. Plant studies; an elementary botany. Botany. 36 PLANT STUDIES framework of veins is variously arranged. The large veins which enter the hlude send off smaller hranches, and these send off still smaller ones, until the smallest veinlets are invisible, and the framework is a close network of branching veins. This is plainly shownljy a ""skel- eton" leaf, one which has been so treated that all the green sub- stance has disap- peared, and only the network of veins remains. It will be noticed that in some leaves the veins and veinlets are very prominent, in others only the main vei
. Plant studies; an elementary botany. Botany. 36 PLANT STUDIES framework of veins is variously arranged. The large veins which enter the hlude send off smaller hranches, and these send off still smaller ones, until the smallest veinlets are invisible, and the framework is a close network of branching veins. This is plainly shownljy a ""skel- eton" leaf, one which has been so treated that all the green sub- stance has disap- peared, and only the network of veins remains. It will be noticed that in some leaves the veins and veinlets are very prominent, in others only the main veins are prominent, while in some it is hard to detect veins (see Jugs. X\i, 20). :!U. Significance of leaf veins.âIt is clear that the frajiiewoi-k nC \-cins is doing at least two tilings for the blade: (I) il siipiiDi'ts the s]iread mxt green suli- ; anil (".') it I'undui.'ts material to ^ind IVoiu the screen substan(_;o. So complete is the network (.)f \eins that this. Fig. 20. A ](\if of hawthorn, showing a short petiole, and a broad lootlicd blade with a conspiciiouB network of ^â einH. Note tln^ relation between tlie veins and the tei'tli.âAfter Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Coulter, John Merle, 1851-1928. New York, D. Appleton and Company
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