THE PLANT WORLD 105 



defensive, while shaking- a branch will cause a good part of the garrison 

 to turn out prepared to fight. 



In the two plants we have been considering, it will be noticed that it is 

 near the young and tender organs that the ant-guard is mostly kept, and 

 these are of course the parts needing most protection. When leaf -cutting 

 ants are absent, the principal enemies to be feared are caterpillars and 

 herbivorous mammalia, and these also much prefer to eat the younger 

 parts. Although the danger from these animals is not so grave as from 

 the leaf -cutters, it is of enough importance to make some means of 

 defense of decided advantage even to plants of our climate. We have no 

 plants that give permanent lodgings to a body-guard, but not a few of 

 our common trees and flowers have on their most vulnerable parts well 

 developed nectar glands which attract considerable numbers of ants, 

 wasps, beetles and other insects that would soon kill a caterpillar or 

 effectually deter any browsing animal from eating much of the plant on 

 which they were. 



Our poplars, for example, have a pair of glands on the first few leaves 

 of a shoot. A sweetish liquid is secreted in abundance from them, and 

 almost any time of the day ants or other insects may be seen at the 

 glands sucking the nectar greedily. Peach-trees have several glands on 

 the edges of the leaf-blade, and cherry-trees have, as a rule, two pairs of 

 glands on the leafstalks. In all of these cases the insect-guard is much 

 more numerous on saplings or on the lower branches of young trees 

 than upon the higher portions of old trees, where there is less need of 

 their presence. Numerous ants are attracted to the flower-buds of the 

 trumpet -creeper by the sweet exudations of glands clustered on the under 

 side where the rain and dew would be least likely to wash away the 

 nectar. The common peony is also provided with nectar-glands on the 

 flower-buds, and many other cultivated plants could be mentioned which 

 offer nectar to attract a body-guard. 



Dr. C. E. Waters, of Johns Hopkins University, well known to fern 

 students in this country through his numerous papers in The Plant 

 World and The Fern Bulletin and for his " Analytical Key," based on 

 cross-sections of fern stems, will shortly publish through Henry Holt 

 and Company a book entitled "Ferns," which is likely to prove the 

 leading popular work on this group. It will contain over 200 illustra- 

 tions, the majority original photographs ; and with respect to this 

 feature it can be confidently asserted that no finer examples of fern 

 photography have ever been produced. Dr. Waters brings to his work 

 fifteen years of experience in field and herbarium study, and the book 

 may be expected to prove of permanent scientific value, as well as to 

 satisfy a want which existing popular treatises have but imperfectly filled. 



