VIII Journal of Agricultural Research voi.xii 



Plate 34. Larvae of su-eet-potato weevils: A. — Cylas formicarius elegantulus, page 

 Victoria, Texas, lateral view. B. — Same, dorsum of head. C. — Same, 

 face. D. — Same, side of head. E. — Eusccpes batatce, Barbados, dorsum 

 of head. F. — .Same, face. G. — Same, side of head. H. — Same, lateral 

 view of larva 612 



Steriutv IX THE Strawberry 



Plate B. Minnesotii 3: i. — Pollen mother cell previous to synapsis. 2. — 

 Presynapsis in the pollen mother cell showing loops extending out from 

 synaptic mass. 3. — Two loops and portion of a loop extending from the 

 presynaptic mass. Same stage as figure 2. 4. — Synapsis in a pollen 

 mother cell. 5. — A postsynaptic stage. G.^Open spireme stage. 7. — A 

 presegmentation stage of the spireme. 8. — A portion of a bivalent spireme 

 thread of the same stage as figure 7. 9. — Segmentation of the bivalent 

 spireme into chromosome pairs. 10. — A portion of the bivalent spireme 

 during segmentation. 11, 12. — Chromosome pairs during the contraction 

 period following segmentation. 13. — Individual chromosome pairs show- 

 ing various figures commonly formed diu-ing contraction. 14. — Diakenesis 

 in the pollen mother cell. 15. — Multipolar spindle stage of pollen mother 

 cell. 16. — -Early anaphase of the heterotypic division 670 



Plate C. i. — Late anaphase of the heterotypic division. 2. — ^Chroraosomes 

 on the equatorial plate of the homeotypic division. 3. — A portion of an 

 anther in the tetrad stage, showing the microspores embedded in the 

 gelatin-like sheath. 4. — A tetrad at the same stage as those shown in figure 

 3. 5. — A microspore shortly after liberation from the tetrad. 6. — A 

 liberated microspore in which growth has commenced. 7. — A later stage 

 than figure 6, showing the slight thickening of the wall and the irregularities 

 due to grov^lh of the wall. 8. — Microspore growth completed previous to 

 division of the microspore nucleus. 9. — A section through a microspore 

 nucleus in prophase showing the continuous univalent spireme. 10. — 

 Another section of the same nucleus, showing the first stages of the disappear- 

 ance of the nucleolus. 11. — Metaphase of the division of the microspore 

 nucleus. 12. — F. virginiana. Anaphase in the division of the microspore 

 nucleus. 13. — Telophase of the division of the microspore nucleus. 14. — 

 A later stage than figure 13 in which the generative cell has been definitely 

 cut off. 15. — A young pollen grain shortly after division, showing an in- 

 crease in cytoplasm content. 16. — End view of a pollen grain showing the 

 pattern of the laminate layers shown in figure 15 and Plate D, figures i, 6, 

 and 15 670 



Plate D. i. — Nearly mature pollen grain. 2. — Mature pollen grain. 3, 4, 

 5, 7. — Various types of degenerate microspores from anthers bearing micro- 

 spores of the stage shown in Plate C, figure 6. 6. — An aborting microspore 

 from an anther containing half-grown microspores. 8. — An aborting micro- 

 spore of the same type as that shown in figure 6 from an anther containing 

 nearly full-grown microspores as in Plate C, figure 8. 9, 11. — Microspores 

 of the same types and same age as figures 6 and 8, in which degeneration 

 has proceeded farther. 10. — An aborted microspore from an anther con- 

 taining microspores of the stage sho\\'Ti in Plate C, figure 8. 12. — An early 

 stage of degeneration in a full-grown i-nucleate microspore. 13.— An 

 early stage of degeneration in a full-grown i-nucleate microspore. 14. — 

 An aborting microspore containing an abnormally small amount of light 

 staining cytoplasm; from an anther containing i- and 2-nucleate micro- 

 spores. 15. — An aborted microspore from an anther containing i- and 

 2-nucleate microspores. 16. — An aborted microspore containing very 

 scant cytoplasm. The nucleus has completely degenerated and degenera- 

 tion of the cytoplasm has begun 670 



