53 



Th. Pergfande expresses the belief that different species 

 of thrips, which were found in many kinds of flowers, may 

 effect cross-pollination. Osborn informs me that two 

 kinds of thrips are common in clover blossoms. Thrips 

 tritici and Phloethrips nigra, but these certainly cannot ffen- 

 erally effect cross-pollination. 



Can the honey bee effect cross-fertilization in Mammoth 

 clover (TrifoUum medium)? It probably can do so as it does 

 in common red clover. I have not studied the flowers of 

 mamoth clover carefully, but so far as I can see, the flowers 

 of the forms in the college collection are about the same size 

 as those of red clover. One form has much smaller heads 

 and the flowers are somewhat smaller, but I am inclined to 

 think that mammoth clover is pollinated principally by bumble 

 bees. The work of honey bees in pollinating white aTid alsike 

 clover is well known, in fact, they can easily accomplish this. 

 One other thought suggests itself to me in this connection. 

 I believe that it is generally supposed that the second crop 

 of clover produces more seed than the first. This, I think, 

 is due to insects, there being a much larger crop of bumble 

 bees at the time of. the second bloom than during the first 

 bloom. 



White Clover. The flowers of TrifoUum rcpens, L., 

 are massed together in the form of a head and 

 hence are quite conspicuous. The odor also helps to attract. 

 The standard has a groove which leads to the nectary. The 

 nectar is secreted at the bottom of the tube formed by the 

 union of the filaments and can only be reached by tlie open" 

 ings, one on each side of the free tenth stamen. An insect, 

 in order to reach the nectar, puts its proboscis underneath 

 the standard. It uses the wings and keel as a resting place, 

 pressing down the latter and causing the stamens and pistil 



