6 PREFACE. 



has been because the characters are entirely, or almost en- 

 tirely, microscopical. In drawing up the characters it has 

 been necessary in most cases to presume that the student 

 has for study a complete specimen, and has made out all 

 of its characters which are to be seen with the aid of a 

 simple microscope magnifying twenty or thirty diameters. 

 In a few cases the use of a compound microscope magnify- 

 ing one or two hundred diameters is required, but the 

 manipulations called for are mostly very easy. As with 

 synopses in general, so here, much may often be done 

 when certain characters mentioned are unknown, pro- 

 vided the plant in hand agrees perfectly with the descrip- 

 tion in the great majority of its characters. When such 

 is the case, the genus in question will probably be the one 

 to which the plant belongs. It is believed that the synop- 

 sis here offered may be relied on for accuracy to the ex- 

 tent that any plant agreeing in all particulars with the 

 characters limiting a given genus, belongs to that ge- 

 nus. In the arrangement adopted, convenience has been 

 the chief guide, and this has often led to very artificial 

 groupings. 



It is but fair that students using such a book as this 

 should not expect too much of it. In the first place, the 

 plants dealt with are inherently difficult, and it is beyond 

 the power of a book to make them easy. In the second 

 place, the restrictions imposed on the book by the end in 

 view have necessitated many omissions. Furthermore, it 

 is to be expected that use in the field and laboratory will 

 bring to notice points calling for improvement. If the 

 book assists the student in his early efforts to recognize 

 the genera of Cryptogams, it will accomplish what it is 

 intended for. 



While the genera selected are all to be found in New Eng- 

 land, they are by no means confined to this part of the 



