CA LA MA RIEA E. 



every rib ; but Stur says that where the preservation was more than usually 

 good, he has found two of them one above the other on the extremity of 

 the rib on the one side of the node. They sometimes appear in the form 

 of small attached cylinders of regular form 1 , from which the usual state of 

 preservation as produced by pressure can be readily deduced. 



In by far the greater number of cases the two rows of small knobs are 

 not preserved with equal distinctness ; very often one only can be clearly 

 seen, the other being imperceptible or only just indicated. If now we 

 would know whether the position of the more distinct line of knobs is a 

 fixed one, or whether sometimes one sometimes the other line may be 

 more prominent, we must for the reasons given above confine ourselves 

 entirely to the examination of branched specimens in which the direction 

 of growth is absolutely known. The theoretical considerations which have 

 determined the views of authors must be reserved for future notice. I have 

 examined all the figures of the kind with which I am acquainted, and have 

 found that in almost all cases the more apparent line of knobs corresponds 

 to the upper end of the lower internode, and this agrees with the direction 

 usually assigned to the fragments of stems of Calamitae and adopted also by 

 Weiss. In Stur's figure 2 only I find the opposite arrangement; both lines 

 are present, but the line at the lower end of the upper internode is much 

 the more prominent. As there is no reason whatever for doubting the 

 exactness of this very excellent figure, I conclude that no absolute rule can 

 be laid down for the position of the stronger line of knobs, but that in case 

 of doubt Weiss' view is to be preferred as the more probable to the opposite 

 view represented by Brongniart and Stur. 



Brongniart 3 originally attempted a morphological explanation of these 

 small knots, and Stur 4 has recently turned his attention to the same subject. 

 Stur takes his stand, and rightly, on the comparison with the similar course 

 of the strand in Equisetum ; but at the same time he falls into a serious 

 error which affects all his further conclusions, and unfortunately makes 

 them in my judgment entirely worthless from the botanical point of view. 

 It is an axiom with him, that the small protuberances correspond to the 

 points of attachment of leaves, buds and roots, and are therefore direct 

 indications on the cast of the respective positions of these organs. But 

 there are various objections to this view. It is obvious that projections on 

 the cast of a medullary cylinder can only arise where there are corresponding 

 depressions in the organic substance immediately surrounding it. Hence 

 if there has been no disappearance of tissue in the environment to cause a 

 depression of the kind, the emergence of the vascular bundle in the direction 

 of the lateral members cannot of itself leave any trace behind it on the cast. 



1 Weiss (5), t. 17, f. 5. 2 Stur (5), p. 192, f. 18 and t. 23, f. 2. 3 Brongniart (1) 



4 Stur (5). 



