H. BOTANY AND HORTICULTURE. 367 



of growth of the vine and prolong its existence, as in the 

 case of chloride of potassium ; while others cause the plant 

 to wither, as in creosote and carbolic acid. Bromide and 

 iodide of potassium seem to act in the same manner as chlo- 

 ride of potassium. Chloral hydrate exercises a very poison- 

 ous influence, destroying the branch vine in three days, the 

 effect differing: from that of carbolic acid. One of the most 

 curious phenomena is that which is exhibited in the fall of 

 the leaves. In some instances the petiole becomes detached 

 at the point where it is inserted in the branch. This takes 

 place with such substances as bi-chloride of mercury, and 

 chloride, bromide, and iodide of potassium. In other cases 

 it is the limb which separates from the extremity of the pet- 

 iole. This occurs with ordinary water, and the nitrates of 

 ammonia, potash, and soda. In one single instance both 

 forms of observation have been observed under the influence 

 of the same substance. Sometimes, again, the branch dies 

 while the leaves continue to adhere to it. This is the case 

 after the use of hydrocyanic acid and the essence of turpen- 

 tine. Chloride of potassium acts as an invigorating and 

 preserving agent, quite exceptional in its character. A cur- 

 rent of ammonia allows the branch to preserve its freshness 

 for eight days, after which it withers. 1 B^Dec. 20, 1874, 189. 



HEAT AND VEGETATION. 



In some remarks on the relation between heat and vesre- 

 tation, which are translated by Firket from the work of 

 Kabsch on the "Vegetation of the Earth," the latter states 

 that the three fundamental laws of vegetation are as fol- 

 lows : First, for each plant there exists a maximum and a 

 minimum temperature, between which this species is capa- 

 ble of normally exercising its vital functions; second, in the 

 germination of grains, the opening of buds, the maturing of 

 fruit, each has need of a certain average degree of tempera- 

 ture, which may be very different according to the species 

 of plant ; third, each species of vegetable, in order to go 

 through the various phases of its existence, needs a certain 

 sum total of heat, and it is only in the localities where this 

 sum total is furnished every year, and where the conditions 

 of humidity and the constitution of the soil are equally fa- 

 vorable, that the existence of the plant can be regarded as 



