256 MR. A. S. HORNE — A CONTEIBUTION TO 



(PI. 29. fig. 62), At the time of megaspore formation in the ovule each cell of the 

 plate is filled with a finely reticulate cytoplasm and contains a resting nucleus. The 

 nucleus subsequently divides to form two or four daughter nuclei, which are evident 

 during the early stages of endosperm formation in the young seed, but soon disintegrate 

 (PI. 29. figs. 63, 64). 



Course of the Vascular Tissue. 



The vascular structure of the flower-stalk of Leycesteria formosa separates into an 

 inner or axial (Text-fig. 2, Al) and an outer or peripheral series of bundles. The 

 bundles of the outer series extend upward in the wall of the ovary — those alternating 

 with the loculi toward the stamens {st\ those opposite the loculi toward the petals {'pe 

 and emerge from the terminal neck-like portion into the stamens and petals without 

 entering into connection with the axial vascular strands. The presence of a sin 

 peripheral series of bundles is a feature which is constant for all the Caprifoliaceae — 

 in Aralia two distinct peripheral series are present, an outer relating to the perianth and 

 stamens, and an inner composed of the dorsal and lateral carpellary bundles. But 

 the number of bundles in the series is not constant : there are ten in Leycesteria, 

 being equal to the sum of the petals and stamens; but in Linncea (CI) and Dier- 

 villa (Text-fig. 3, H) they are less than the sum, and only one-half the sum in Viburnum 

 (Text-fig. 4, B, a, b, c, d, e). 



The inner axial bundles are numerically equal to and alternate with the loculi in 

 Leycesteria. They extend axially upward into the parietal placentae (Text-fig. 2, A 2, ax) 

 and finally into the style, where they alternate with the lobes of the stylar canal, as 

 shown in C 3 (Linncea). A similar grouping of the axial bundles obtains in the remaining 

 genera. In Lonicera, where the ovary is trilocular, there are three axial bundles (B). 

 In Sai7ibucu8, where the number of loculi varies from two to five, there is a corresponding 

 variability in the bundles. In Aralia the absence of a loculus involves the absence of 

 the corresponding axial and of the inner peripheral ovarian bundles, but in Sambucus 

 only the axial bundles vary correspondingly. 



Two ranks of 



of Leycesteria. It follows, therefore 



each axial bundle (such as, for instance, axl in Al) is adjacent to the rows of ovules 

 {ov 1, ov 2'), the nearer series of each of the adjacent loculi, and receives corresponding 



of 



from each row. Each ovule receives 



single bundle. A similar arrangement obtains in relation to the ovules in the pluri- 

 ovulate loculi of Symphoricarpus, but the single ovnle in each uniovulate loculus receives 

 two connections, being in this respect the equivalent of a pair of ovules in the adjoining 



compartments. The vascular structure of the single ovule in Sambucus is similar to 

 this. 



Special attention has been given to the vascular structure of the flower of Viburnum, 

 on account of its peculiar morphology. The floral vascular skeleton has been recon- 

 structed from serial sections in a wax model (PI. 30). This model will now be described, 

 but the description should be followed with the aid of the diagrams of transverse sections 



