106 BOTANY. 



Water-pores nearly like those of the fuchsia occur ou some species of 

 Samfrcbga, Heuchera, Mitella, Aconitum, Vilphmium, Samiucus, and 

 many olber plants. 



Another form, more closely resembling the ordinary stomata (but of 

 much larger size), occurs on Tropasolum Ldbhianum, Rocliea eoccinea, 

 and others. 



§ III. The Fibeo-vasculak System. 



133 In most of the higher plants portions of the pri- 

 mary meristem early become greatly differentiated into 

 firm elongated bundles, which traverse the other tissues. 

 They are composed for the most part of tracheary, sieve, 

 and fibrous tissues, together vi^ith a varying amount of pa- 

 renchyma. These elementary tissue s have, with some con- 

 siderable variations in the different groups of plants, a gen- 

 eral similarity of arrangement and aggregation throughout 

 the Pteridopliytes and Phanerogams. In a comparatively 

 small number of cases laticiferous tissue is associated with 

 the above-mentioned tissues. To these aggregations of tis- 

 sues the name of Fibro-vascular Bundles has been given.* 



134. — In many plants the fibro-vascular bundles admit of 

 easy separation from the surrounding tissues; thus in the 

 Plantain {Plantago major) they may readily be pulled out 

 upon breaking the petioles. In the leaves of plants, where 

 they constitute the framework, they are, by maceration, 

 readily separated from the other tissues as a delicate net- 

 work. In the stems of Indian corn the bundles run through 

 the internodes as separate threads of a considerable thick- 

 ness. 



135. — It is impossible to fix upon a particular form as the 

 type of the fibro-vascular bundle. It should be understood 

 at the outset that the similarity between the bundles of 

 widely separated groups of plants is only a general one, and 

 that there are great differences in the details of their struc- 

 ture. It must further be borne in mind that these bundles 

 are not themselves tissues, but aggregations of dissimilar tis- 



* They are also called Vascular Bundles ; this term ought, however, 

 to be retained for those reduced bundles in which only vessels are pres- 

 ent — e.g., in the veinlets of leaves. 



