230 The Plant World. 



and 106; and Herre Proc. Wash. Acad. Sci., on pages 63 and 109. 

 There are occasional incomplete citations, some giving the au- 

 thor only, others omitting the series, volume number, page, 

 or the year of publication. Absolute unifonnity and complete- 

 ness of citation are difficult to obtain, but are helpful to the 

 student and of sufficient importance to warrant great pains. 



The diagnoses are of sufficient clearness and exactness, but 

 often lack certain characters that would have added to their 

 value. Measurements of apothecia are rarely given, though 

 easily made and valuable in determining lichens. Often it is 

 not even stated whether these structures are large,, medium 

 sized, small or minute. Measurements of foliose and fruticose 

 thalli are easily made and are very useful in determinations, but 

 they are not given. These measurements may also often be made 

 for crustose lichens, but not for all, since the thallus here is usually 

 a compound structure and often runs together and covers a large 

 area of the substratum. Measurements of asci are occasionally 

 given, and if worth including, they should be given for all species 

 to be had in fruit. Careful statement is rnore or less frequently 

 iTiade regarding the epithecium, the hymenium, the paraphyses, 

 the asci and' the hypothecium, but more or less of this is o.mitted 

 for certain species or whole genera. A uniform system, of ex-' 

 amining specimens and a resulting likeness in form is a great aid 

 in using the descriptions. The author has used "hymenium" 

 in some descriptions and the synonymous term "thecium" in' 

 others. Uniform use of one or the other of these terms would 

 have been better for the student. As a whole the diagnoses are 

 good and will work well in determining the plants. 



Giving spore measurements in the form of a fraction, making 

 a break in the line, makes reading difficult and is an objection- 

 able feature probably introduced by the publishers. Setting 

 off thallus and apothecial characters in separate paragraphs in 

 the descriptions of species is unusual, but is commendable as one 

 is able to refer to the portion of the description pertaining to 

 either more readily. But the author has departed from this 

 plan in occasional species, and this is sure to puzzle for a moment 

 those who become accustomed to his general plan. The de- 

 scriptions of genera and families are partly run in one paragraph 

 and in part after the plan adopted for the species. It is im- 



