326 Howe: Observations on the 



remarked by Solms-Laubach, the calcareous matter seems to en- 

 velop each spore separately like a shell, with a definite though 

 commonly irregular boundary, and the massula (spicula) is appar- 

 ently formed by the cohesion of these shells. Empty interstices, 

 triangular or varied in form, are often to be seen among adjacent 

 shells. Solms-Laubach inclines to the view that a sort of slime 

 is formed from the outer surface of the spore-wall and that the 

 lime is deposited in this, a cuticle being afterwards reformed inside 

 the shell of lime. An alternative supposition, namely, that the 

 lime is first deposited in a residual substance left in the sporangium 

 after the formation of the spores, seemed to him less probable on 

 account of the peculiar distribution of the lime. With the hope 

 of throwing a little more light on this point, we have made an 

 effort to see the spores in the earlier stages of development, using 

 both dry material and that preserved in formalin. We are confi- 

 dent that in the great majority of cases, at least, the lime first 

 appears as a very delicate coating on the outer surface of the 

 spore-wall and that this coating gradually increases in thickness. 

 The presence of a coating of slime or mucilage could not be dem- 

 onstrated with certainty at any stage, though the ordinary mucilage 

 tests were employed. Nevertheless, certain optical appearances 

 give ground for the suspicion that something of the kind is present. 

 The few cases in which the lime seemed to make its first appear- 

 ance in a possible residual matter of the sporangium could be 

 attributed to a disturbance of the natural relations in manipulating 

 the specimen. The sporangium walls are more or less calcified 

 and opaque when the formation of the spores begins and it there- 

 fore becomes necessary to remove or decalcify the walls before a 

 clear view of the contents can be obtained, but decalcification is 

 naturally out of the question when the mode of origin of the cal- 

 careous shells of the spores is the point under investigation. 



3. Developmental. — It was noted by Strasburger* in 1 877 that 

 Acetabulum Androsace (Pallas) Kuntze \_Acetabidaria Mediterranea 

 Lamx.] has a perennial basal portion consisting of rhizoids densely 

 filled with reserve food materials. Similar rhizoidal reservoirs 

 which apparently persist are now found in Acicularia Schcncku 



(Fig. 



0- 



Bot. 



Zeit. 



35' 



715- 







# 



-718. 



1877. 



