96 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of ammonium compounds and nitrates, but cliiefly of asparagin and 

 other amides ; and a substance of the nature of saccharose. The 

 alkaline reaction of the contents of the sieve-tubes is undoubtedly- 

 due to calcium phosphate. As much as 2 to 3 per cent, of phosphoric 

 acid was determined in the aqueous solution. The same is also true 

 of the alkaline reaction of other fluids found in plants, as, for example, 

 that in the glands of the " ice-plant," Mesemhryanihemum crystalUnum. 



Heterophylly of Quercus prinoides.* — According to Mr. T. 

 Meehan the leaves of this species of oak vary, from nearly orbicular 

 and obtuse to narrowly lanceolate or saliciform and acute ; some are 

 quite entire, while others have lobed and wavy edges. These varia- 

 tions can be due neither to environment nor to mere conditions of 

 growth or sexual peculiarities, but only to an innate and wholly 

 unknown power to vary, which science has been so far unable to 

 reach. 



Organs of attachment of Ampelopsis.f — ^Herr A. V. Lengerken 

 has examined the mode of formation of the structures by means of 

 which several species of Ampelopsis (Virginian creeper) attach them- 

 selves to their support. The irritation caused by the contact of the 

 apex of the tendril with the foreign substance first excites the epider- 

 mis to a characteristic growth; it then extends to the hypodermal 

 layer and subjacent tissues. The discs are found only on those 

 tendrils the apices of which are long in contact with foreign bodies ; 

 branches of the same tendrils not in this condition die off. With the 

 increased development of the discs, the tendril loses its power of 

 winding round foreign support. Those species of Ampelopsis which 

 produce these attachment discs show indications of similar structures 

 on the apices of still unchanged tendrils. In A. VeitcMi this can be 

 made out in the meristem of the tendrils at the earliest period. The 

 irritation caused by contact need not be vertical ; it may be oblique ; 

 in most cases the discs are formed on the convex side of the coiled 

 apex of the tendril. Two results follow from the irritation. A great 

 excretion of mucilage takes place, by means of which the disc can 

 become rapidly attached to the support ; and after this excretion has 

 taken place, the cortical tissue and epidermal cells inclose in their 

 growth the least projection on the surface of the support, thus causing 

 an extremely firm attachment of the disc. 



Absorbing Hairs of Dipsacus.| — Sig. G. Archangeli finds, in the 

 receptacles at the base of the leaves of JDipsacus Fullonum, no special 

 secretion, but only rain-water. He never found glandular hairs 

 provided with mobile threads of protoplasm, as described by Cohn 

 and F. Darwin. Hairs of a precisely similar character occur outside 

 these reservoirs on other species of Dipsacacese which do not form such 

 reservoirs, and on many other plants ; he believes them to be con- 

 cerned simply with the absorption of water, and to have no function 

 connected with the absorption and digestion of nitrogenous substances. 



* Proc. Acad. Nat. Sci. Philad., 1885, p. 365. 



t Bot. Ztg., xliii. (1885) pp. 337-46, 353-61, 369-79, 385-93, 401-11 (1 pi.). 



X Atti Soc. Toscana di Sci. Nat., iv. (1885) pp. 178-81. 



