INTERCELLULAR SECRETORY RESERVOIRS. 44I 



Any other form of tissue, and any region may contain secretory passages, even 

 the primary xylem of the bundles. Still in this relation also the phenomena are con- 

 stant, according to species and groups, while in individual cases all possible com- 

 binations occur, as is obvious from the following synopsis of the most important 

 known examples, and from the works therein cited, which are to be compared for 

 further details. For the sake of clearness, and in order to avoid repetitions, the 

 secondary changes belonging to the subjects of Chaps. XIV and XV will often be 

 mentioned in the following pages. 



The mucilage-canals of the Marattiacea ^ traverse the parenchyma of the pith and cortex 

 of the stem in great numbers, and branch and anastomose frequently. They are con- 

 tinuous from the cortex into the roots, in which they pursue a directly longitudinal course 

 towards the apex, and here end in the meristem ; and into the foliar organs, having a 

 similar straight course in the petiole and rachis, with few branches and anastomoses. 

 Their endings in the foliar organs have not been exactly investigated ; thorough descrip- 

 tions of their course in the segments of the lamina are also wanting. 



The leaf of Lycopodium inundatum (also of L. alopecuroides) ^ is traversed on the pos- 

 terior side by a mucilage-canal, which runs from apex to base : here it enters the cortex 

 of the stem for a short distance, and there ends blindly. The mature canal is limited, as 

 in Marattia, by closely-connected cells of the adjoining parenchyma, but irregular club- 

 shaped cells are seated upon the latter, which project like hairs into the cavity of the 

 canal. In the young leaf these cells form a strand 4-5 rows thick, where the future 

 canal will be, and they have the form of angular meristematic cells ; as the leaf unfolds 

 they separate from one another, while the surrounding tissue extends to a corresponding 

 extent, and they elongate to a club-shape, while the mucilage appears between them. 

 They thus constitute the epithelium of the passage, which is still more dissociated than 

 that in Marattia. A similar small passage is found in the marginal expansions on the 

 dorsally winged ridges of the leaves of the spike in L. annotinum. 



In the stem of the Cycadesi mucilage-passages are also distributed through the paren- 

 chyma, in specially large numbers in the cortex : they have branchings and anastomoses. 

 But branches from those of the stem always pass into the leaves, and there end. They 

 traverse the petiole and rachis of the pinnate leaves longitudinally, in varying number 

 according to species and individual — in one small leaf of a seedling of Zamia longifolia 

 I found, e. g. in the petiole only two, in the larger leaves of stronger plants they are 

 numerous, and their distribution in the parenchyma is generally irregular. They enter 

 the pinnsE only in forms of Dion, Encephalartos, and Stangeria', in the first genus running 

 sometimes above the vascular bundles, in Encephalartos between them, and indeed alter- 

 nating regularly with the parallel vascular bundles in the same plane with them and at 

 equal distances ; in the pinna of Stangeria they lie above and below the vascular bundles 

 of the rib, without passing out laterally into the lamina. In the specimen examined one 

 central bundle, and one lateral one near it on either side ran into the rib. One mucilage- 

 passage lies between the middle bundle and the upper epidermis, and one on each side 

 between the lower epidermis and the gap which separates the middle one from the 

 lateral bundles. 



Among the Conifers all investigated species, with the single exception of Taxus, have 

 resin-passages or resin-reservoirs, which vary in distribution and number according to the 

 species. 



Starting from the leaves*, in those examples which have one median vascular 

 bundle or pair of bundles— as in the investigated species of the Cupressineae, Sequoieae, 



• Halting et de Vriese, Monogr. des Maratt. — Frank, /. c. 



'^ Hegelmaier, Botan. Zeitg. 1872, p. 844. 



' Kraus, Cyci?,(Jeenfiedern, I.e. p. 328. ' Thomas, Coniferenblatter, I.e. 



