1897. SOME NEW BOOKS. 345 



and the sexuality of the ascomycetous fungi is now definitely asserted, 

 chiefly on the basis of Harper's observations. 



The number of figures has grown from 193 to 221 ; the increase, 

 however, is due to new illustrations of apparatus. In the descriptive 

 chapters a certain number of old figures have disappeared, and some 

 fresh ones have taken their place. Some of the omissions, both as 

 regards descriptions and illustrations, will certainly be regretted by a 

 reader who is familiar with the earlier editions. The roots of vascular 

 cryptogams, for example, now come off very badly, with 5^ lines of 

 text, and no figures, (p. 254). In the chapter on algse the excisions 

 are still more lamentable, for Batrachospermum and Fiicits are now left 

 out altogether ; we cannot but regard these omissions as a change for 

 the worse. The best figures illustrating the reproductive processes 

 in the fir have also been sacrificed. On the other hand, we find a few 

 welcome additions to the illustrations, especially among those relating 

 to the anatomy of the Scotch fir and the lime-tree. On the whole, 

 however, we fear that the loss, in the matter of illustrations, out- 

 weighs the gain. 



The ideas of Van Tieghem {see Natural Science, vol. ix., p. 147) 

 have had their due influence on the anatomical part of the book, though 

 the term " stele," is not introduced until the Pteridophyta are reached 

 (p. 247). The homology between the central cylinder of the stem, 

 and that of the root is rightly emphasised, and justice is done to the 

 French anatomist to whom we owe this fertile conception (p. 320). 

 In one point, however, we have noticed that the stelar theory is not 

 consistently applied. On p. 289 the central cylinder in the stem of 

 Hippiiris is still described as a " cauline vascular bundle," whereas it 

 is manifestly not a single bundle at all, but an entire stele. 



Many readers will turn at once to the concluding chapter, in 

 order to learn the author's present views on the questions in dispute 

 as to the nucleus and its division. Their curiosity will be rewarded, 

 for on two of the burning histological questions of the day the author 

 takes up a somewhat unexpected position. As regards the existence 

 of centrosomes in plants he has very decided views, saying, in so 

 many words, that " As the investigations on the botanical side now 

 show, individualised centrosomes are peculiar, in the Vegetable King- 

 dom, to the Thallophyta and Bryophyta ; they are absent from 

 Pteridophyta and Phanerogams" (p. 611). Considering how recently 

 almost all histologists (including the author) accepted Guignard's 

 observations on the lily as affording the classical examples of centro- 

 somes in plants, this strong negative expression of opinion is some^ 

 what surprising. It must be alUowed, however, that the remarkable 

 absence, so far, of confirmatory evidence, goes far to justify it. Prof. 

 J. Bretland Farmer's discoveries of centrosomes in the Hepaticae now 

 occupy a prominent place in this chapter. 



On the question of a reduction-division in the maturation of the 

 sexual cells, Prof. Strasburger, whose openness of mind is proverbial 

 among botanists, completely changes his position. He now asserts 

 positively that in the second nuclear division of the pollen-mother- 

 cells, the chromosomes are divided transversely and not longitudinally, 

 so that here a true reduction-division, in Weismann's sense, takes 

 place. This statement is in direct contradiction to the results of the 

 most recent and careful work on the subject, notably that of Miss E. 

 Sargant, and we cannot but regret the introduction of a dogmatic 

 pronouncement, on so doubtful a point, into a book designed for 

 students. 



If we have found certain features of the book open to criticism, 



