344 REVIEWS— INTRODUCTION TO CRYPTOGAMIC BOTANY. 



probably most readers will tbink bim successful. Tbe second cbapter 

 more fully discusses tbe cbaracters by wbicb cryptogams are dis- 

 tinguisbed, specially examiuing difficult cases ; enlarges on the im- 

 portance and interest of tbe study, lays down some cautions as to 

 tbe mode of pursuing it, illustrates tbe true meaning of analogy, 

 homology, and affinity, attempts to sbow tbat tbere is no near 

 approach to cryptogams in tbe higher divisions of tbe vegetable 

 kingdom ; and, after setting aside tbe notion of spontaneous or 

 equivocal generation as equally untenable in respect to the lower 

 and tbe higher organisms, concludes by dividing all cryptogams into 

 two great sections, regarded by Lindley as classes of the vegetable 

 kingdom — Tballogens and Acrogens. "We quote the summary of 

 characters in tbe first paragraph : " Cellular or more rarely cellular- 

 vascular, flowerless plants, often destitute of stem and foliage, pro- 

 pagated by simple or compound microscopic spores, germinating by 

 means of one or more simple threads, and rarely containing any 

 embryo, sometimes producing a protballus, which gives rise to 

 secondary spores or young embryonic plants, increasing mostly by 

 additions to tbe external surface, exhibiting sexual distinctions, 

 diclinous or monoclinous, but never producing true stamens or pistil, 

 and consequently possessing no true pollen, but, ou tbe contrary, 

 impregnated by spermatozoids, either provided with or destitute of 

 slender flagelliform motile appendages," to which we add the conclu- 

 ding paragraph, containing the distinctive cbaracters of Thallogens 

 and Acrogens : " Tballogens — seldom herbaceous or provided with 

 foliaceous appendages ; foliaceous appendages, if present destitute of 

 stomata. Spores rarely producing a protballus ; and, if so, giving 

 rise to a second order of spores germinating at definite points. 

 Spermatozoids not spiral. Acrogens — mostly herbaceous, and pro- 

 vided with distinct, often stomatiferous foliaceous appendages. 

 Spores, for the most part, producing a protballus, or, if not, compli- 

 cated fruit by means of tbe impregnation of an embryonic cell. 

 Spermatozoids spiral." 



We think it possible tbat our author may be disposed to go to an 

 extreme in his rejection of all affinity between cryptogams and any 

 of tbe higher forms of vegetation. He seems to us quite right in 

 insisting on tbe reality of the distinctions between them, but tbe 

 different groups must approach more nearly at some points than at 

 others, and tbe resemblances which bring certain families into relation 

 are as real though not perhaps as important as their differences. 



