204 STECKBECK— ON COMPARATIVE HISTOLOGY 



temperature to initiate the movement. The maximum angle through 

 which the secondary leaflets of this tree move is less than that of the 

 black locust. The writer was unable to get any visible response in the 

 leaflets to mechanical stimuli, but noted a slight drop of the secondary 

 leaflets when 50% sulphuric acid was applied to the tertiary pulvini. 

 The primary pulvinus of the leaf is not well defined, appearing as a 

 slightly swollen, clasping leaf base, and shows no irrito-contractility 

 when stimuli are applied to it. 



Leaf. The crystals in the secondary leaflets are found along the 

 veins and are arranged in discontinuous lines. A single line is present 

 along the smaller veins. With an increase in the size of the veins 

 there are introduced additional ranks of crystals until in the midrib 

 there are present 7 to 9 broken rows of crystals. The crystals vary 

 considerably in shape and size, with the four angled prismatic type in 

 greatest abundance, and among these relatively few hexagonal prisms. 

 The latter in some cases indicate a very faint line across the middle of 

 each crystal. The hexagonal forms are rather small, with an average 

 length of 12.3 microns and a width of 6.83 microns. Conglomerate 

 crystals -are present in the bundle of the midrib, but none in the meso- 

 phyU of the leaflets. 



Pulvini. Two kinds of crystals are present in the tertiary puKini — 

 the quadrangular type noted in the leaflet bundles, and an abundance 

 of conglomerates The regular prismatic forms are found in the endo- 

 dermal region, the lines being continuous from the midrib bundles. The 

 conglomerate crystals are found in the cortex of the pulvini, where they 

 occur in greater number on the dorsal side of the pulvini, and are also 

 present in the vascular bundles. 



In secondary pulvini the crystal relation is similar to that described 

 for the tertiary pulvini (Plate LX, Fig. 6), and the same is true for the 

 primary pulvinus, but here very few crystals are present. Of the regular 

 prismatic type, none indicated the hexagonal form. 



Petiole. In the secondary petioles we again note the regular pris- 

 matic' crystals arranged in fairly continuous lines in the endodermis. 

 As in the leaflets, the shape of the crystals varies, with here and there a 

 hexagonal crystal present. Conglomerate crystals are also present in 

 the inner cortex and in the vascular bundles. These, like the prisms, 

 show variation in shape, with transitions toward the prismatic forms. 

 The crystal distribution in the primary petiole of each leaf is similar to 

 that in the secondary petioles, with fewer crystals relatively and more 

 breaks in the lines of crystals than in the secondary petioles. 



