ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 207 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 Including' Cell-contents. 



Picro-nigrosin.* — 0. F. Curtis and R. H. Colley indicate the great 

 value of Picro-nigrosin as a combined fixative and stain for demon- 

 strating the finer structure of small algse, etc. It is prepared by 

 saturating a saturated aqueous solution of picric acid with (Iruebler's 

 water-soluble nigrosin. There is no danger of overstaining or over- 

 fixing. The excess is removed by rinsing in water or diluted alcohol. 

 The stain is insoluble in strong alcohol ; and it keeps well in Venetian 

 turpentine or l)alsam. It is an exceptionally transparent stain, and 

 differentiates the nuclear structure in cells with dense cytoplasm. 



Structure and Development. 

 Veg-etative. 



Morphology of Lemna Frond.-j-— F. H. Blodgett publishes a paper 

 in which an effort is made to show what structural units contribute 

 to the formation of the frond of Lemna. This frond is a reduced 

 structure especially adapted to vegetative propagation in water ; it 

 results from the action of two factors, viz. the film-tension of the 

 water and the upward thrust due to buoyancy. The roots act as a check 

 against free movement and tend to orient the plant when immersed by 

 sudden shock. The frond consists of a terminal leaf ; a bud enclosed 

 by a bud-scale, the base of which is fused to the base of the leaf and 

 to the stem ; and an apical region giving rise to new fronds. The lack 

 of space for vertical growth causes the outgrowth from the apical region 

 to assume a horizontal series, the successive individuals overlapping 

 each other in a confused manner. 



"Bars of Sanio" in Cycads.J — H. B. Sifton has studied the 

 structure of the xylem of the vascular bundle found in the petiole of 

 Cycas revoluta, and finds that the thickenings in the primary wall, 

 known as the " bars of Sanio," and hitherto thought to be absent in 

 the Cycads, are very distinctly marked. These "bars" are distinguished 

 by two features, viz. the close adherence to the borders of the pits and 



* Amer. Journ. Bot., ii. (1915) pp. 89-92. 



+ Bot. Gaz., Ix. (1915) pp. .383-90 (1 pi. and 1 fig.). 



X Bot. Gaz., Ix. (1915) pp. 400-5 (1 pi.). 



