242 



Methods in Plant Histology 



extremely hard. Sporocarps for germinating should not be collected 

 until there have been one or two sharp frosts. The sporocarps should 

 be allowed to dry gradually, after which they may be kept in a box 

 until needed for use. They seem to retain their power of germina- 

 tion almost indefinitely. Sporocarps from poisoned herbarium 

 material fifty years old have germinated readily. Even sporocarps 

 which had been preserved in 95 per cent alcohol for several years have 

 been known to germinate. 



To germinate sporocarps, cut away a portion of the hard wall 

 along the front edge and place the sporocarp in a dish of water. The 



gelatinous ring with its sori 

 will sometimes come out in 

 a few minutes. In less than 

 24 hours the microspores, 

 starting from the one-cell 

 stage, will produce the 

 mature sperms. The de- 

 velopment of the mega- 

 spore is equally rapid. 

 Embryos are abundant in 2 

 or 3 days. To secure a 

 series of stages in the de- 

 velopment of the gameto- 

 phytes and embryo, it is 

 necessary to fix material at 

 short intervals. 



For sections showing the development of the antheridium and 

 sperms, it is better to remove the megaspores from the sorus, since 

 they occasion considerable difficulty in cutting. Cut 2 to 5 ju in 

 thickness and stain in iron-haematoxylin. 



The older megaspores are hard to cut. It will facilitate infiltra- 

 tion and cutting if you prick each megaspore with a sharp needle 

 before fixing. Since the archegonium is at the apex of the megaspore, 

 the pricking need do no damage. With good infiltration and Land's 

 cooling device, smooth ribbons can be cut, even from such refractory 

 material (Fig. 83). 



FIG. 83. Marsilia quadrifolia: upper portion 

 of megaspore with an archegonium containing 

 a young embryo. X212. 



