THE PLANT AS A HOST 



901 



extent that the very hie of the host is 

 at stake. 



It has for long been reahsed that the 

 relations between the plant and the ant 

 present some remarkable points. The 

 frequency with which these active insects 

 are to be found in flowers cannot fail to 

 have attracted the attention of observers. 

 Now, in a certain way. the worker ants 

 are not in the flower for any good purpose, 

 having come to feast on the pollen and 

 nectar. As these insects do not possess 

 wings, they are not helpful in carrying the 

 pollen from one plant to another, as 

 bees and flies often do. Yet we cannot 

 ignore the fact that in many cases the 

 presence of ants in flowers is tolerated, 

 if indeed it is not actually encouraged. 

 As is well known, ants are peculiarly 

 intolerant of the presence of other insects, 

 and there seems no question that on 

 occasion they will render ill-protected 

 flowers a service in eating up other 

 small marauders which come to plunder. 

 It has been said, although the state- 

 ment lacks confirmation, that ants will 

 sometimes frighten bees away from 

 flowers by the attacks which they make 

 upon them. If this be so, the guests 

 are certainly exceeding their duties in 

 driving away the helpful bees. 



Certain plants arc 

 seen tf) develop nec- 

 taries in other parts 

 than the flowers. In 

 the common Laurel 

 these occur at the 

 bases of the leaves on 

 the under side. The 

 Cherry, as well as other 

 allied species, produces 

 nectaries in the form 

 of small glandular 

 swellings on the leaf- 

 stalks. In addition, it 

 is found that the 

 Broad Bean bears nec- 

 taries on its stipules. 

 The actual purpose 

 served by these pro- 

 cesses has long been 

 the subject ol a great 

 deal of speculation. 

 Some have held that 

 they must be regarded 

 as curious protective 



YELLOW KATTLK, 



devices. It is argued that creeping 

 insects bent on plundering the store of 

 good things to be found in the flower 

 are turned aside from their nefarious 

 purpose when they discover the glands 

 secreting nectar. Here is a supply of 

 honey easily secured, so why should the 

 little creatures trouble to go on to the 

 blossom at all ? In the case of the Scab- 

 rous Balsam. Kerner has observed that 

 the drops of honey prfn-ided at the base 

 of every leaf undoubtedly prevent a 

 large number of wingless creatures from 

 getting to the pollen. But it seems that 

 the matter ma}^ be pushed to a still more 

 interesting conclusion. These extra-floral 

 nectaries will, of course, attract large 

 numbers of ants, and the vigorous little 

 creatures will certainly not allow any 

 other visitors. Thus the numbers of 

 sm.all beetles and other insects which 

 happen to be trespassing on the plant 

 are dealt with very effectually. 



The relations of plants and ants are 

 known to be more definitely intimate 

 than in any of the foregoing instances. 

 As long ago as 1688 the old naturaUst 

 John Ray observed the frequent occur- 

 rence of ants in the hollow stems of 

 Cecropia palmata and some other South 

 American plants. It was not until the 

 latter part of last cen- 

 tury that an under- 

 standing of the matter 

 was in any way com- 

 plete. The actual ob- 

 servations were made 

 in the case of the Bull's 

 Horn Acacia. In this 

 tree it was found that 

 the hollow thorns were 

 inhabited by ants, the 

 insects making a hole 

 for their entrance and 

 exit near one of the 

 thorns. In these httle 

 homes they rear their 

 young, and Belt (in 

 Nicaragua) declared 

 that in the wet season 

 every one of the thorns 

 in the trees he ex- 

 amined was inhabited. 

 11 any browsing animal 

 shtmid attack the tree, 

 the ants resent the in- 



A PLANT WHICH 

 IS PARTLY PARASITIC ON GRASS 

 ROOTS. 



