120 



CHARLES S. RIDGWAY 



and Avena sativa L. and on the newly formed roots of old plants 

 of Capriola dactylon L. 



The following dicotyledonous plants were examined and showed 

 the callose in their root-hairs in varjdng degrees: Pisum sativum L., 

 Eupatoriuni capillifolium Lam., Oxalis strida L., Vivna catjang L., 

 and Ipomea quinquifolia L. 



Most of the plants examined were taken from a greenhouse 

 bench filled with loam soil which had had a httle air-slaked lime 

 added. Plants of some of the above species, chiefly Bermuda 

 grass and species of Panicum, from other places were also exam- 

 ined and it was found that the callosed root-hairs occurred on 

 plants growing in cinders and in sand on benches in the green- 

 house and also in rich loam and in sandy soil near buildings out of 

 doors. 



Besides the occurrence of callose in its familiar location, namely 

 as pads closing the pores of sieve plates, it has been found by 



EXPLANATION OF PLATE. 



All drawings were made with the aid of an Abbe camera lucida with a Zeiss D. 

 and No. 8 compensating ocular combination. 



1 Callosed root-hair on old portion of root (3 cm. proximal to root tip). Cal- 

 lose formation took place at an early stage in its development. 



2 Distal end of an old root-hair, close to the one from which figure 1 was drawn, 

 showing partial plugs. 



.3 Distal end of a long, slender hair, showing closure of the lumen and inclusion 

 of protoplasm. 



4 Lumen of hair completely plugged by callose, protoplasm on both sides of 

 plug. 



5 Callose formation in distal end of root-hair only. 



6 Plug of callose in a large, old root-hair; the distal end breaking down and pro- 

 toplasm pro.ximal to plug only. 



7 Callose formation on radial wall of epidermal cell without root-hair. The 

 appearance of breaking down of adjacent cells was caused in making the prepara- 

 tion. 



8 Very young root-hair close to root tip showing strong callose formation. 



9 Irregular thickening by callose in root-hair of medium age. Cross sections 

 shown at right of figure, Semi-diagramatic. 



10 One of several examples of septate root-hairs. 



11 Representation of swelling effect upon callose of 1% caustic potash solution. 



12 Thickening of wall of root-hair bj- local formation of cellulose. 



