136 BOARD OF AGRICULTURE. 



I have endeavored to sketch briefly the chief facts of vegetable 

 anatomy, or rather histology, in order to show you that the laws 

 governing the hygiene of the plant are extremely simple. We 

 have incidentally seen that the functions of the parts of the plant 

 are plainly recognized ; that of the root to imbibe sap and gaseous 

 food, that of the stem, whether above or below ground, to convey 

 it, that of the leaves to work it over into food for the plant, that 

 of the flower to produce seed to reproduce its kind. These simple 

 facts constitute the physiology of plants. It would be very 

 pleasant to me to depart at this point from the line of study 

 marked out, and call your attention to some of the curious facts 

 in vegetable physiology. It would be interesting to notice the 

 phenomenon of increased heat at the time of flowering, and the 

 obscure motions of many water plants, and the startling but still 

 more mysterious flashes of light emitted by some flowers. It 

 would be entertaining to observe the peculiar irritability of many 

 plants, as for instance, the fly-trap, which grows in our southern 

 States, and the more delicate sensitive plant. These irritable 

 plants, which recoil from the touch, can be etherized, and be made 

 to become perfectly insensible to even the rudest violence. But 

 these facts lie out of our path at present, and we must therefore 

 pass on to study plant-pathology. 



We will for the sake of system, arrange plant-diseases into three 

 great classes. 



First, Those which result from mechanical injuries. 



Second, Those produced by flowerless parasites. 



Third, Those arising from improper or insuflScient plant-food. 



First, Those which result from mechanical injuries. 



These may be produced by flowering parasites and by animals. 

 The only flowering parasite which proves destructive to field crops 

 in New England, is a salmon-colored vine which climbs over the 

 stalks of clover and various grasses. This leafless vine belongs 

 to the same botanical family as the sweet potato and the morning 

 glory. The plant has vciy small flowers, which bear four seeds 

 ripening in autumn. Those slender vines twist around the stalks 

 of clover and strangle them. The plant is called Cuscuta, or 

 Dodder, and it is divided by Botanists into many species. One of 

 these species is usually found with flax, and it is therefore named 

 flax Dodder. The plant is termed a parasite. A vegetable para- 

 site is a plant which lives at the expense of other plants, drawing 

 all its nourishment from its unfortunate neighbors. The seed of 



