4 BULLETIN 1153, U. S. DEPARTMENT OF AGRICULTURE. 



Reduced sterile involucres are to be reckoned, of course, as a form, 

 of abortion, but of a nature entirely distinct from the direct in- 

 juries that the weevils inflict by puncturing the flower buds to lay 

 their eggs or to feed upon the pollen. The abnormal involucres, hav- 

 ing no flower buds to be attacked by weevils or blasted by unfavorable 

 conditions, are immune from shedding and remain on the plants 

 to the end of the season. The shedding of normal buds after blast- 

 ing involves a loss of the inclosing involucre as well as the support- 

 ing pedicel or stem of the bud, leaving only a rounded scar on the 

 fruiting branch. 



Some of the solitary bracts, representing reduced involucres, are 

 not of the usual expanded form, but narrowly tubular or trumpet 

 shaped. (PI. Ill, Fig. 2.) To form these tubular bracts the margins 

 must have been united or fused together at a very early stage of 

 development, while the abortion of the other bracts and of the 

 flower bud must have taken place at a still earlier stage in the for- 

 mation of the involucre. The tubular bracts may be described as 

 " ascidia," a name that has been applied to similar malformations 

 of leaves in several other families of plants. The marginal teeth 

 of the solitary bracts are reduced in number, especially those of the 

 tubular bracts, or ascidia. Having lost their floral buds at the early 

 stage of development, the reduced involucres can serve only as 

 leaves, and they persist for the remainder of the season, as already 

 stated. The stalks or pedicels of the reduced involucres are very 

 short and slender, more like petioles of small leaves than like pedi- 

 cels of normal buds or bolls. 



Another peculiar feature of these reduced, budless (or ablastic) 

 involucres is their general failure to develop a nectary or honey- 

 secreting pit. which is located at the base of a normal bract. Sup- 

 pression of the nectaries is a further indication of divergence from 

 the normal course of development of the bracts at a very early stage. 

 Hundreds of the reduced involucres were examined at San Antonio 

 without finding any with normal functional nectaries, though the 

 position of the nectary usually is indicated by a prominence of 

 rounded form and reddish color. (PL II.) 



The reduction or partial formation of the involucres with abor- 

 tion of the flower buds is a peculiar phenomenon, pointing, no doubt, 

 to some abnormal physiological state of the plants that may result 

 from the persistent destruction of the floral buds by the boll weevil. 

 Though the abnormal reduced involucres are not confined to boll- 

 weevil cotton, but are of occasional occurrence outside the weevil 

 belt and in many kinds of cotton, they have not attracted attention 

 or been reported as a regular feature, as in the late-season growth 

 of boll- weevil cotton. 



WEEVILS SHELTERED BY LARGE PLANTS. 



The size and form of the plants largely determine the condition of 

 the fields in relation to the boll weevil. With the ground shaded by 

 the heavy foliage of overgrown plants, conditions are favorable for 

 the multiplication of the weevils. The lanes are closed between the 

 rows of large plants, so that fields of boll-weevil cotton are covered 

 with a complete canopy of foliage, giving protection to the weevil 

 larvae in the flower buds. The weevil-infested buds that have fallen 



