Chapter XXIV. 



From Callas to Water Star-grasses. 



The fifth and sixtli orders — the pahns and cyclanthuses — 

 are not represented in Minnesota, but the two famiHes of the 

 seventh order are, by a few well-marked species. Here come the 

 plants of the arum family, comprising in Minnesota the jacks-in- 

 the-pulpit, the calla, the skunk-cabbage and the sweet-flag. 

 These are of somewhat different habits and structure, but they 

 agree in producing their flowers upon fleshy spikes subtended 

 or surrounded by peculiar leaves known as spathcs. The com- 

 mon jack-in-the-pulpit, for instance, develops such a fleshy 

 spike of flowers and the spathe encircles the cluster as a cu- 

 rious hood. The spathe in the calla lily of greenhouses 

 forms a white, vase-like chalice beneath the fleshy spike, while 

 in the skunk-cabbage it becomes a livid purple cowl open at 

 one side. In the sweet-flag the spathe is prolonged straight 

 above the apparently lateral fleshy spike and seems like a con- 

 tinuation of the flattened stem. In most of these plants the 

 rootstocks are commonly short and solid and contain a very 

 acrid sap. The unpleasant taste of the Indian turnip is given 

 in part by crystals of lime oxalate enclosed in certain cells of 

 the bulb. 



The fruit of the arums is a berry. Tn the jack-in-the-pulpit 

 the berries are scarlet and mature in the autumn. In the 

 sweet-flag they are crowded together and gelatinous — often 

 failing to mature. All of these plants have special peculiarities 

 of growth that would be interesting to follow in detail and a 

 few points are particularly worthy of attention. If in the curi- 

 ous flower clusters of the skunk-cabbage a thermometer be in- 

 serted, and after fifteen or twenty minutes it be removed and 

 read, it will be found that the temperature may be from five to 

 fifteen degrees higher than that of the surrounding air, showing 



