190 Scientific Proceedings, Royal Dublin Society. 



that of the embryo. No Ijundles traverse the central regions of the haustorium, 

 as thej^ do in Lodoicea. 



The tissues of the margin and distal aspect of the haustorium retain their 

 meristematic phase later than those towards the proximal aspect, so that in the 

 earlier stages of germination cell and nuclear divisions are frequently found 

 in the fundamental tissue there, and among these dividing cells the bundles are 

 represented by procambial tracts. From these latter the tracheae are developed 

 earlier than the sieve-tubes. 



When the haustorium expands in size it becomes bilobed, and the lobes turn 

 over and overarch the depressed central concavity. In this condition the outer 

 surface is near the surface of endosperm, while the central mass of that tissue is 

 embraced by the haustorium, and is in contact with its inner surface. In the 

 middle of the haustorium, between its inner and outer surfaces, a large inter- 

 cellular space develops. During this enlargement the network of conducting 

 tracts, which at first had irregular meshes formed of sinuous bundles, becomes 

 more regular and the bundles straighten. Meanwhile the surface becomes 

 corrugated and papillose. 



In the younger stages of germination the epidermis of the haustorium is 

 composed of approximately cubical cells, with dense and finely granular contents, 

 which almost entirely fill their cavities. A large nucleus is visible. They present 

 the appearance of the secreting cells of a columnar epithelium (fig. 19, PI. XI, 

 ep.). As the haustorium enlarges, their vacuoles grow and their protoplasm 

 becomes more scanty, and loses its affinity for stains. At the same time the 

 nucleus diminishes in size, and its granules become less conspicuous (cf. 10). 



The bundles in the haustorium lie extremely close to its surface, so that 

 their outer elements are often separated from the epidermis bj^ one or two layers 

 only of cells. As in the case of Lodoicea, the ratio of the area of the cross- 

 section of the phloem in the haustorium to that of the xylem is much greater 

 than that in the petiole. In this case the ratio is about 5 : 1 in the haustorium 

 and 1:1 in the petiole (figs. 18 and 19, PI. XI). There are about twenty 

 elements in the phloem both of the haustorium and of the petiole ; about ten of 

 these are sieve-tubes. In the xylem there are about four in the haustorium and 

 twenty in the petiole. 



In the haustorium the sieve-tubes are comparatively wide (001-0003 mm. in 

 diam.), and their walls stain deeply with haematoxylin. Their length is 006- 

 009 mm. They occupy the outer part of the phloem strand, and are separated 

 from the xylem by several layers of eambiform cells. The tracheae of the 

 bundles are few, and have a diameter of 003-001 mm. 



Phcenix canariensis and P. silvestris. 



Later stages of germination were observed in these two palms. In the 

 example of the first-named species which was examined there were 8-10 bundles 

 in the transverse section of the petiole of the cotyledon. In that of P. silvestris 

 there were onlj'- 6. Between some of these bundles there were reduced bundles 

 (2 or 3 in all), consisting of fibres only, like those found in Lodoicea sechellarum. 

 These died out before entering the haustorium. As in Lodoicea and in P. dacty- 

 lifera, the strong sheath which accompanies the bundles in the petiole ceases 

 immediately as the bundle enters the haustorium. In none of the three species 

 of Phcenix did bundles cross the central tissue of the haustorium ; as they enter 

 it they diverge and bifurcate, keeping close to its surface. Then turning over 

 its margin and arriving on its concave surface, they converge and re-unite to 

 form a network on its distal aspect (fig. 15, PL X). 



