172 KANSAS UNIVERSITY SCIENCE BULLETIN. 



braced in thirty-nine families, sixty-five genera, and seventy- 

 two species. 



DRAWINGS. 



In general, camera-lucida drawings have been made to show 

 the pits in the phloem when found, to show sieve tubes and 

 some of the adjacent tissues from three points of view. A 

 Bausch and Lomb 1/12 objective was used with but few ex- 

 ceptions, and for measuring a Bausch and Lomb micrometer 

 eyepiece — divisions 1/10 mm. In all about 175 drawings have 

 been prepared for use in evidence. 



FINDINGS. 



Problem I. — What special devices occur for the lateral 

 transfer of food materials in the phloem ? 



After considerable search I have found pits in the lateral 

 walls of the phloem of fourteen plants, as shown, for example, 

 in figures 1 and 2. In figure 1 they are evidently between the 

 medullary ray and the phloem ; in figure 2, between the sieve 

 tubes and the adjoining cells. 



Frank* seems to imply that there are no pits between the 

 parenchyma cells of the phloem. Figure 1 shows some as they 

 appeared between the parenchyma and the parenchyma, and 

 between the parenchyma and medullary-ray cells of the stem 

 of Popultis alba. He also states that the sieve tubes are the 

 widest phloem elements.- This is hardly true in quite a num- 

 ber of instances, as in Amorpha fruticosa (fig. 6), where the 

 parenchyma is the wider. Quoting from Briosi,^ he states that 

 the slime bodies of the sieve tubes sometimes contain starch 

 granules. Some are shown in figure 7 in Populus alba. They 

 were noted also in Rhus toxicodendron. Frank states also^ 

 that the lateral walls of the sieve tubes are never strength- 

 ened. Figures 4 and 5 show thickenings on the lateral walls 

 of the sieve tubes in the roots of Populus deltoides. It would 

 seem that these are for strengthening the wall. They occur 

 also in the end plates of the sieve tubes of the same plant 

 (figs. 8 and 9) and in Populus alba. 



Strasburger'^ finds pits between the phloem parenchyma and 

 the medullary rays. Figures 1, 2 and 3 show such. He also 

 states® that the cortical rays are specially adapted by means 



1. Frank, A. B. : Lehrbuch der Botanik, 1892, vol. I, p. 184. 



2. Loc. cit., p. 183. 



3. Loc. cit, p. 183. 



4. Loc. cit., p. 183. 



5. Strasburprer, Ed., Textbook of Botany, 1897, p. 135. (Trans, by Porter.) 



6. Loc. cit., p. 186. 



