae, as with West. 



Keys to the families, genera, and species add much to the 

 working value of the book, as do, also, the one hundred and sixty 

 good figures illustrating most of the principal genera. References 

 to the more important literature and to exsiccatae assist the 

 reader to further information as to points of special or critical 

 interest. 



A carping critic might find now and then in Mr. Collins' work 

 a few features to mention unfavorably, but that would doubtless 

 be more or less true of every book of the sort that was ever pub- 

 lished or that ever will be published. Some of the keys to the 

 species, notably that to the species Penicillus, omit the more 

 distinctive and diagnostic specific characters or translocate them 

 in such a way that the student would be often misled in an 

 attempt to determine species by their aid. Rhipocephalus oh~ 

 longus (Decaisne) Kiitzing, known only from the Bahamas, is 

 omitted altogether. This is evidently a distinct species, often 

 much resembling Penicillus capitatus in habit and much weaken- 

 ing the generic distinction of Rhipocephalus from Penicillus. And 

 there are in the work slips and inaccuracies of a less important 

 character, such as the accidental attributing of figure 148 (Acicu- 

 laria Schenckii) to Borgesen rather than to the present reviewer. 

 But occasional omissions and lapses are of course inevitable in a 

 work of the size and scope of the present one. In bringing to- 

 gether in a single volume and in the English language the de- 

 scriptions of the green algae of North America, Mr. Collins has 

 done much to stimulate and facilitate the study of this interesting 

 group of plants and American students of the algae will not be 

 slow in acknowledging their great indebtedness to him. 



Marshall A. Howe 



