EAPmDES AND PLANT CRYSTALS. 161 



investing the prism. In size they vary from l-25th inch, and thickness of 

 l-532ud inch, in the Florentine Iris, to a length of 1-lOOOth inch, and 

 thickness of l-6400th inch in the ovary coat of Centaurea nigra. 



These prisms are small but distinct in the ovary coat of many 

 Compositae, as the Thistle, Knapweed, &c., but large ones occur in many 

 exotic exogens, of which examples may be seen in the barks of 

 Quillaya and Guaiacum. They are frequent in endogens as in the 

 common purple Flag, and many other Iridaceae, and often appear in the 

 same plant with Raphides, as may be seen in certain Amarylhds ; they 

 can be well seen with polarised hght. 



Although the precise use of these crystals in the vegetable economy 

 is obscure, we may conclude that whatever is constant in a plant must ba 

 important. And when we consider how commonly plant crystals aro 

 composed of phosphate or oxalate of lime, or some other compound of 

 *his earth, and its value in the growth or nutrition of animals and 

 vegetables ; and that they are plentiful in many plants which form the 

 food of birds and mammaha, and food and medicine for man, we get a 

 ghmpse of the use of these crystals. Raphides are useful in systematic 

 botany in distinguishing between species. We can also easily see why 

 the gardener collects decayed leaves for his composts, and why such 

 plants as abound most in crystals are the most valuable for the pui-pose. 

 The above account has been compiled from various articles by Professor 

 Gulliver, in the "Microscopical Journal," "The Annals of Natural 

 History," and other scientiiic journals. 



METEOEOLOGY OF THE MIDLANDS. 



THE WEATHER OF APRIL, 1878. 



BY. W. J. HAKRISON, F.G.S. 



The weather of April last has elicited encomiums from nearly all 

 our obsei-vers. The first ten or eleven days were cold and frosty, tho 

 night of the 1st being the minimimi at nearly all stations. This frost 

 cut off the apricots, early plums, and gooseben'ies. After the 10th a 

 warm and genial period set in, which continued to the end of the month. 

 Easterly winds prevailed, but the barometer was by no means liit.'li. 

 Thunderstorms occurred on the 5th, 17th, 25th, and 30th. Rainfall 

 again below the average, the only stations whose maximum fall exceeded 

 one inch being Whitfield (l-25in.) and West Malvern (l'24in.,) both on 

 the 10th, which day px'oduced the extreme fall at several stations in the 

 west and in the south of England generally. In London on the 11th 

 from 2 to 2f inches fell in twenty-four hours, with a light easterly wind, 

 but this was quite local. In the midlands generally the 20th gave tho 

 maximum fall, though this was not of very large amount. This was a 

 very unsettled day, and marked by a change of wind from south-west to 

 east. 



As to vegetation all things look promising. The oak and elm are both 

 leafing before the ash, giving promise (according to the proverb) of a fine 

 summer. The apple, pear, strawbeny, and late plnm are making a 

 wonderful show of blossom, and in the liedges the blackthorn has made 

 a good show. 



