COLLECTING AND PRESERVING MATERIAL. 403 



The plants should be fixed in one per cent, chromic acid (or in a 

 saturated solution of picric acid in sea-water) for 12-24 hours, 

 washed in sea-water as described for Chara, and hardened in 40, 

 60 and 80 per cent, alcohol successively, remaining in each 6- 

 24 hours. They may be preserved in the latter. They may also 

 be preserved in formalin. 



Fucus. — All species are marine and any one will serve. The 

 commonest is Fucus vesiculosus (fig. 42), which may be found on 

 rocks between tide marks. It is of olive-brown color, with 

 swollen tips to many of the branches, and bladders in pairs along 

 the thallus. Plants may be obtained fresh at almost any season. 

 Various species of brown sea-weed may be found fresh at the 

 fish stores of all large cities, whither they are sent as packing. 



Mucor or Rhizopus. — Saturate a piece of bread with water and 

 keep it under a bell jar, in a warm place, for a few days. 

 Several species of molds will appear, the most common of which 

 is the black mold, Rhizopus nigricans. This may be recognized 

 by its white fluffy mycelium, on which arise tufts of erect hyphae 

 developing at tips spherical sporangia, at first white, later black. 

 These tufts occur at intervals along a stolon-like hypha. The 

 same mold may be found on rotting vegetables and fruits, 

 especially sweet potatoes and lemons, and may be raised more 

 rapidly on bread by sowing spores. It will be followed by the 

 green mold, Penicilliu?n glaucum, and often later by other 

 species. Since the plants may be grown promptly, the material 

 used should be living. 



Microsphaera or TJncinula or Erysiphe. — Any species of mildew 

 will answer. Microsphczra grows everywhere on the leaves of 

 the cultivated lilac. Erysiphe is abundant on the leaves of blue 

 or white vervain ( Verbena hastata and V. urticczfolia) and many 

 Compositae. Uncinula attacks leaves of many willows. About 

 midsummer, when the fungus has a white powdery aspect, gather 

 leaves and dry them under light pressure. Later, gather leaves 

 of the same species showing yellow and black dots (the fruits) on 

 the mycelium. Preserve in the same way. 



Cystopus portulacae.— This species is abundant throughout the 

 summer on leaves and stems of purslane {Portulaca oleracea) 

 which grows in every garden and cornfield. Another species 

 grows in late spring on shepherd's-purse {Capsella bursa-pastoris) 

 and another on the pigweeds {Amaranthus sp.). Any one will 

 answer. The species on Qipsella {Cystopus candidus) only oc- 



