TRANSACTIONS OF TIIE SECTIONS. 105 



representative of the Order G9, Umbelliflorge, is Araliophyllum in the Chalk. The 

 Araliaceae have variable characters, as shown by the formula, Cas-i)o) C05-10 

 A115-10 Gii(2^To), a formula which will include that of the Uinbellifenc, viz. Cas 

 ( '0.3 Alio Gu(2). 4th. That while the Monocotyledons are undoubtedly mono- 

 phyletic, the Dicotyledons are certainly polyphyletic ; hence the great difference 

 seen hi the formulae of these flowers. 



On the Movements of Water m Plants. By Prof. M'Nab. 



In some experiments published some time ago by the Royal Irish Academy, a 

 rapidity of ascent of water in the xylum of the stem of the'Cherry Laurel, equal 

 to 40 inches per hour, was observed. Since the publication of those experiments, 

 numerous other experiments have been performed by Professor Pfitzer of Heidel- 

 berg, with the view of ascertaining the velocity of ascent of fluid in plants. 

 Pfitzer first experimented by observing how soon leaves that had become flaccid 

 from want of water reassumed their normal position. He also tried the lithium- 

 citrate method, and in a third series combined the two, using the one method as a 

 check on the other. In his experiments with lithium citrate, Pfitzer has observed 

 the greatest rapidity of ascent yet recorded, the Helianthus animus being found 

 to give a velocity equal to 22 metres per hour, or 15 inches per minute. Professor 

 Pfitzer also describes a new method to supersede lithium and the spectroscope, 

 and suggested to him by Professor Kohne, namely, a solution of soluble indigo- 

 carmine (4 parts to 1000 of water). Experiments made with this solution have 

 been perfectly successful. 



Hoehnel, in his recently published dissertation, ' Ueber den negativen Druck 

 der Gefassluft,' has shown that the air in the vessels of the xylum of rapidly 

 transpiring shoots is in a state of diminished tension ; and when such a shoot is cut 

 under mercury, the mercury will rise in the stem from 20-38 centimetres in a few 

 seconds. From his experiments he concluded that the diminution of the tension 

 of the air in different plants was as follows : — 



Quercuspedunculat.a .... 24-5 centimetres of mercury. 



sEsculus hippocastamim . . 37'0 „ „ 



Syringa vulgaris 24'0 „ ,, 



tllmus campestris 20'0 ,, „ 



Helianthus 4G - „ „ 



From this it is evident that an important source of error may be introduced into 

 all experiments with lithium or coloured solution or cut shoots, as this abnormal 

 current, as Pfitzer calls it, may be more rapid than the normal. Experiment, 

 however, shows that the normal current is more rapid than the abnormal, due to 

 the diminished tension of the air in the vessels, hence no error has been introduced 

 into the experiments from this cause. 



On an abnormal Plant of Primula veris. By Professor M'jSab. 

 A plant of Primula veris was picked in a field on the east side of the Hill of 

 Howth, co. Dublin, in April 1877, having in the axil of one of the older and 

 outer leaves a single flower of Primula vulgaris. The plant had the leaves of tho 

 Cowslip, as well as two umbels of flowers of P. veris, both arising from the axils 

 of the younger or inner leaves. One of the umbels had the flowers expanded, the 

 other had_ only small buds. The single primrose flower was in all respects normal, 

 and both it and the cowslip flowers were macrostylous. In the field along with 

 the abnormal plant both P. veris and P. vulgaris were common, as well as occasional 

 plants of evident hybrid origin. The abnormal plant exhibited was probably a 

 hybrid showing the return to the parent forms, much in the same manner as the 

 well-known Cytisus Adami. Mr. Darwin, in his last book on the forms of flowers, 

 mentions the occurrence of such a form as that here described in cidtivated hybrids 

 between the cowslip and primrose. It is therefore a matter of much interest to 

 find that similar forms may be produced in a wild state. 



