o/ Latliraea clandcstina. 413 



towards the exterior, more delicate, and at the sides thinner in 

 the internal part in contact with the exterior of the wood. 



In no part has M. Duchartre been able to detect proper or 

 laticiferous vessels. 



But if the zone of elongated ligneous tissue forming the wood 

 and the liber constitutes a continuous cylinder around the pith, 

 and not a series of distinct fascicles separated by the medullary 

 rays, as is usually the case, it is not less true that the vessels 

 there form separate fascicles and of a definite number. This 

 is shown by the researches of M. Duchartre on the successive de- 

 velopment of the stem and the tissues which constitute it. The 

 vessels form at first four quite distinct fascicles ; they then divide 

 into a greater number, and we count eight, ten, twelve, and even 

 more ; lastly, the vessels appear dispersed with iiTcgularity in the 

 whole of that zone, which itself, on old stumps of at least two 

 years, acquires a much greater thickness, and is often formed of 

 two distinct concentric layers. 



Thus, notwithstanding these two essential points, by which the 

 stem of the Lathr<2a clandestina difiers from the ordinary struc- 

 ture of Dicotyledons, the absence of spiral vessels and of the 

 medullary rays, its growth is effected according to the mode 

 proper to the totality of these vegetables. 



The root, in its principal parts and even in its fibrils, presents 

 the same structure as the stem, modified, as is generally the case, 

 by the absence of the pith ; but the parasitism of the plant gave 

 a peculiar interest to the investigation of the extremities of the 

 radical fibrils by which it is fixed on the roots of trees, and most 

 frequently on those of the poplar. 



This point however, which has been already examined carefully 

 by Mr. Bowman, in Lathraea squamaria, could present fewer 

 new facts ; indeed the differences between these two species in 

 this respect are very slight, and M. Duchartre has only been able 

 to add some details and to point out some secondary differences 

 between these two plants. 



The L. clandestina attaches itself to the roots of trees by nu- 

 merous suckers terminating in radicles, or growing laterally along 

 these fibrils and representing spongioles. These suckers, nearly 

 hemispherical, are larger than those of Lathnea squamaria ; their 

 surface of adherence is plane or slightly concave, formed of a cel- 

 lular tissue of a peculiar form, elongated and directed perpendi- 

 cularly on the external surface. The small tubercle which the 

 sucker itself forms is essentially cellular, but traversed, especially 

 toward its centre, by numerous moniliform vessels with reticu- 

 lated sides, which however do not extend as far as the surface by 

 which the sucker is applied on the foreign root ; an arrangement 



