42 CACT^, OR PRICKLY PEARS. 



layer, occiiiiying cells lying directly V)elow the e])iderinis ;. 

 other ueeclle-shaped crystals of similar or nearly similar 

 composition are to be found in the cell walls of cortical 

 and deeper layers. The vascular strands are also 

 protected on each side, in many species, by other cell& 

 filled with spheeroraphides. Not only are these crystals 

 a kind of protective armour whose sharp points repel the 

 attacks of insect larv;Te*, of coccids, and other soft-bodied 

 creatures, but the cells containing them .seem to be avoided 

 by fungi. In making sections of Cacti so protected, each 

 of the two workeis found the knives of their microtomes 

 rapidly blunted, and far more difficulty was experienced 

 in obtaining good sections than with any other vegetable 

 tissue. The needle-shaped crystals, true raphides. are 

 very abundant in our grass trees, and make the sectioning 

 of parts of those plants difficult ; but the sphere-crystals 

 or spha;rora])hides of the cortex of Opuntia offer far more 

 difficult v. 



3. — Plants Xattraliski) in QrEEXSLAXD. 



(Jmitting plants like the night-blooming Cereus. 

 C. grancUflnrus, which may occasionally be .seen climbing 

 over scrub or forest trees near a deserted homestead^ 

 the Barliadoes Gooseberry. Peireskia aculeata, already 

 mentioned, and species of Rkipsali.s. EchmocMtus, 

 Melocactits, and Mammillaria seen in our bush-houses,, 

 the introduced si)ecies that have fully established themselves^ 

 n our State belong to two genera. Nopalea and Opuntia. 

 In Nopalea the essential organs, the stamens and pistil, 

 protrude from the petals, which press closely around 

 them, or are connivent, as the botanist expresses it. In 

 Opuntia the essential organs are shorter than the petals, 

 which encircle them at a distance, together forming a 

 funnel-shaped corolla . 



The following table is a list of species likely to spread 

 with some of the localities from which they have been 

 reported : — 



♦Eraas' BoUny, \j. 93. 



